Optimizing Wastewater Treatment with PVA Gel Beads and Pumice Stones: A Multi-Stage Reactor Approach

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W. Chorey, Shantanu N. Pawar This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5786466/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 14 You are reading this latest preprint version Abstract Wastewater treatment is critical for public health and environmental protection, with materials and methods chosen based on wastewater layout, regulations, and treatment goals. PVA gel beads, a critical ingredient, are porous hydrogels with 95–98% water content and a specific gravity of 1.025 ± 0.01, which makes them perfect for immobilizing microorganisms needed to undergo pollutant breakdown. PVA gel beads' high porosity enhances oxygen and nutrient permeability, encouraging bacterial growth underneath the beads, decreasing biomass sloughing, and creating less extra sludge than older approaches. These beads, which may be used in both nitrification and denitrification operations, are non-biodegradable and effective in treating a variety of industrial pollutants. The manufacturing method includes creating a PVA solution, adding a crosslinking agent, emulsifying, inducing gelation, and filtering the beads. To restore function, the beads are swollen, rinsed, deswelled, crosslinked, and dried. PVA gel beads have several advantages, including successful mixing due to their near-water specific gravity, reduced sludge generation, and compatibility for a wide range of contaminants. However, they do have limits, such as low specificity for contaminants and the requirement for proper disposal after use. Artificial pumice stones, manufactured from cement, silica sand, and aluminium powder, are lightweight and porous, making them useful in building and water filtering. The experimental setup for this wastewater treatment system incorporates both attached and suspended growth techniques, with a lab-scale model using glass sheets for transparency. The system consists of an intake tank, aeration unit, PVA bioreactor, and sedimentation unit. The first research uses PVA gel beads as a biocarrier in the second reactor, with aeration promoting microorganism growth. In the second trial, pumice stones replaced PVA gel beads in the bioreactor. The third research uses PVA gel beads and pumice stones in the aeration and bioreactor units, respectively, to increase treatment efficiency by using both moving bed and fixed bed bioreactor procedures. Wastewater treatment PVA gel beads Artificial pumice stones PVA Bio mass carrier Bioreactor systems Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1 Introduction Wastewater treatment is a key technique that protects human health and the environment by eliminating toxins from wastewater before it is discharged or reused. The composition of wastewater, treatment aims, regulatory requirements, and available resources all have an impact on the materials and methods used in treatment systems. The key considerations include efficiency, reliability, durability, maintenance ease, cost efficiency, safety, compatibility, scalability, environmental friendliness, and compliance with regulations. This holistic method eliminates easier removal of contaminants from the treated water but will comply with regulatory standards, minimize environmental impact, and reduce operating costs. Polyvinyl alcohol gel beads: These are recent materials that have been accepted for use in wastewater treatment processes for immobilizing microbes onto the beads through the structure of the porous hydrogels. Beads: 95–98% water content; specific gravity close to that of water; enormous porosity that allows room for proliferation of beneficial bacteria while highly attenuating biomass sloughing. However, PVA gel beads produce fewer by-products called sludge in comparison with most biological processes, therefore it has emerged as a promising alternative to nitrification and denitrification processes and the removal of various industrial effluents. The various steps in the manufacturing process of PVA gel beads are as follows: preparation of a PVA solution, crosslinking, emulsification, gelation, washing, drying, sizing, and storage. These beads are rejuvenated through processes like swelling, washing, deswelling, crosslinking, and drying, which extend their lifetime and use. Though they have advantages like these, PVA gel beads also have some disadvantages-limited specificity, saturation capacity, and physical stability that must be taken into account in their use. The other material researched in the wastewater treatment process is artificial pumice stone, which retains all the characteristics of natural pumice and is composed of Portland cement, silica sand, lime, fly ash, aluminium powder, and water. It is employed in construction and water filtering to enhance the efficiencies of wastewater treatment systems by increasing their effectiveness. The combination might significantly boost the efficiency of the treatment in attached and suspended growth systems with the capabilities of both approaches towards increasing microbial breakdown of organic waste. This hybrid technique, therefore, provides a more comprehensive approach in dealing with some properties of wastewater. The bioreactor technology experimented with in the article is reported with components that include an inflow tank, aeration reactor, PVA bioreactor, and a sedimentation tank and uses PVA gel beads. It is a laboratory-scale model that may come in handy in detailing out the treatment process by allowing scientists to visualize changes in the surface of PVA gel bead and effectiveness of pollutant removal. The system is supplied with the necessary aeration and mixing elements, enabling the possibility of controlled operation and optimization of the treatment process. Additionally, the paper deals with the efficiency of PVA gel beads and pumice stone in the bioreactor to prove how different medium for biocarrier exerts influence on the efficiency of treatment. This work highlights the possibility of using innovating materials and complex treatment systems for water and wastewater treatment. 2 Problem Statement This paper addresses the treatment of increasingly large volumes of treated domestic wastewaters with high organic pollutant, suspended solid, and heavy metal concentrations that pose a serious threat to health conditions amongst public and ecological conditions. It has certain drawbacks associated with conventional treatments, including huge sludge and energy-consuming processes. The investment is significant in building large infrastructures. The treatment facilities, on one hand, have to meet the highest regulatory standards, and on the other hand, need to reduce environmental impact and minimize operation costs. The current study involves PVA gel beads and pumice stone as bio-carrier media in a combined attached and suspended growth system for the treatment of domestic wastewater. Its purpose is to eliminate the impurities by designs of new materials and treatments hence efficiently eliminating the 'baggage' usually associated with biological treatment processes. 3 Literature Survey The need for methyl orange (MO) dye, a hazardous contaminant, to be effectively treated has been noted by Asranudin et al. [ 1 ]. In order to solve this, the article uses immobilized Ralstonia pickettii bacteria for bio-decolorization of MO in a PVA–alginate–hectorite matrix (BHec-RP). The study shows that immobilized bacteria perform better at breaking down MO than free cells in both the adsorption and degradation kinetics, which are assessed using dead and living cells, respectively. Important enzymes are used in the process, which breaks down molecules. This is verified by LC-QTOF/MS analysis, which demonstrates the procedure's increased dye removal efficiency. Ali Partovinia et al. [ 2 ] recognized the issue as the ineffective use of biological techniques to remove phenol from industrial effluent, especially at high quantities. In order to address this, the authors investigate how microbial growth rate and phenol biodegradation efficiency are affected by the size of immobilized microbial cell beads. For cell immobilization, they employed an electrospray approach to generate alginate/PVA beads. They discovered that, as a result of increased mass transfer, smaller beads removed phenol better. Removal rose from 15% to 25–34% at 2000 mg/L of phenol, suggesting better performance than free cell systems. Environmental toxicity and phosphorus shortage necessitate effective recovery techniques. In order to solve this, Pingguo Wu et al. [ 3 ] created OSP-loaded cellulose gel beads (OSP@Gel) for the recovery of phosphate from water utilizing cotton fibers and unmodified oyster shell powder. OSP loading on the gel matrix was validated by FT-IR, SEM, and XPS characterization techniques. Under ideal circumstances, the adsorption capacity was 8.80 ± 0.32 mg, and kinetic and isotherm studies suited the Langmuir and PSO models. Thermodynamic research revealed endothermic adsorption, and the mechanical stability and degradability of OSP@Gel demonstrated significant promise for phosphate recovery. The problem of employing Rhodococcus rhodochrous ATCC 21198 immobilized in poly(vinyl)-alcohol–alginate (PVA-AG) hydrogel beads for in situ bioremediation of cis-1,2-dichloroethylene (cDCE) in groundwater is examined in the work of Conor G. Harris et al. [ 4 ]. The challenge is to maximize the mechanical strength and metabolic activity of the bead over time. The authors optimized bead compositions and forecasted compressive strength, oxygen consumption, and hydrolysis rates using a design of experiments methodology. After 30 days, the modified beads dramatically reduced cDCE while exhibiting a high compressive modulus and lower-than-expected metabolic activity. The leakage of synthetic dyes like Methylene Blue (MB) into water bodies can have detrimental impacts on the ecosystem, making the problem of industrial dye wastewater a serious environmental concern. In order to overcome this, Badzlin Nabilah et al. [ 5 ] suggested immobilizing a culture of Ralstonia pickettii and Trichoderma viride combined in a matrix of sodium alginate, polyvinyl alcohol, and bentonite (SA-PVA-Bentonite). In 48 hours at 30°C, they were able to obtain a 97.88% MB decolorization rate by using the entrapment approach. The matrix's capacity for efficient MB decolorization and degradation was demonstrated by LC-MS's identification of degraded metabolites and SEM-EDX's confirmation of culture aggregation. The difficulty of manufacturing ZnO nanoparticles (NPs) inside a chitosan (CS) matrix to produce antibacterial composites with better dispersion was noted by K. Santiago-Castillo et al. [ 6 ]. In order to solve this issue, the study created ZnO NPs in situ using the sol-gel method and mixed them with polyvinyl alcohol (PVA) to create electrospun fibers. The group produced nanofibers without defects by maximizing the PVA/CS ratio and electrospinning settings. The resultant PVA/ZnO composites showed good mechanical qualities, increased spinnability, and potent antibacterial activity against Staphylococcus aureus and Escherichia coli. Saline irrigation is not always effective in treating periprosthetic joint infections (PJI) because of bacterial retention on contaminated medical equipment, as noted by David C. Markel et al. [ 7 ]. In order to address this, a mouse model of Staphylococcus aureus infection was used to assess locally implanted polyvinyl alcohol (PVA)/bioceramic composites doped with either vancomycin (PVA-VAN-P) or vancomycin plus tobramycin (PVA-VAN/TOB-P). After saline irrigation, PVA-VAN/TOB-P successfully eliminated bacterial infections, with no residues found in tissues. These findings raise the possibility that PVA-VAN/TOB-P might be used to treat pressure injuries more effectively. The growth of antibiotic-resistant bacterial infections is the issue noted by Pisut Pongchaikul et al. [ 8 ]. The work examines the antibacterial activity of conjugated nitrogen and sulfur-doped carbon dots (NS/CDs) on core/shell mesoporous silica nanostructures (MSN) against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Testing cytotoxicity and biofilm inhibition in a polyvinyl alcohol (PVA) hydrogel is part of the methodology. According to the results, 0.40 M NS/CDs@MSN showed the most antibacterial efficacy and the least amount of cytotoxicity, making it a good option for use in biomedical applications. In order to remove methylene blue (MB) from water, Holilah et al.'s work [ 9 ] uses an efficient and reusable adsorbent. Using nanocellulose that has been extracted from mangosteen peel, mesoporous hectorite, and alginate, a mesoporous nanocellulose-hectorite-alginate bead (B-NcH) composite is created. When the composite's adsorption ability was assessed, B-NcH5 demonstrated a maximum adsorption capacity of 57.59 mg/g and a 98.64% MB removal rate. With good thermodynamic characteristics and reusability across six cycles, the adsorption followed the Freundlich isotherm and the PSO kinetic model. The manufacture of Polyvinyl Alcohol (PVA) nanofibers is limited by the high cost of OEM replacement parts and commercial electrospinning machines such as the Spinboxsystems BASIC KIT (above USD 15,595). Ika Dewi Wijayanti et al. [ 10 ] created an inexpensive in-house electrospinning machine for less than USD 2,000 in order to remedy this. Their method preserved the manufacture of high-quality PVA nanofibers while streamlining operations. The outcomes showed that the novel device successfully generated nanofibers with superior qualities, providing an affordable substitute for more uses. A unique core-shell hydrogel bead was created in the research of Xiaoyu Chen [ 11 ] to solve the problem of efficiently eliminating methylene blue dye from aqueous solutions. The shell was built of chitosan/activated carbon, while the core was cross-linked with calcium ions and consisted of attapulgite nanofibers and sodium alginate-g-polyacrylamide. The strategy paired the shell's increased adsorption capacity with the core's high-water intake. The findings demonstrated that the core-shell structure outperformed the core alone in terms of adsorption capacity, effectively eliminating methylene blue via a dual adsorption process. Mohamed Mahmoud E. Breky et al. [ 12 ] tackled the problem of eliminating cobalt (Co2+) and hexavalent chromium (Cr6+) ions from wastewater in their investigation. Cunninghamella elegans immobilized in sodium alginate–carboxymethyl cellulose (SA–CMC) gel beads and hydrous TiO2 were used by the researchers as adsorbents. They investigated the effects of starting concentration, pH, contact time, and gel ratio optimization on ion removal efficiency. The removal of Cr6 + and Co2 + from C. elegans/SA–CMC gel beads was shown to be as effective as 64% and 60%, respectively, whereas TiO2 gel beads showed removal efficiencies of 65% and 75%. These adsorbents are efficient and reusable for up to three cycles, as the study showed. The efficient removal of Pb(II) and Cr(VI) ions from aqueous solutions is the challenge Zahid Wahaba et al. [ 13 ] address using eco-friendly produced Fe1–x–MnxO3 nanoparticles and Fe1–x–MnxO3/PVA nanocomposites. The method uses FTIR and UV-visible spectroscopy to confirm the stabilizing effect of Zanthoxylum armatum extract. For characterisation, X-ray diffraction and transmission electron microscopy were used in the investigation. The highest efficiencies of 84% and 92%, respectively, were achieved by optimum adsorption for Pb(II) at pH 5 and Cr(VI) at pH 3. The adsorption data was fitted with Langmuir/Freundlich isotherms and pseudo-second-order kinetics. Controlling drug release patterns from responsive polyelectrolyte network microgels used in liver cancer therapy is an issue that Marcus Wanselius et al. [ 14 ] found. Using a microfluidic system, their method comprised examining the loading and release characteristics of doxepin, chlorpromazine, and amitriptyline in DCbeadTM, hyaluronate, and polyacrylate microgels. They discovered that the essential micelle concentration and network chain charge density of the medicines affected the drug binding strength. The release rates were consistent with the anticipated depletion layer mechanism, indicating the promise of the microgels as amphiphilic drug delivery systems and the efficacy of the microfluidic approach for in vitro investigations. Using a tubular co-flow reactor, Juan Ferrer et al. [ 15 ] tackled the problem of increasing macroporous polymer bead manufacturing rates. Their method involves using methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) monomers to polymerize high internal phase emulsions (M/HIPEs) and water-in-oil (W/O) media. In situ UV polymerization of the continuous phase of the emulsion droplets resulted in poly(MMA-co-EGDMA) beads with an interconnected pore structure and a protective crust. After 24 hours, HCl-loaded beads retained 60% of the HCl, indicating good encapsulation and possible use as delivery systems. 4 Methodology 4.1 Material and Methods Used 4.1.1 Making of PVA Gel Beads for Wastewater Treatment PVA (polyvinyl alcohol) gel beads (Fig. 2 A) are synthetic polymer hydrogels that act as excellent carriers for microorganisms that degrade environmental contaminants. These beads have a porous structure and contain 95–98% water, making them perfect for biological activities. The beads are 150–400 µm in diameter and have a specific gravity of 1.025 ± 0.01, allowing them to stay suspended in water with minimum energy consumption. This makes them very suitable for use in wastewater treatment systems. The microbial organisms can penetrate and growth on/within PVA gel beads because of their substantial porosity whose pore diameters range approximately 20 microns in diameter. Such novel design has the added benefits of minimizing biomass sloughing with excellent treatment effectiveness [ 16 ]. High porosity also supports great oxygen and nutrient permeability to the microorganisms which is important for their potential to degrade pollutants. Thus, the overproduced sludge can be reduced in comparison with usual biological treatment procedures by employing PVA gel beads. 4.1.2 Cross-Linking Process of PVA Gel Beads An important step in the strengthening and stabilization of the mechanical strengths of polyvinyl alcohol gel beads is the cross-linking. Glutaraldehyde is added to prepare a homogeneous PVA solution that forms covalent bonds between polymer chains for a stably more durable gel structure. This is very important in the production of a stronger and a more resilient gel. Droplets of this solution are incorporated into the saturated boric acid solution doped with calcium chloride-this serves as a secondary agent for the cross-linking reaction. Pre-emulsification of the cross-linked solution is performed. Solution of NaOH - primarily the alkaline solution - used to prepare the chemical environment by dispersing it in a PVA solution. The droplets are continuously mixed for an hour so that the produced beads remain homogeneous. The droplets of emulsions get gelled where a cross-linked stable network of gel is obtained. This can also be induced by cooling or further chemical reactions [ 17 ]. Then purification comes with a rinse cycle in deionized water so that there can be neutralization of the pH, removal of all residuals of solvents or impurities and therefore cleaning the final beads for use. 4.1.3 Regeneration Process of PVA Gel Beads PVA gel beads are very useful in nitrification and denitrification processes, where they help remove contaminants like nitrogen compounds. They have shown the capacity to remediate a wide variety of industrial pollutants, including heavy metals and organic toxins. Because the beads are stable in water, non-biodegradable, and insoluble, they have a long lifespan and are a cost-effective alternative for wastewater treatment.PVA gel beads change colour as they age, from white to red-brown, indicating microbial activity from Fig. 1 . Treatment systems that use these beads, such as moving bed reactors, benefit from high efficiency and low sludge formation. They also require less space and have lower operating expenses than traditional techniques [ 19 ]. PVA gel beads can work in both aerobic and anaerobic environments, making them suitable for a variety of wastewater treatment applications. Such techniques considerably lower essential wastewater characteristics such as chemical oxygen demand (COD), biological oxygen demand (BOD), and total nitrogen (TN), as well as hazardous compounds such as heavy metals. 4.2 Pumice Stone in Wastewater Treatment Artificial pumice stone, also known as synthetic pumice stone or man-made pumice stone,(Fig. 2 B) is a manufactured product designed to replicate the properties of natural volcanic pumice. While natural pumice forms through volcanic eruptions and consists of frothy volcanic glass, artificial pumice is created using synthetic materials to imitate its lightweight, porous, and abrasive characteristics [ 20 ]. This synthetic version offers a controlled and consistent structure, making it suitable for various industrial and environmental applications, including water filtration and abrasive cleaning, where natural pumice might not be available or uniform in quality. 4.2.1 Raw Materials for Natural Pumice Stone Natural pumice is produced during volcanic eruptions when molten rock rapidly cools, trapping gas bubbles that form a highly porous and lightweight structure. This natural material is formed without any synthetic additives, relying entirely on the volcanic processes that create its unique physical properties [ 21 ]. The porous structure and low density of pumice make it a valuable resource in many industries, particularly in construction, filtration, and cosmetics, due to its natural origin and sustainability. 4.2.2 Physical Properties of Pumice Stone Natural pumice stone because of the extremely large number of air pockets caught in its formation structure, it is considerably light, making it easy to handle and carry. The high porosity of pumice stone, due to well-connected voids, enhances considerably the means of absorbing and filtering pollutants, which makes it an excellent material for the purpose of water treatment. It can be used for considerable periods in various systems because it does not easily wear out nor chemically break. Furthermore, pumice is chemically inert, meaning it does not combine with either water or any other compounds [ 22 ]. This ensures that it never affects the quality of water during filtration, hence a good filtration medium. 4.2.3 Uses of Pumice Stone in Wastewater Treatment Pumice stone is widely used in wastewater treatment due to its versatile and effective properties. It serves as a key component in multi-layer filtration systems, where its porous structure mechanically filters suspended particulates, reducing turbidity in treated water. Also, the largest pore size of pumice is better for the absorption of organic pollutants, heavy metals, and toxic compounds such as phosphorus, ammonia, and nitrate for removing pollutants. In biological filtration, the pumice stone is an excellent material for microbes that degrade organic substances throughout the treatment processes. Generally, it is applied in an aquaculture system for water filtration and purify, and thus is a requirement for maintaining the integrity of water quality and preventing risks of contamination by aquatic species. Source of domestic wastewater treatment starts from the source of origin, which is domestic waste water that occurs from activities conducted within a house, such as toilets, sinks, shower, and the washing machine [ 23 ]. Each source has a specific combination of contaminants, including organic matter, detergents, and pathogens, and therefore there is a proper treatment method that needs to be applied for the safe reuse or disposal of the product. First, it is collected in a 100-liter capacity storage drum. Designed for purposes of this paper, the drum can be viewed as a holding tank for short-term accumulation through which wastewater may be permitted to build up to be treated successively. From the storage drum, it is transferred to a 15-liter inlet tank. From there, it enters a staging area that regulates the flow of water into the treatment system; otherwise, subsequent processes are not efficient, and are overwhelmed. From the inlet tank, wastewater is pumped into the first aeration unit referred to as Reactor 1. The unit has carried with it a water-lined aeration apparatus mainly manufactured to increase the DO levels in the water. Aeration proves quite effective since it will make the water ready for the biological treatment that is forthcoming. It aerates water and adds air into the reactor to maintain elevated oxygen levels required for the existence and growth of aerobic microorganisms that can digest organic material. This aeration also dilutes the wastewater so that the microorganisms will have enough dispersion to get the contaminants they will break down effectively as shown in the flowchart Fig. 3 . After this, it goes to the bioreactor, also called reactor 2. The bioreactor contains PVA, or polyvinyl alcohol, gel beads. Here, biological treatment actually plays the primary role, since within the gel, supported and trapped are microorganisms that cover themselves with a thick layer, to which all sorts of organic matter dissolved in water attach themselves for useful degradation. The microorganisms consume the organic pollutants, changing them into harmless byproducts such as carbon dioxide and water. As these byproducts greatly reduce the organic load, the organic load is highly reduced. After the biological treatment in Reactor 2 is completed, the treated water flows into a sedimentation unit where remaining suspended solids can settle out to further clarify the water [ 24 ]. At this point, the liquid would have been separated from the suspended solid particle by gravity, and the collected water would be as pure and clean as possible. The sludge settled from the water is usually called sludge that may either be treated or disposed of in an environmentally friendly way. The treated wastewater collected after passing through the sedimentation unit would give clean water far cleaner and safer for reuse. The treated water can be used for irrigation, flushing toilets, or industrial processes, and in doing so, save the sake of conserving water and engaging in sustainable practices. Thus, through effective treatment and recycling of wastewater, households can cut down considerably on their environmental footprint and most importantly, conserve fresh water supply, as part of the newer approaches in water management. This immediately addresses water quality priorities, contributes to greater environmental goals, and protects public health. 4.3 Hybrid Biofilm Carriers for Enhanced Wastewater Treatment: A Comparative Analysis of PVA Gel Beads and Pumice Stone In recent years, advancements in wastewater treatment technologies have emphasized the importance of biofilm carriers to support microbial growth for the effective removal of organic pollutants. This study had three separate experiments as shown in Fig. 4 , meant to be used in comparison of the performance of different biofilm carriers: PVA gel beads, pumice stone, and the combined set of both regarding COD, BOD, TSS, and VSS. Initially, PVA gel beads were utilized as the biocarrier in a Moving Bed Biofilm Reactor experiment. Since the bead was of high porosity and large surface area, they proved to be favorable for bacterial colonization; thus, there were significant decreases in organic content and pollutant load. PVA gel beads displayed enhanced microorganism retention and pollutant removal capabilities as indicated by marked reductions in COD, BOD, and suspended solids. It showed good stability and fluidity during the processing process and ensured effective wastewater treatment under lower maintenance requirements [ 25 ]. In the second experiment, pumice stone was used as an alternative biocarrier medium. Although long-term stability along with porous medium structure could favor the adhesion of microorganisms and subsequent biofilm growth; in general, the performance, concerning COD and BOD reduction, has been lower compared to that of PVA gel beads. However, the long durability attached to the pumice stone and cost-effectiveness linked to the material made it a potential candidate for wastewater treatment systems. The third experiment was to see whether it was at all possible to combine both PVA gel beads and pumice stone and work as biocarriers. Because this would successfully put into one the strengths of two materials, this hybrid approach would then go on to give a more balanced and effective treatment system. Characterized by high oxygen and nutrient permeability, PVA gel beads facilitate quick microbial growth, and pumice stone contributes towards the long-term stability of biofilm which further reduces sludge production. Indeed, such a synergistic effect by these two biocarriers resulted in the greatest COD, BOD, TSS, and VSS removals compared with the other studies; therefore, it would most probably be cost-effective and environmentally friendly in wastewater treatment. 5 Results and Analysis 5.1 Working Model for Experimental Setup The next phase of the process occurred in Reactor 1 (Fig. 6.1A, 1 B, 1 C), where the wastewater was subjected to aeration. This reactor was designed to increase the dissolved oxygen (DO) content in the wastewater, providing the necessary environment for the growth of microorganisms. These microorganisms are essential for breaking down organic matter in the wastewater. After aeration, the wastewater moved into Reactor 2, which functioned as a Moving Bed Biofilm Reactor (MBBR). This reactor utilized PVA gel beads as a biofilm carrier, allowing microorganisms to colonize both the surface and interior of the beads. The microorganisms thrived within the reactor, consuming the organic matter as they grew and reproduced, thereby significantly reducing the organic content of the wastewater. The first reactor used PVA gel beads as the biocarrier media in a moving bed biofilm reactor (MBBR). Results indicated a significant reduction in the organic content of the wastewater, such as chemical oxygen demand (COD) and biological oxygen demand (BOD), due to the high efficiency of PVA gel beads in facilitating microorganism growth. The high porosity of the PVA gel beads provided an optimal environment for bacteria colonization, enhancing pollutant removal. The total suspended solids (TSS) and volatile suspended solids (VSS) were also reduced, while the gel beads exhibited excellent fluidity and stability. Then, at the last stage, other organic residues and microbial masses were separated from treated water by being forced to sedimentate in the sedimentation unit. Since their sedimentation here was relatively slow compared to any other unit because of the forces of gravity, then there was the need for a longer detention time. This removed any remaining suspended suspended solids, meaning that the effluent became clear and cleaner. Generally speaking, the first study proved that PVA gel beads in the MBBR system are effective at removing organic pollutants from domestic wastewater. This provided significant reduction of total suspended solids (TSS) and volatile suspended solids (VSS) in the treated wastewater. Gel beads had excellent stability in the treatment process with their overall structure remaining intact hence, ensuring effective retention of microorganisms. This result could characterize PVA gel beads as an efficient medium for the promotion of growth of biofilms, removals of pollutants hence, in wastewater treatment systems. In the second experiment, Fig. 7 , the biocarrier medium inside the reactor was substituted by pumice stone instead of PVA gel beads. The pores of porous pumice stone were occupied by microorganisms and biofilms were formed. Biofilm is supposed to increase the surface area for microorganisms, and thus facilitates metabolism of the microorganism along with the breakdown of organic pollutants into water. In this context, a reduction in COD and BOD occurred. Although the pumice stone was not as effective as the PVA gel beads regarding pollutant removal, it is still effective in regards to its retention of microorganisms and its promotion of long-term biological activity. In the second study, PVA gel beads were replaced by pumice stone as the biocarrier in the reactor. The pumice stone provided a solid surface for the attachment of microorganisms and allowed for biofilm formation. The porous structure of pumice stone supported microbial growth, although its performance was slightly less effective compared to PVA gel beads in terms of COD and BOD reduction. However, the pumice stone demonstrated good long-term stability and was effective in retaining microorganisms over an extended period. The The pumice stone showed robust long-term stability and preserved microorganisms during extended periods of time, demonstrating that it is an efficient solution for wastewater treatment. The removal of COD, BOD showed a bit lower than the first study; nevertheless, it could be an alternative for wastewater treatment, especially benefiting biofilm adhesion and microbial proliferation. In the third study, Fig. 8 reported the treatment system using PVA gel beads followed by pumice stone in series. Reactor I contained PVA gel beads as a biocarrier support, and reactor II involved pumice stone. This combination proved to be the most effective approach, using one material to complement the other's inherent strengths. The biofilm grown on pumice stone beads had the same discharge at 10% and 20%. Similar to PVA gel beads, pumice provided a stable bed for the growing biofilm and supplied a relatively high dispersion of O2 and nutrients. Excellent COD, BOD, TSS, and other pollutant reductions were observed due to the synergy between the two biocarrier media. The combined system also demonstrated reduced sludge production and improved stability, making it a more cost-effective and efficient method for wastewater treatment. The use of both biofilm carriers provided a balanced treatment process, where the high efficiency of PVA gel beads in supporting microbial growth complemented the long-term stability and biofilm retention capabilities of pumice stone. As a result, the third study offered the most promising results for achieving optimal wastewater treatment. 5.2 Calculation of Flow Rate The flow rate formula is used to calculate the volume of fluid passing through a system per unit time. For a volume of 70 liters, where the volume is given in liters and time in hours, converted to minutes and different detention times, such as 18, 20, and 22 hours. Table 1 Calculation of Flowrate for Detention Time (18, 20, 22 hours). Flow Rate Formula Detention Time Calculation Value 18 Hours 70*1000/18*60 64.81 \(\:ml/min\) \(\:Flow\:Rate=\frac{Volume*1000}{Time\left(\text{m}\text{i}\text{n}\right)}ml/min\) 20 Hours 70*1000/20*60 58.33 \(\:ml/min\) 22 Hours 70*1000/22*60 53.03 \(\:ml/min\) These values represent the flow rate at different time intervals, showing how the flow rate decreases as detention time increases. 5.3 Comparative Analysis for BOD and COD for 1st, 2nd and 3rd Study Three different levels of efficiencies in the removal of organic pollutants from effluent are exhibited by three BOD studies. The organic pollutants removal percentage is consistent for all the studies, showing proper treatment throughout the study periods. The first study has impressively high removal percentages at greater than 85% time points, and the removal rates increased from 18 to 22 hours; this suggests good efficiency in pollutant reduction, especially at the 22-hour mark. While percentage removal is still very high, there is more variability and importantly, removal efficiency drops off at the 22-hour mark in some cases, such as Sample 1, at 62.21%. Such variation should be interpreted to mean that conditions in the second study led to less-than-optimal BOD removals for the longer treatment times as shown in Table 2 . Table 2 Determination of Bio-Chemical Oxygen Demand (BOD) 1st Study, 2nd Study and 3rd Study. BOD 1st Study Inffluent Effluent % Removal 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 1 256 292 328 33 31 25 87.11 89.39 92.38 2 249 312 351 36 37 21 85.55 88.15 94.02 3 286 353 324 28 33 28 90.21 90.66 91.36 4 213 326 315 31 28 29 85.45 91.42 90.8 5 294 317 356 29 25 32 90.14 92.12 91.02 BOD 2nd Study Inffluent Effluent % Removal 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 1 286 353 254 60 72 96 79.03 79.61 62.21 2 213 326 241 79 85 76 62.92 73.93 68.47 3 294 317 283 86 81 84 70.75 74.45 70.32 4 256 292 260 94 83 93 63.29 71.58 64.24 5 249 312 269 82 94 87 67.07 69.88 67.66 BOD 3rd Study Inffluent Effluent % Removal 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 1 256 292 260 26 29 24 89.85 90.07 90.77 2 249 312 269 31 32 29 87.56 89.75 89.22 3 286 353 254 25 26 23 91.26 92.64 90.95 4 265 305 284 27 22 21 89.82 92.79 92.61 5 249 316 291 30 24 23 87.96 92.41 92.1 Removal rates are high with values that always come around or above 87%, and up to 92.79% for Sample 4. Compared to the second study, the effluent concentrations of this study appear to be generally lower, which reflects better overall treatment. Again, the third study removal efficiency also shows a better uniformity both between samples and time points, implying stable treatment conditions. In summary, all three studies demonstrate the great removal of BOD, though the first and third displayed higher and more consistent efficiency, particularly at higher treatment times, while the latter one has higher variability, especially towards 22 hours. This can indicate several conditions of operation or influent attributes. The trends of COD removal among the three studies are analyzed differently. In the first case, the COD removal percent was generally high and within uniform values ranging between 82.4% and 95.27%. The highest removal efficiencies were found to be at the 22-h mark, when most samples had their reductions above 90%, indicating optimal treatment conditions over the extended period. Removal efficiency for the second study has greatly decreased as compared to the first study, and percentage removal falls between 70.98% and 81.34%. Though effectiveness improves with increasing treatment times, results here are still less in comparison to the cases of both first and third studies, with possible variations between operational or influent conditions that have been affecting COD breakdown as shown in Table 3 . Table 3 Determination of Chemical Oxygen Demand (COD) 1st Study, 2nd Study and 3rd Study. COD 1st Study Inffluent Effluent % Removal 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 1 432 426 469 225 225 243 92 89.33 93.00 2 456 453 475 250 245 256 82.4 84.89 85.54 3 423 486 489 226 263 253 87.16 84.79 93.28 4 489 456 489 255 245 256 91.76 86.12 91.01 5 413 475 455 215 252 233 92.09 88.49 95.27 COD 2nd Study Inffluent Effluent % Removal 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 1 509 486 523 290 276 289 75.52 76.09 80.97 2 495 510 493 284 285 276 74.3 78.95 78.62 3 456 453 475 255 259 262 78.82 74.9 81.3 4 423 486 489 243 268 273 74.07 81.34 79.12 5 489 456 489 286 261 272 70.98 74.71 79.78 COD 3rd Study Inffluent Effluent % Removal 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 18 hr 20 hr 22 hr 1 456 453 475 234 233 233 94.87 94.42 93.09 2 423 486 489 219 251 255 93.15 92.63 91.76 3 489 456 489 251 237 253 94.82 92.41 93.28 4 486 519 488 251 269 250 93.63 92.94 95.2 5 516 479 531 268 246 271 92.54 94.72 95.94 In the third study, COD removal efficiency is remarkably consistent and high, with values exceeding 91% across most samples. The percentage removal peaks at 95.94%, showcasing exceptional treatment efficacy. Unlike the second study, the third study maintains high removal percentages across all time intervals, with minimal variability. This suggests that the operational conditions in the third study were more favorable for COD reduction, similar to the high performance seen in the first study but with even better consistency. 6 Future Scope The future scope of wastewater treatment technologies, particularly utilizing materials such as PVA gel beads and pumice stone, presents numerous opportunities for advancements in environmental sustainability and efficiency. With the increasing demands related to water scarcity and pollution, a combination of attached growth and suspended growth processes can improve treatment efficiency. Future research will focus on optimizing the design and operational parameters of these systems to achieve maximum pollutant removal rates while minimizing sludge production and energy consumption. The regenerative processes of PVA gel beads can be adjusted and better evaluated to enhance their performance and lifespan, reducing replacement costs. Additionally, investigating advanced monitoring and automation technologies could support real-time operational control, enabling facilities to adapt to changes in wastewater composition and flow rates. Replacing PVA with bio-based or biodegradable materials will help address environmental concerns related to non-biodegradable residues. Furthermore, exploring the potential synergistic effects of combining pumice stone with other biocarrier materials could improve microbial colonization and pollutant degradation rates. As global regulations on wastewater discharge become more stringent, there will be an urgent need to develop cost-effective, space-efficient, and high-performance treatment systems. Achieving these goals will require collaboration among academia, industry, and regulatory bodies to foster innovation and ensure practical implementation, ultimately contributing to water resource management and environmental protection. 7 Conclusion The effectiveness of biological wastewater treatment systems using PVA gel beads and pumice stones as biocarrier media. PVA gel beads, with their high porosity, fluidity, and near-neutral buoyancy, promote optimal colonization of microorganisms that efficiently degrade organic pollutants like COD and BOD, with minimal sludge production. The beads’ ability to function in both aerobic and anaerobic conditions allows for the removal of various contaminants, including heavy metals and nutrients such as nitrogen and phosphorus. Their regenerative capacity further enhances their cost-effectiveness and sustainability, though eventual saturation and replacement remain practical concerns. Pumice stones, on the other hand, offer a lightweight and porous alternative for microbial growth, supporting fixed-bed treatment processes. The study introduces a hybrid system combining PVA gel beads in the aeration tank and pumice stones in the bioreactor, leveraging both media’s strengths. The PVA gel beads ensure efficient oxygen and nutrient permeability for aerobic microorganisms, while the pumice stones provide a stable structure for anaerobic processes. From the above study, PVA gel beads as a biomass carrier have a great potential to treat contaminated domestic wastewater from diverse backgrounds. With proper designing and planning, a PVA gel beads can remove a variety of organic, inorganic and biological contaminants from the house wastewater. The productivity of activated sludge yield from the Treatment of PVA gel beads with a little biomass carrier is quite Compared to traditional wastewater treatment, construction and maintenance cost of treatment plant using PVA gel beads is low as compared to conventional wastewater treatment plant. Also, this treatment can increase the effectiveness of wastewater treatment process. This combined system, utilizing both suspended and attached growth, maximizes surface area for microbial colonization, improving pollutant removal, reducing sludge, and enhancing stability under variable loads. The hybrid approach delivers efficient treatment for a range of contaminants in a compact, scalable setup, offering a cost-effective solution for achieving wastewater treatment goals with minimized environmental impact. Declarations Ethics and Consent to Participate Ethics and Consent to Participate declarations: not applicable. Consent to Participate Not applicable. Competing Interests The authors declare that they have no competing interests. Funding No funding. Author Contribution Ms. N. W. Chorey: Conceptualization, methodology design, preparation of experimental setup, data collection, and analysis. Responsible for drafting the manuscript, including detailed descriptions of the wastewater treatment process using PVA gel beads and artificial pumice stones. Managed correspondence and revisions throughout the research process.Dr. Shantanu N. Pawar: Supervision, guidance in experimental design, and review of the research framework. Contributed to manuscript review and critical analysis of the study findings. Provided academic resources, technical expertise, and validation of research methodologies. Acknowledgement Not applicable. 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Ultrasound-Assisted Encapsulation of Citronella Oil in Alginate/Carrageenan Beads: Characterization and Kinetic Models. ChemEngineering 2023, 7, 10. https://doi.org/10.3390/chemengineering7010010 M. Alvi, T. French, R. Cardell-Oliver, P. Keymer and A. Ward, "Cost Effective Soft Sensing for Wastewater Treatment Facilities," in IEEE Access, vol. 10, pp. 55694–55708, 2022, doi: 10.1109/ACCESS.2022.3177201 . R. M. M. Salem, M. S. Saraya and A. M. T. Ali-Eldin, "An Industrial Cloud-Based IoT System for Real-Time Monitoring and Controlling of Wastewater," in IEEE Access, vol. 10, pp. 6528–6540, 2022, doi: 10.1109/ACCESS.2022.3141977 . Additional Declarations No competing interests reported. Supplementary Files SupplementaryFile.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 04 Mar, 2025 Reviews received at journal 04 Mar, 2025 Reviews received at journal 03 Mar, 2025 Reviews received at journal 01 Mar, 2025 Reviews received at journal 28 Feb, 2025 Reviewers agreed at journal 27 Feb, 2025 Reviews received at journal 24 Feb, 2025 Reviewers agreed at journal 24 Feb, 2025 Reviewers agreed at journal 24 Feb, 2025 Reviewers agreed at journal 24 Feb, 2025 Reviewers invited by journal 24 Feb, 2025 Editor assigned by journal 20 Feb, 2025 Submission checks completed at journal 19 Feb, 2025 First submitted to journal 08 Jan, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5786466","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":418659270,"identity":"318f3cdb-5f73-4238-a544-018e53b04f2a","order_by":0,"name":"N. W. 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Raisoni College of Engineering and Management, Jalgaon","correspondingAuthor":false,"prefix":"","firstName":"Shantanu","middleName":"N.","lastName":"Pawar","suffix":""}],"badges":[],"createdAt":"2025-01-08 07:08:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5786466/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5786466/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":76864365,"identity":"89d89d78-7694-436e-a1e7-fa2b0a248a2e","added_by":"auto","created_at":"2025-02-21 14:12:46","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":185502,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic Representation of the Cross-Linking and Regeneration Process for PVA Gel Beads\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/27d666f9062f06e9c476f2d2.jpg"},{"id":76864358,"identity":"48aabe8a-1a0f-4e6f-b93f-b1fdd4d23a9f","added_by":"auto","created_at":"2025-02-21 14:12:46","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":175794,"visible":true,"origin":"","legend":"\u003cp\u003e(A) PVA Gel Beads, (B) Pumice Stone\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/9a1faa7d9dfb62d24d11fe6d.jpg"},{"id":76864359,"identity":"0b7ad480-f24f-489f-858d-bc7d290d1f46","added_by":"auto","created_at":"2025-02-21 14:12:46","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":151548,"visible":true,"origin":"","legend":"\u003cp\u003eWastewater Treatment Process\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/dc47c3b44004b9d428072b34.jpg"},{"id":76864363,"identity":"d8090be9-7248-4569-855e-3584a7cf9af0","added_by":"auto","created_at":"2025-02-21 14:12:46","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":348492,"visible":true,"origin":"","legend":"\u003cp\u003eSystem Flow for a Comparative Analysis of PVA gel beads and pumice stone\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/02a4f10371b82cf18d4ed845.jpg"},{"id":76864590,"identity":"1749b00c-1f9a-4746-9028-b4b305da8eb5","added_by":"auto","created_at":"2025-02-21 14:20:47","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":205789,"visible":true,"origin":"","legend":"\u003cp\u003eStorage Drum and Inlet Tank\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/e9521e73364e115ac4af950c.jpg"},{"id":76864586,"identity":"01dec2d0-2a54-48e5-b8e3-258356401edf","added_by":"auto","created_at":"2025-02-21 14:20:46","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":202071,"visible":true,"origin":"","legend":"\u003cp\u003e1A Reactor 1 (Aeration Unit), 1B Reactor 2 (Biological Unit), 1C Reactor 3 (Sedimentation Unit)\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/07c78da1b9e60f3e09ca6031.jpg"},{"id":76864584,"identity":"acc483aa-e27a-4f9a-bcbf-37b2d8908bff","added_by":"auto","created_at":"2025-02-21 14:20:46","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":28917,"visible":true,"origin":"","legend":"\u003cp\u003eReactor 2 Filled with Pumice Stone\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/0ce5a2803ee32ec3d20fb644.jpg"},{"id":76865717,"identity":"c0142982-7add-47b0-9bb1-048ff59466d1","added_by":"auto","created_at":"2025-02-21 14:28:47","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":36556,"visible":true,"origin":"","legend":"\u003cp\u003eReactor 1 filled with PVA gel beads \u0026amp; reactor 2 Filled with pumice stone\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/422e8cf8a22cd35b3ec2c5f5.jpg"},{"id":76866211,"identity":"d6313d34-8ab9-461a-859c-fd4a6c3efe02","added_by":"auto","created_at":"2025-02-21 14:36:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2514138,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/31ff1e6f-8718-4673-a6a2-96b9c6998c71.pdf"},{"id":76864360,"identity":"3446053b-4cdc-40bf-9ee6-1f40b30c4c0d","added_by":"auto","created_at":"2025-02-21 14:12:46","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":207560,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryFile.docx","url":"https://assets-eu.researchsquare.com/files/rs-5786466/v1/868ce42c0df1563f8e253f87.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optimizing Wastewater Treatment with PVA Gel Beads and Pumice Stones: A Multi-Stage Reactor Approach","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eWastewater treatment is a key technique that protects human health and the environment by eliminating toxins from wastewater before it is discharged or reused. The composition of wastewater, treatment aims, regulatory requirements, and available resources all have an impact on the materials and methods used in treatment systems. The key considerations include efficiency, reliability, durability, maintenance ease, cost efficiency, safety, compatibility, scalability, environmental friendliness, and compliance with regulations. This holistic method eliminates easier removal of contaminants from the treated water but will comply with regulatory standards, minimize environmental impact, and reduce operating costs. Polyvinyl alcohol gel beads: These are recent materials that have been accepted for use in wastewater treatment processes for immobilizing microbes onto the beads through the structure of the porous hydrogels. Beads: 95\u0026ndash;98% water content; specific gravity close to that of water; enormous porosity that allows room for proliferation of beneficial bacteria while highly attenuating biomass sloughing. However, PVA gel beads produce fewer by-products called sludge in comparison with most biological processes, therefore it has emerged as a promising alternative to nitrification and denitrification processes and the removal of various industrial effluents. The various steps in the manufacturing process of PVA gel beads are as follows: preparation of a PVA solution, crosslinking, emulsification, gelation, washing, drying, sizing, and storage. These beads are rejuvenated through processes like swelling, washing, deswelling, crosslinking, and drying, which extend their lifetime and use. Though they have advantages like these, PVA gel beads also have some disadvantages-limited specificity, saturation capacity, and physical stability that must be taken into account in their use. The other material researched in the wastewater treatment process is artificial pumice stone, which retains all the characteristics of natural pumice and is composed of Portland cement, silica sand, lime, fly ash, aluminium powder, and water. It is employed in construction and water filtering to enhance the efficiencies of wastewater treatment systems by increasing their effectiveness. The combination might significantly boost the efficiency of the treatment in attached and suspended growth systems with the capabilities of both approaches towards increasing microbial breakdown of organic waste. This hybrid technique, therefore, provides a more comprehensive approach in dealing with some properties of wastewater. The bioreactor technology experimented with in the article is reported with components that include an inflow tank, aeration reactor, PVA bioreactor, and a sedimentation tank and uses PVA gel beads. It is a laboratory-scale model that may come in handy in detailing out the treatment process by allowing scientists to visualize changes in the surface of PVA gel bead and effectiveness of pollutant removal. The system is supplied with the necessary aeration and mixing elements, enabling the possibility of controlled operation and optimization of the treatment process. Additionally, the paper deals with the efficiency of PVA gel beads and pumice stone in the bioreactor to prove how different medium for biocarrier exerts influence on the efficiency of treatment. This work highlights the possibility of using innovating materials and complex treatment systems for water and wastewater treatment.\u003c/p\u003e"},{"header":"2 Problem Statement","content":"\u003cp\u003eThis paper addresses the treatment of increasingly large volumes of treated domestic wastewaters with high organic pollutant, suspended solid, and heavy metal concentrations that pose a serious threat to health conditions amongst public and ecological conditions. It has certain drawbacks associated with conventional treatments, including huge sludge and energy-consuming processes. The investment is significant in building large infrastructures. The treatment facilities, on one hand, have to meet the highest regulatory standards, and on the other hand, need to reduce environmental impact and minimize operation costs. The current study involves PVA gel beads and pumice stone as bio-carrier media in a combined attached and suspended growth system for the treatment of domestic wastewater. Its purpose is to eliminate the impurities by designs of new materials and treatments hence efficiently eliminating the 'baggage' usually associated with biological treatment processes.\u003c/p\u003e"},{"header":"3 Literature Survey","content":"\u003cp\u003eThe need for methyl orange (MO) dye, a hazardous contaminant, to be effectively treated has been noted by Asranudin et al. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In order to solve this, the article uses immobilized Ralstonia pickettii bacteria for bio-decolorization of MO in a PVA\u0026ndash;alginate\u0026ndash;hectorite matrix (BHec-RP). The study shows that immobilized bacteria perform better at breaking down MO than free cells in both the adsorption and degradation kinetics, which are assessed using dead and living cells, respectively. Important enzymes are used in the process, which breaks down molecules. This is verified by LC-QTOF/MS analysis, which demonstrates the procedure's increased dye removal efficiency. Ali Partovinia et al. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] recognized the issue as the ineffective use of biological techniques to remove phenol from industrial effluent, especially at high quantities. In order to address this, the authors investigate how microbial growth rate and phenol biodegradation efficiency are affected by the size of immobilized microbial cell beads. For cell immobilization, they employed an electrospray approach to generate alginate/PVA beads. They discovered that, as a result of increased mass transfer, smaller beads removed phenol better. Removal rose from 15% to 25\u0026ndash;34% at 2000 mg/L of phenol, suggesting better performance than free cell systems. Environmental toxicity and phosphorus shortage necessitate effective recovery techniques. In order to solve this, Pingguo Wu et al. [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] created OSP-loaded cellulose gel beads (OSP@Gel) for the recovery of phosphate from water utilizing cotton fibers and unmodified oyster shell powder. OSP loading on the gel matrix was validated by FT-IR, SEM, and XPS characterization techniques. Under ideal circumstances, the adsorption capacity was 8.80\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32 mg, and kinetic and isotherm studies suited the Langmuir and PSO models. Thermodynamic research revealed endothermic adsorption, and the mechanical stability and degradability of OSP@Gel demonstrated significant promise for phosphate recovery. The problem of employing Rhodococcus rhodochrous ATCC 21198 immobilized in poly(vinyl)-alcohol\u0026ndash;alginate (PVA-AG) hydrogel beads for in situ bioremediation of cis-1,2-dichloroethylene (cDCE) in groundwater is examined in the work of Conor G. Harris et al. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The challenge is to maximize the mechanical strength and metabolic activity of the bead over time. The authors optimized bead compositions and forecasted compressive strength, oxygen consumption, and hydrolysis rates using a design of experiments methodology. After 30 days, the modified beads dramatically reduced cDCE while exhibiting a high compressive modulus and lower-than-expected metabolic activity. The leakage of synthetic dyes like Methylene Blue (MB) into water bodies can have detrimental impacts on the ecosystem, making the problem of industrial dye wastewater a serious environmental concern. In order to overcome this, Badzlin Nabilah et al. [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] suggested immobilizing a culture of Ralstonia pickettii and Trichoderma viride combined in a matrix of sodium alginate, polyvinyl alcohol, and bentonite (SA-PVA-Bentonite). In 48 hours at 30\u0026deg;C, they were able to obtain a 97.88% MB decolorization rate by using the entrapment approach. The matrix's capacity for efficient MB decolorization and degradation was demonstrated by LC-MS's identification of degraded metabolites and SEM-EDX's confirmation of culture aggregation. The difficulty of manufacturing ZnO nanoparticles (NPs) inside a chitosan (CS) matrix to produce antibacterial composites with better dispersion was noted by K. Santiago-Castillo et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In order to solve this issue, the study created ZnO NPs in situ using the sol-gel method and mixed them with polyvinyl alcohol (PVA) to create electrospun fibers. The group produced nanofibers without defects by maximizing the PVA/CS ratio and electrospinning settings. The resultant PVA/ZnO composites showed good mechanical qualities, increased spinnability, and potent antibacterial activity against Staphylococcus aureus and Escherichia coli. Saline irrigation is not always effective in treating periprosthetic joint infections (PJI) because of bacterial retention on contaminated medical equipment, as noted by David C. Markel et al. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In order to address this, a mouse model of Staphylococcus aureus infection was used to assess locally implanted polyvinyl alcohol (PVA)/bioceramic composites doped with either vancomycin (PVA-VAN-P) or vancomycin plus tobramycin (PVA-VAN/TOB-P). After saline irrigation, PVA-VAN/TOB-P successfully eliminated bacterial infections, with no residues found in tissues. These findings raise the possibility that PVA-VAN/TOB-P might be used to treat pressure injuries more effectively. The growth of antibiotic-resistant bacterial infections is the issue noted by Pisut Pongchaikul et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The work examines the antibacterial activity of conjugated nitrogen and sulfur-doped carbon dots (NS/CDs) on core/shell mesoporous silica nanostructures (MSN) against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Testing cytotoxicity and biofilm inhibition in a polyvinyl alcohol (PVA) hydrogel is part of the methodology. According to the results, 0.40 M NS/CDs@MSN showed the most antibacterial efficacy and the least amount of cytotoxicity, making it a good option for use in biomedical applications. In order to remove methylene blue (MB) from water, Holilah et al.'s work [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] uses an efficient and reusable adsorbent. Using nanocellulose that has been extracted from mangosteen peel, mesoporous hectorite, and alginate, a mesoporous nanocellulose-hectorite-alginate bead (B-NcH) composite is created. When the composite's adsorption ability was assessed, B-NcH5 demonstrated a maximum adsorption capacity of 57.59 mg/g and a 98.64% MB removal rate. With good thermodynamic characteristics and reusability across six cycles, the adsorption followed the Freundlich isotherm and the PSO kinetic model. The manufacture of Polyvinyl Alcohol (PVA) nanofibers is limited by the high cost of OEM replacement parts and commercial electrospinning machines such as the Spinboxsystems BASIC KIT (above USD 15,595). Ika Dewi Wijayanti et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] created an inexpensive in-house electrospinning machine for less than USD 2,000 in order to remedy this. Their method preserved the manufacture of high-quality PVA nanofibers while streamlining operations. The outcomes showed that the novel device successfully generated nanofibers with superior qualities, providing an affordable substitute for more uses. A unique core-shell hydrogel bead was created in the research of Xiaoyu Chen [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] to solve the problem of efficiently eliminating methylene blue dye from aqueous solutions. The shell was built of chitosan/activated carbon, while the core was cross-linked with calcium ions and consisted of attapulgite nanofibers and sodium alginate-g-polyacrylamide. The strategy paired the shell's increased adsorption capacity with the core's high-water intake. The findings demonstrated that the core-shell structure outperformed the core alone in terms of adsorption capacity, effectively eliminating methylene blue via a dual adsorption process. Mohamed Mahmoud E. Breky et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] tackled the problem of eliminating cobalt (Co2+) and hexavalent chromium (Cr6+) ions from wastewater in their investigation. Cunninghamella elegans immobilized in sodium alginate\u0026ndash;carboxymethyl cellulose (SA\u0026ndash;CMC) gel beads and hydrous TiO2 were used by the researchers as adsorbents. They investigated the effects of starting concentration, pH, contact time, and gel ratio optimization on ion removal efficiency. The removal of Cr6\u0026thinsp;+\u0026thinsp;and Co2\u0026thinsp;+\u0026thinsp;from C. elegans/SA\u0026ndash;CMC gel beads was shown to be as effective as 64% and 60%, respectively, whereas TiO2 gel beads showed removal efficiencies of 65% and 75%. These adsorbents are efficient and reusable for up to three cycles, as the study showed. The efficient removal of Pb(II) and Cr(VI) ions from aqueous solutions is the challenge Zahid Wahaba et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] address using eco-friendly produced Fe1\u0026ndash;x\u0026ndash;MnxO3 nanoparticles and Fe1\u0026ndash;x\u0026ndash;MnxO3/PVA nanocomposites. The method uses FTIR and UV-visible spectroscopy to confirm the stabilizing effect of Zanthoxylum armatum extract. For characterisation, X-ray diffraction and transmission electron microscopy were used in the investigation. The highest efficiencies of 84% and 92%, respectively, were achieved by optimum adsorption for Pb(II) at pH 5 and Cr(VI) at pH 3. The adsorption data was fitted with Langmuir/Freundlich isotherms and pseudo-second-order kinetics. Controlling drug release patterns from responsive polyelectrolyte network microgels used in liver cancer therapy is an issue that Marcus Wanselius et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] found. Using a microfluidic system, their method comprised examining the loading and release characteristics of doxepin, chlorpromazine, and amitriptyline in DCbeadTM, hyaluronate, and polyacrylate microgels. They discovered that the essential micelle concentration and network chain charge density of the medicines affected the drug binding strength. The release rates were consistent with the anticipated depletion layer mechanism, indicating the promise of the microgels as amphiphilic drug delivery systems and the efficacy of the microfluidic approach for in vitro investigations. Using a tubular co-flow reactor, Juan Ferrer et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] tackled the problem of increasing macroporous polymer bead manufacturing rates. Their method involves using methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) monomers to polymerize high internal phase emulsions (M/HIPEs) and water-in-oil (W/O) media. In situ UV polymerization of the continuous phase of the emulsion droplets resulted in poly(MMA-co-EGDMA) beads with an interconnected pore structure and a protective crust. After 24 hours, HCl-loaded beads retained 60% of the HCl, indicating good encapsulation and possible use as delivery systems.\u003c/p\u003e"},{"header":"4 Methodology","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Material and Methods Used\u003c/h2\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e4.1.1 Making of PVA Gel Beads for Wastewater Treatment\u003c/h2\u003e \u003cp\u003ePVA (polyvinyl alcohol) gel beads (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA) are synthetic polymer hydrogels that act as excellent carriers for microorganisms that degrade environmental contaminants. These beads have a porous structure and contain 95\u0026ndash;98% water, making them perfect for biological activities. The beads are 150\u0026ndash;400 \u0026micro;m in diameter and have a specific gravity of 1.025\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01, allowing them to stay suspended in water with minimum energy consumption. This makes them very suitable for use in wastewater treatment systems. The microbial organisms can penetrate and growth on/within PVA gel beads because of their substantial porosity whose pore diameters range approximately 20 microns in diameter. Such novel design has the added benefits of minimizing biomass sloughing with excellent treatment effectiveness [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. High porosity also supports great oxygen and nutrient permeability to the microorganisms which is important for their potential to degrade pollutants. Thus, the overproduced sludge can be reduced in comparison with usual biological treatment procedures by employing PVA gel beads.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e4.1.2 Cross-Linking Process of PVA Gel Beads\u003c/h2\u003e \u003cp\u003eAn important step in the strengthening and stabilization of the mechanical strengths of polyvinyl alcohol gel beads is the cross-linking. Glutaraldehyde is added to prepare a homogeneous PVA solution that forms covalent bonds between polymer chains for a stably more durable gel structure. This is very important in the production of a stronger and a more resilient gel. Droplets of this solution are incorporated into the saturated boric acid solution doped with calcium chloride-this serves as a secondary agent for the cross-linking reaction. Pre-emulsification of the cross-linked solution is performed. Solution of NaOH - primarily the alkaline solution - used to prepare the chemical environment by dispersing it in a PVA solution. The droplets are continuously mixed for an hour so that the produced beads remain homogeneous. The droplets of emulsions get gelled where a cross-linked stable network of gel is obtained. This can also be induced by cooling or further chemical reactions [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Then purification comes with a rinse cycle in deionized water so that there can be neutralization of the pH, removal of all residuals of solvents or impurities and therefore cleaning the final beads for use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e4.1.3 Regeneration Process of PVA Gel Beads\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePVA gel beads are very useful in nitrification and denitrification processes, where they help remove contaminants like nitrogen compounds. They have shown the capacity to remediate a wide variety of industrial pollutants, including heavy metals and organic toxins. Because the beads are stable in water, non-biodegradable, and insoluble, they have a long lifespan and are a cost-effective alternative for wastewater treatment.PVA gel beads change colour as they age, from white to red-brown, indicating microbial activity from Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Treatment systems that use these beads, such as moving bed reactors, benefit from high efficiency and low sludge formation. They also require less space and have lower operating expenses than traditional techniques [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. PVA gel beads can work in both aerobic and anaerobic environments, making them suitable for a variety of wastewater treatment applications. Such techniques considerably lower essential wastewater characteristics such as chemical oxygen demand (COD), biological oxygen demand (BOD), and total nitrogen (TN), as well as hazardous compounds such as heavy metals.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Pumice Stone in Wastewater Treatment\u003c/h2\u003e \u003cp\u003eArtificial pumice stone, also known as synthetic pumice stone or man-made pumice stone,(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) is a manufactured product designed to replicate the properties of natural volcanic pumice. While natural pumice forms through volcanic eruptions and consists of frothy volcanic glass, artificial pumice is created using synthetic materials to imitate its lightweight, porous, and abrasive characteristics [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. This synthetic version offers a controlled and consistent structure, making it suitable for various industrial and environmental applications, including water filtration and abrasive cleaning, where natural pumice might not be available or uniform in quality.\u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e4.2.1 Raw Materials for Natural Pumice Stone\u003c/h2\u003e \u003cp\u003eNatural pumice is produced during volcanic eruptions when molten rock rapidly cools, trapping gas bubbles that form a highly porous and lightweight structure. This natural material is formed without any synthetic additives, relying entirely on the volcanic processes that create its unique physical properties [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The porous structure and low density of pumice make it a valuable resource in many industries, particularly in construction, filtration, and cosmetics, due to its natural origin and sustainability.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e4.2.2 Physical Properties of Pumice Stone\u003c/h2\u003e \u003cp\u003eNatural pumice stone because of the extremely large number of air pockets caught in its formation structure, it is considerably light, making it easy to handle and carry. The high porosity of pumice stone, due to well-connected voids, enhances considerably the means of absorbing and filtering pollutants, which makes it an excellent material for the purpose of water treatment. It can be used for considerable periods in various systems because it does not easily wear out nor chemically break. Furthermore, pumice is chemically inert, meaning it does not combine with either water or any other compounds [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. This ensures that it never affects the quality of water during filtration, hence a good filtration medium.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e4.2.3 Uses of Pumice Stone in Wastewater Treatment\u003c/h2\u003e \u003cp\u003ePumice stone is widely used in wastewater treatment due to its versatile and effective properties. It serves as a key component in multi-layer filtration systems, where its porous structure mechanically filters suspended particulates, reducing turbidity in treated water.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAlso, the largest pore size of pumice is better for the absorption of organic pollutants, heavy metals, and toxic compounds such as phosphorus, ammonia, and nitrate for removing pollutants. In biological filtration, the pumice stone is an excellent material for microbes that degrade organic substances throughout the treatment processes. Generally, it is applied in an aquaculture system for water filtration and purify, and thus is a requirement for maintaining the integrity of water quality and preventing risks of contamination by aquatic species. Source of domestic wastewater treatment starts from the source of origin, which is domestic waste water that occurs from activities conducted within a house, such as toilets, sinks, shower, and the washing machine [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEach source has a specific combination of contaminants, including organic matter, detergents, and pathogens, and therefore there is a proper treatment method that needs to be applied for the safe reuse or disposal of the product. First, it is collected in a 100-liter capacity storage drum. Designed for purposes of this paper, the drum can be viewed as a holding tank for short-term accumulation through which wastewater may be permitted to build up to be treated successively. From the storage drum, it is transferred to a 15-liter inlet tank. From there, it enters a staging area that regulates the flow of water into the treatment system; otherwise, subsequent processes are not efficient, and are overwhelmed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFrom the inlet tank, wastewater is pumped into the first aeration unit referred to as Reactor 1. The unit has carried with it a water-lined aeration apparatus mainly manufactured to increase the DO levels in the water. Aeration proves quite effective since it will make the water ready for the biological treatment that is forthcoming. It aerates water and adds air into the reactor to maintain elevated oxygen levels required for the existence and growth of aerobic microorganisms that can digest organic material. This aeration also dilutes the wastewater so that the microorganisms will have enough dispersion to get the contaminants they will break down effectively as shown in the flowchart Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eAfter this, it goes to the bioreactor, also called reactor 2. The bioreactor contains PVA, or polyvinyl alcohol, gel beads. Here, biological treatment actually plays the primary role, since within the gel, supported and trapped are microorganisms that cover themselves with a thick layer, to which all sorts of organic matter dissolved in water attach themselves for useful degradation. The microorganisms consume the organic pollutants, changing them into harmless byproducts such as carbon dioxide and water. As these byproducts greatly reduce the organic load, the organic load is highly reduced. After the biological treatment in Reactor 2 is completed, the treated water flows into a sedimentation unit where remaining suspended solids can settle out to further clarify the water [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. At this point, the liquid would have been separated from the suspended solid particle by gravity, and the collected water would be as pure and clean as possible. The sludge settled from the water is usually called sludge that may either be treated or disposed of in an environmentally friendly way. The treated wastewater collected after passing through the sedimentation unit would give clean water far cleaner and safer for reuse. The treated water can be used for irrigation, flushing toilets, or industrial processes, and in doing so, save the sake of conserving water and engaging in sustainable practices. Thus, through effective treatment and recycling of wastewater, households can cut down considerably on their environmental footprint and most importantly, conserve fresh water supply, as part of the newer approaches in water management. This immediately addresses water quality priorities, contributes to greater environmental goals, and protects public health.\u003c/p\u003e \u003cp\u003e4.3 \u003cb\u003eHybrid Biofilm Carriers for Enhanced Wastewater Treatment: A Comparative Analysis of PVA Gel Beads and Pumice Stone\u003c/b\u003e\u003c/p\u003e \u003cp\u003eIn recent years, advancements in wastewater treatment technologies have emphasized the importance of biofilm carriers to support microbial growth for the effective removal of organic pollutants.\u003c/p\u003e \u003cp\u003eThis study had three separate experiments as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, meant to be used in comparison of the performance of different biofilm carriers: PVA gel beads, pumice stone, and the combined set of both regarding COD, BOD, TSS, and VSS. Initially, PVA gel beads were utilized as the biocarrier in a Moving Bed Biofilm Reactor experiment. Since the bead was of high porosity and large surface area, they proved to be favorable for bacterial colonization; thus, there were significant decreases in organic content and pollutant load. PVA gel beads displayed enhanced microorganism retention and pollutant removal capabilities as indicated by marked reductions in COD, BOD, and suspended solids. It showed good stability and fluidity during the processing process and ensured effective wastewater treatment under lower maintenance requirements [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the second experiment, pumice stone was used as an alternative biocarrier medium. Although long-term stability along with porous medium structure could favor the adhesion of microorganisms and subsequent biofilm growth; in general, the performance, concerning COD and BOD reduction, has been lower compared to that of PVA gel beads. However, the long durability attached to the pumice stone and cost-effectiveness linked to the material made it a potential candidate for wastewater treatment systems. The third experiment was to see whether it was at all possible to combine both PVA gel beads and pumice stone and work as biocarriers. Because this would successfully put into one the strengths of two materials, this hybrid approach would then go on to give a more balanced and effective treatment system. Characterized by high oxygen and nutrient permeability, PVA gel beads facilitate quick microbial growth, and pumice stone contributes towards the long-term stability of biofilm which further reduces sludge production. Indeed, such a synergistic effect by these two biocarriers resulted in the greatest COD, BOD, TSS, and VSS removals compared with the other studies; therefore, it would most probably be cost-effective and environmentally friendly in wastewater treatment.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"5 Results and Analysis","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e5.1 Working Model for Experimental Setup\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe next phase of the process occurred in Reactor 1 (Fig.\u0026nbsp;6.1A,\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB,\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC), where the wastewater was subjected to aeration. This reactor was designed to increase the dissolved oxygen (DO) content in the wastewater, providing the necessary environment for the growth of microorganisms. These microorganisms are essential for breaking down organic matter in the wastewater. After aeration, the wastewater moved into Reactor 2, which functioned as a Moving Bed Biofilm Reactor (MBBR). This reactor utilized PVA gel beads as a biofilm carrier, allowing microorganisms to colonize both the surface and interior of the beads. The microorganisms thrived within the reactor, consuming the organic matter as they grew and reproduced, thereby significantly reducing the organic content of the wastewater.\u003c/p\u003e \u003cp\u003eThe first reactor used PVA gel beads as the biocarrier media in a moving bed biofilm reactor (MBBR). Results indicated a significant reduction in the organic content of the wastewater, such as chemical oxygen demand (COD) and biological oxygen demand (BOD), due to the high efficiency of PVA gel beads in facilitating microorganism growth. The high porosity of the PVA gel beads provided an optimal environment for bacteria colonization, enhancing pollutant removal. The total suspended solids (TSS) and volatile suspended solids (VSS) were also reduced, while the gel beads exhibited excellent fluidity and stability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThen, at the last stage, other organic residues and microbial masses were separated from treated water by being forced to sedimentate in the sedimentation unit. Since their sedimentation here was relatively slow compared to any other unit because of the forces of gravity, then there was the need for a longer detention time. This removed any remaining suspended suspended solids, meaning that the effluent became clear and cleaner. Generally speaking, the first study proved that PVA gel beads in the MBBR system are effective at removing organic pollutants from domestic wastewater.\u003c/p\u003e \u003cp\u003eThis provided significant reduction of total suspended solids (TSS) and volatile suspended solids (VSS) in the treated wastewater. Gel beads had excellent stability in the treatment process with their overall structure remaining intact hence, ensuring effective retention of microorganisms. This result could characterize PVA gel beads as an efficient medium for the promotion of growth of biofilms, removals of pollutants hence, in wastewater treatment systems.\u003c/p\u003e \u003cp\u003eIn the second experiment, Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the biocarrier medium inside the reactor was substituted by pumice stone instead of PVA gel beads. The pores of porous pumice stone were occupied by microorganisms and biofilms were formed. Biofilm is supposed to increase the surface area for microorganisms, and thus facilitates metabolism of the microorganism along with the breakdown of organic pollutants into water. In this context, a reduction in COD and BOD occurred. Although the pumice stone was not as effective as the PVA gel beads regarding pollutant removal, it is still effective in regards to its retention of microorganisms and its promotion of long-term biological activity.\u003c/p\u003e \u003cp\u003eIn the second study, PVA gel beads were replaced by pumice stone as the biocarrier in the reactor. The pumice stone provided a solid surface for the attachment of microorganisms and allowed for biofilm formation. The porous structure of pumice stone supported microbial growth, although its performance was slightly less effective compared to PVA gel beads in terms of COD and BOD reduction. However, the pumice stone demonstrated good long-term stability and was effective in retaining microorganisms over an extended period.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe The pumice stone showed robust long-term stability and preserved microorganisms during extended periods of time, demonstrating that it is an efficient solution for wastewater treatment. The removal of COD, BOD showed a bit lower than the first study; nevertheless, it could be an alternative for wastewater treatment, especially benefiting biofilm adhesion and microbial proliferation. In the third study, Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e reported the treatment system using PVA gel beads followed by pumice stone in series. Reactor I contained PVA gel beads as a biocarrier support, and reactor II involved pumice stone.\u003c/p\u003e \u003cp\u003eThis combination proved to be the most effective approach, using one material to complement the other's inherent strengths. The biofilm grown on pumice stone beads had the same discharge at 10% and 20%. Similar to PVA gel beads, pumice provided a stable bed for the growing biofilm and supplied a relatively high dispersion of O2 and nutrients. Excellent COD, BOD, TSS, and other pollutant reductions were observed due to the synergy between the two biocarrier media.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe combined system also demonstrated reduced sludge production and improved stability, making it a more cost-effective and efficient method for wastewater treatment. The use of both biofilm carriers provided a balanced treatment process, where the high efficiency of PVA gel beads in supporting microbial growth complemented the long-term stability and biofilm retention capabilities of pumice stone. As a result, the third study offered the most promising results for achieving optimal wastewater treatment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e5.2 Calculation of Flow Rate\u003c/h2\u003e \u003cp\u003eThe flow rate formula is used to calculate the volume of fluid passing through a system per unit time. For a volume of 70 liters, where the volume is given in liters and time in hours, converted to minutes and different detention times, such as 18, 20, and 22 hours.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCalculation of Flowrate for Detention Time (18, 20, 22 hours).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlow Rate Formula\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDetention Time\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCalculation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18 Hours\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70*1000/18*60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e64.81 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:ml/min\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:Flow\\:Rate=\\frac{Volume*1000}{Time\\left(\\text{m}\\text{i}\\text{n}\\right)}ml/min\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20 Hours\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70*1000/20*60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e58.33 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:ml/min\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22 Hours\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70*1000/22*60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53.03 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:ml/min\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThese values represent the flow rate at different time intervals, showing how the flow rate decreases as detention time increases.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e5.3 Comparative Analysis for BOD and COD for 1st, 2nd and 3rd Study\u003c/h2\u003e \u003cp\u003eThree different levels of efficiencies in the removal of organic pollutants from effluent are exhibited by three BOD studies. The organic pollutants removal percentage is consistent for all the studies, showing proper treatment throughout the study periods. The first study has impressively high removal percentages at greater than 85% time points, and the removal rates increased from 18 to 22 hours; this suggests good efficiency in pollutant reduction, especially at the 22-hour mark. While percentage removal is still very high, there is more variability and importantly, removal efficiency drops off at the 22-hour mark in some cases, such as Sample 1, at 62.21%. Such variation should be interpreted to mean that conditions in the second study led to less-than-optimal BOD removals for the longer treatment times as shown in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDetermination of Bio-Chemical Oxygen Demand (BOD) 1st Study, 2nd Study and 3rd Study.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e \u003cp\u003eBOD 1st Study\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eInffluent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eEffluent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003e% Removal\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e20 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e18 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e20 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e22 hr\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e292\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e328\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e87.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e89.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e92.38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e249\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e351\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e85.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e88.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e94.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e286\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e353\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e324\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e90.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e90.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e91.36\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e213\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e326\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e315\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e85.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e91.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e90.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e294\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e317\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e356\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e90.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e91.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBOD 2nd Study\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e\u003cb\u003eInffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003e\u003cb\u003eEffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003e\u003cb\u003e% Removal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e286\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e353\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e254\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e79.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e79.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e62.21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e213\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e326\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e241\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e62.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e73.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e68.47\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e294\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e317\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e283\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e70.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e74.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e70.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e292\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e63.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e71.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e64.24\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e249\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e269\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e67.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e69.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e67.66\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBOD 3rd Study\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e\u003cb\u003eInffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003e\u003cb\u003eEffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003e\u003cb\u003e% Removal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e292\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e89.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e90.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e90.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e249\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e269\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e87.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e89.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e89.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e286\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e353\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e254\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e91.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e90.95\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e265\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e305\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e284\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e89.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e92.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e249\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e316\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e291\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e87.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e92.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eRemoval rates are high with values that always come around or above 87%, and up to 92.79% for Sample 4. Compared to the second study, the effluent concentrations of this study appear to be generally lower, which reflects better overall treatment. Again, the third study removal efficiency also shows a better uniformity both between samples and time points, implying stable treatment conditions. In summary, all three studies demonstrate the great removal of BOD, though the first and third displayed higher and more consistent efficiency, particularly at higher treatment times, while the latter one has higher variability, especially towards 22 hours. This can indicate several conditions of operation or influent attributes.\u003c/p\u003e \u003cp\u003eThe trends of COD removal among the three studies are analyzed differently. In the first case, the COD removal percent was generally high and within uniform values ranging between 82.4% and 95.27%. The highest removal efficiencies were found to be at the 22-h mark, when most samples had their reductions above 90%, indicating optimal treatment conditions over the extended period. Removal efficiency for the second study has greatly decreased as compared to the first study, and percentage removal falls between 70.98% and 81.34%. Though effectiveness improves with increasing treatment times, results here are still less in comparison to the cases of both first and third studies, with possible variations between operational or influent conditions that have been affecting COD breakdown as shown in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDetermination of Chemical Oxygen Demand (COD) 1st Study, 2nd Study and 3rd Study.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e \u003cp\u003eCOD 1st Study\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eInffluent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eEffluent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003e% Removal\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e20 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e18 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e20 hr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e22 hr\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e432\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e426\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e469\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e225\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e225\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e243\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e89.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e93.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e456\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e453\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e245\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e82.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e84.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e85.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e423\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e486\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e226\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e263\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e253\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e87.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e84.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e93.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e456\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e255\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e245\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e91.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e86.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e91.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e413\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e455\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e215\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e252\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e92.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e88.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e95.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCOD 2nd Study\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e\u003cb\u003eInffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003e\u003cb\u003eEffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003e\u003cb\u003e% Removal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e509\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e486\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e523\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e290\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e276\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e289\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e75.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e76.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e80.97\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e495\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e510\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e493\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e284\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e285\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e276\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e74.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e78.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e78.62\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e456\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e453\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e255\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e259\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e262\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e78.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e74.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e81.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e423\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e486\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e243\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e268\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e273\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e74.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e81.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e79.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e456\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e286\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e261\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e272\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e70.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e74.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e79.78\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"10\" nameend=\"c10\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCOD 3rd Study\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003e\u003cb\u003eInffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003e\u003cb\u003eEffluent\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c10\" namest=\"c8\"\u003e \u003cp\u003e\u003cb\u003e% Removal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e18 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e20 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e22 hr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e456\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e453\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e234\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e94.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e94.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e93.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e423\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e486\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e219\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e251\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e255\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e93.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e91.76\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e456\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e251\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e237\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e253\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e94.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e93.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e486\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e519\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e488\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e251\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e269\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e93.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e95.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e516\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e479\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e531\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e268\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e246\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e271\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e92.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e94.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e95.94\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn the third study, COD removal efficiency is remarkably consistent and high, with values exceeding 91% across most samples. The percentage removal peaks at 95.94%, showcasing exceptional treatment efficacy. Unlike the second study, the third study maintains high removal percentages across all time intervals, with minimal variability. This suggests that the operational conditions in the third study were more favorable for COD reduction, similar to the high performance seen in the first study but with even better consistency.\u003c/p\u003e \u003c/div\u003e"},{"header":"6 Future Scope","content":"\u003cp\u003eThe future scope of wastewater treatment technologies, particularly utilizing materials such as PVA gel beads and pumice stone, presents numerous opportunities for advancements in environmental sustainability and efficiency. With the increasing demands related to water scarcity and pollution, a combination of attached growth and suspended growth processes can improve treatment efficiency. Future research will focus on optimizing the design and operational parameters of these systems to achieve maximum pollutant removal rates while minimizing sludge production and energy consumption. The regenerative processes of PVA gel beads can be adjusted and better evaluated to enhance their performance and lifespan, reducing replacement costs. Additionally, investigating advanced monitoring and automation technologies could support real-time operational control, enabling facilities to adapt to changes in wastewater composition and flow rates. Replacing PVA with bio-based or biodegradable materials will help address environmental concerns related to non-biodegradable residues. Furthermore, exploring the potential synergistic effects of combining pumice stone with other biocarrier materials could improve microbial colonization and pollutant degradation rates. As global regulations on wastewater discharge become more stringent, there will be an urgent need to develop cost-effective, space-efficient, and high-performance treatment systems. Achieving these goals will require collaboration among academia, industry, and regulatory bodies to foster innovation and ensure practical implementation, ultimately contributing to water resource management and environmental protection.\u003c/p\u003e"},{"header":"7 Conclusion","content":"\u003cp\u003eThe effectiveness of biological wastewater treatment systems using PVA gel beads and pumice stones as biocarrier media. PVA gel beads, with their high porosity, fluidity, and near-neutral buoyancy, promote optimal colonization of microorganisms that efficiently degrade organic pollutants like COD and BOD, with minimal sludge production. The beads\u0026rsquo; ability to function in both aerobic and anaerobic conditions allows for the removal of various contaminants, including heavy metals and nutrients such as nitrogen and phosphorus. Their regenerative capacity further enhances their cost-effectiveness and sustainability, though eventual saturation and replacement remain practical concerns.\u003c/p\u003e \u003cp\u003ePumice stones, on the other hand, offer a lightweight and porous alternative for microbial growth, supporting fixed-bed treatment processes. The study introduces a hybrid system combining PVA gel beads in the aeration tank and pumice stones in the bioreactor, leveraging both media\u0026rsquo;s strengths. The PVA gel beads ensure efficient oxygen and nutrient permeability for aerobic microorganisms, while the pumice stones provide a stable structure for anaerobic processes. From the above study, PVA gel beads as a biomass carrier have a great potential to treat contaminated domestic wastewater from diverse backgrounds. With proper designing and planning, a PVA gel beads can remove a variety of organic, inorganic and biological contaminants from the house wastewater. The productivity of activated sludge yield from the Treatment of PVA gel beads with a little biomass carrier is quite Compared to traditional wastewater treatment, construction and maintenance cost of treatment plant using PVA gel beads is low as compared to conventional wastewater treatment plant. Also, this treatment can increase the effectiveness of wastewater treatment process.\u003c/p\u003e \u003cp\u003eThis combined system, utilizing both suspended and attached growth, maximizes surface area for microbial colonization, improving pollutant removal, reducing sludge, and enhancing stability under variable loads. The hybrid approach delivers efficient treatment for a range of contaminants in a compact, scalable setup, offering a cost-effective solution for achieving wastewater treatment goals with minimized environmental impact.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthics and Consent to Participate\u003c/h2\u003e \u003cp\u003eEthics and Consent to Participate declarations: not applicable.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eConsent to Participate\u003c/h2\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCompeting Interests\u003c/strong\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNo funding.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMs. N. W. Chorey: Conceptualization, methodology design, preparation of experimental setup, data collection, and analysis. Responsible for drafting the manuscript, including detailed descriptions of the wastewater treatment process using PVA gel beads and artificial pumice stones. Managed correspondence and revisions throughout the research process.Dr. Shantanu N. Pawar: Supervision, guidance in experimental design, and review of the research framework. Contributed to manuscript review and critical analysis of the study findings. Provided academic resources, technical expertise, and validation of research methodologies.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003ehttps://zenodo.org/records/14776900\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAsranudin, Adi Setyo Purnomo, Holilah, Didik Prasetyoko, Noureddine El Messaoudi, Alya Awinatul Rohmah, Alvin Romadhoni Putra Hidayat, Riki Subagyo, Adsorption and biodegradation of the azo dye methyl orange using Ralstonia pickettii immobilized in polyvinyl alcohol (PVA)\u0026ndash;alginate\u0026ndash;hectorite beads (BHec-RP), RSC Advances, Volume 14, Issue 26, 2024, Pages 18277\u0026ndash;18290, ISSN 2046\u0026ndash;2069, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/d3ra08692e\u003c/span\u003e\u003cspan address=\"10.1039/d3ra08692e\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAli Partovinia, Elham Vatankhah, Investigating the effect of electrosprayed alginate/PVA beads size on the microbial growth kinetics: Phenol biodegradation through immobilized activated sludge, Heliyon, Volume 9, Issue 4, 2023, e15538, ISSN 2405\u0026ndash;8440, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.heliyon.2023.e15538\u003c/span\u003e\u003cspan address=\"10.1016/j.heliyon.2023.e15538\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePingguo Wu, Jiyan Zhong, Naisi Liang, Chanyan Li, Qingyue Cao, Mingjuan Zhao, Yong Li, Mingneng Liao, Chuanming Yu, Oyster shell powder-loaded cellulose gel beads as a high-efficiency adsorbent for phosphorus recovery: preparation, kinetics, isotherms and thermodynamic studies\u0026dagger;\u0026dagger;Electronic supplementary information (ESI) available. 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Ali-Eldin, \"An Industrial Cloud-Based IoT System for Real-Time Monitoring and Controlling of Wastewater,\" in IEEE Access, vol. 10, pp. 6528\u0026ndash;6540, 2022, doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1109/ACCESS.2022.3141977\u003c/span\u003e\u003cspan address=\"10.1109/ACCESS.2022.3141977\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Wastewater treatment, PVA gel beads, Artificial pumice stones, PVA Bio mass carrier, Bioreactor systems","lastPublishedDoi":"10.21203/rs.3.rs-5786466/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5786466/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWastewater treatment is critical for public health and environmental protection, with materials and methods chosen based on wastewater layout, regulations, and treatment goals. PVA gel beads, a critical ingredient, are porous hydrogels with 95\u0026ndash;98% water content and a specific gravity of 1.025\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01, which makes them perfect for immobilizing microorganisms needed to undergo pollutant breakdown. PVA gel beads' high porosity enhances oxygen and nutrient permeability, encouraging bacterial growth underneath the beads, decreasing biomass sloughing, and creating less extra sludge than older approaches. These beads, which may be used in both nitrification and denitrification operations, are non-biodegradable and effective in treating a variety of industrial pollutants. The manufacturing method includes creating a PVA solution, adding a crosslinking agent, emulsifying, inducing gelation, and filtering the beads. To restore function, the beads are swollen, rinsed, deswelled, crosslinked, and dried. PVA gel beads have several advantages, including successful mixing due to their near-water specific gravity, reduced sludge generation, and compatibility for a wide range of contaminants. However, they do have limits, such as low specificity for contaminants and the requirement for proper disposal after use. Artificial pumice stones, manufactured from cement, silica sand, and aluminium powder, are lightweight and porous, making them useful in building and water filtering. The experimental setup for this wastewater treatment system incorporates both attached and suspended growth techniques, with a lab-scale model using glass sheets for transparency. The system consists of an intake tank, aeration unit, PVA bioreactor, and sedimentation unit. The first research uses PVA gel beads as a biocarrier in the second reactor, with aeration promoting microorganism growth. In the second trial, pumice stones replaced PVA gel beads in the bioreactor. The third research uses PVA gel beads and pumice stones in the aeration and bioreactor units, respectively, to increase treatment efficiency by using both moving bed and fixed bed bioreactor procedures.\u003c/p\u003e","manuscriptTitle":"Optimizing Wastewater Treatment with PVA Gel Beads and Pumice Stones: A Multi-Stage Reactor Approach","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-21 14:12:42","doi":"10.21203/rs.3.rs-5786466/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-03-04T13:42:53+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-04T13:40:54+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-03T10:01:05+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-01T09:44:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-28T15:48:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"328783862656836994378956842337333046057","date":"2025-02-28T03:29:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-24T23:06:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"86321897671739857401159755531710842787","date":"2025-02-24T22:57:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"290635700775774530546412778742433043300","date":"2025-02-24T09:15:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"2260758846417551181358487637046116409","date":"2025-02-24T08:51:26+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-02-24T06:12:43+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-02-20T06:44:04+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-02-19T06:18:24+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Applied Sciences","date":"2025-01-08T07:01:14+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"81fd24f8-295f-4f60-b43c-b87b22077815","owner":[],"postedDate":"February 21st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-08-08T12:53:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-02-21 14:12:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5786466","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5786466","identity":"rs-5786466","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}