Raw Sewage Treatment by Coagulation/Flocculation and Ozonization

Raw Sewage Treatment by Coagulation/Flocculation and Ozonization | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Raw Sewage Treatment by Coagulation/Flocculation and Ozonization Matheus Caneles Batista Jorge, Karoline Carvalho Dornelas, Adriana Garcia do Amaral, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4870203/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Dec, 2024 Read the published version in Brazilian Journal of Chemical Engineering → Version 1 posted 5 You are reading this latest preprint version Abstract Coagulation/flocculation and ozonation are two treatment methods commonly used for effluents. Coagulation/flocculation destabilizes the charged particles in the medium, causing them to aggregate for subsequent separation through decantation or flotation. On the other hand, ozonation is an advanced oxidative treatment that can be employed for effluent polishing. This study aimed to evaluate the effectiveness of combining coagulation/flocculation and ozonation as an alternative treatment for raw sewage collected at the Curupy treatment station in Sinop, MT. The experiments were conducted in batches, involving seven doses of tannin-based coagulant (ranging from 0 to 300 mg L -1 ) with and without ozonation (for 40 minutes). Parameters such as pH, color, turbidity, UV absorbance (UV abs), chemical oxygen demand (COD), and biochemical oxygen demand (BOD) were measured before and after the treatments. The results demonstrated that the pH values remained relatively unaffected by the treatments. However, ozonation consistently led to superior removal rates compared to non-ozonation for color, turbidity, UV abs, COD, and BOD (with removal percentages of 86, 87, 74, 71, and 55% respectively, compared to 60%, 74, 49, 58, and 36% without ozonation. For color and turbidity, stabilization of removal rates occurred at coagulant dosages above 100-150 mg L -1 , regardless of ozone contact. Overall, the employed treatments ensured that the sewage met the required conditions for discharge into bodies of water and also made it suitable for potential reuse, thanks to the significant clarification of the effluent. The treatments effectively removed suspended and colloidal solids from the sewage as well as dissolved compounds. Clarification Physical-chemical Polishment Tertiary treatment Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. INTRODUCTION Sewage is primarily composed of water (99.9%) with a minor fraction (0.1%) consisting of solid materials, including organic matter, microorganisms, and chemical substances derived from human feces and urine. Additionally, sewage contains substances such as soaps, detergents, phosphates, sulfates, as well as recalcitrant compounds like hormones and drug residues. Fats and minerals are also present (Kich and Böckel 2017). Sewage treatment involves a combination of physical (decantation/sedimentation), chemical (coagulation/flocculation), and biological (aerobic and anaerobic microbiota) processes. These treatments are typically carried out in sewage treatment stations (STSs), which replicate the natural purification capacity of watercourses more efficiently in terms of time and space (Pereira et al. 2020). Coagulation has gained significant acceptance in the treatment of urban and industrial effluents among physical-chemical processes (Pereira et al. 2020). Coagulants have gained popularity over the years due to their effectiveness in removing particulate matter and reducing parameters such as turbidity and solids (Faye et al. 2017; Lima et al. 2020). Coagulants can be of chemical origin (such as aluminum sulfate, ferric chloride, and ferric sulfate) or natural origin (derived from plants, seeds, etc.) (Lima et al. 2020; Silveira et al. 2020). Natural coagulants, particularly those based on tannins, offer advantages over chemical coagulants in terms of sludge generation and volume reduction (Lima et al. 2020; Silveira et al. 2020). However, the selection of a coagulant depends on factors such as efficiency, sludge reuse, and cost-effectiveness. Coagulation/flocculation has demonstrated satisfactory results in effluent treatment, contributing to the removal of turbidity, color, UV 254nm absorbance (UV abs.) (Silva et al. 2022), as well as total solids, chemical and biochemical oxygen demands (COD and BOD), nitrogen, and phosphorus (Gao et al. 2021). Furthermore, a physical-chemical treatment can be combined with other technologies, such as the use of activated carbon as an adsorbent (Bacelo et al. 2020), biological processes (Andrade and Brito 2021), and advanced processes like hydrogen peroxide and ozone (Silveira et al. 2020). Considering alternative techniques for the degradation of organic matter, particularly those that involve slower or more challenging decomposition processes, the most commonly employed treatments involve the use of high potential oxidizing agents such as advanced oxidative processes (AOPs) and ozone (Pinheiro et al. 2019; Trevizani et al. 2019). AOPs are characterized by the generation of hydroxyl radicals (•OH), which possess a high oxidation potential and exhibit promising outcomes in the degradation of recalcitrant compounds (Ameta et al. 2019; Silveira et al. 2020; Wu et al. 2021). These radicals are generated through reactions involving ozone, hydrogen peroxide, ultraviolet or visible irradiation, and catalysts (Araújo et al. 2021). Ozone, with its high reduction power (E0 = 2.08 V) (Araújo et al. 2021; Oliveira et al. 2018), can directly react with molecules or indirectly generate hydroxyl radicals that facilitate the oxidation process (Arimi 2017; Araújo et al. 2021). The oxidation of both organic and inorganic compounds in the presence of ozone occurs through direct reaction (electrophilic attack) at an acidic pH, targeting specific functional groups (Lajayer et al. 2019). At a basic pH, the reaction proceeds indirectly through hydroxyl radicals, which, due to their lower selectivity, react with organic compounds up to 109 times faster than oxidants like hydrogen peroxide (H 2 O 2 ) (Arimi 2017; Ghernaout and Elboughdiri 2020). The application of ozone as an oxidant has yielded positive outcomes, particularly in terms of color and UV absorption removal (Hoffmann et al. 2020), organic material degradation (COD and BOD) (Gomes and Schoenell 2018), and turbidity reduction (Schons et al. 2018). Ozone is typically generated through the corona effect, which involves the passage of atmospheric air (or oxygen) between two electrodes with a significant potential difference, resulting in a high electrical discharge (approximately 10 kV). This discharge causes the dissociation of O 2 molecules, leading to the formation of atomic oxygen, which subsequently reacts with another O 2 molecule to produce ozone (Scandelai et al. 2021). In this context, the present study aims to assess the efficiency of the coagulation/flocculation + ozonation process in treating raw sewage, focusing on the removal of suspended and dissolved elements measured through parameters such as apparent color, turbidity, UV abs, and chemical and biochemical oxygen demands. 2. MATERIAL AND METHODS The test samples were obtained from the Curupy sewage treatment plant located in Sinop, MT. The treatment system of the plant had a capacity to process 0.06 m 3 s − 1 of sewage and comprised upflow anaerobic reactors (UASB) followed by an activated sludge system. Sewage was collected at the desander outlet (raw sewage) and stored in polyethylene containers. After collection, the effluent was taken to the laboratory and stored under refrigeration. The experiments were carried out at the Water and Waste Laboratory (WWL), at the Federal University of Mato Grosso, Sinop Campus. The effluent was initially characterized by determining its pH, color, turbidity, ultraviolet absorbance at 254 nm (UV abs), chemical oxygen demand (COD), and biochemical oxygen demand (BOD). Apparent color, turbidity, and UV abs values were measured using a colorimeter, turbidimeter, and spectrophotometer, respectively. BOD was determined using the incubation method at 20°C for 5 days, while COD was measured using the hot acid digestion method with dichromate (Table 1 ). Table 1 Parameters and analysis methods applied for the initial characterization of sewage Analyzed parameter Unit Method pH - Potentiometric apparent color mg Pt-Co L − 1 Photocolorimetric turbidity NTU Nephelometric Abs UV cm − 1 Spectrophotometric COD mg L − 1 Hot acid digestion with potassium dichromate BOD mg L − 1 Incubation for 5 days at 20°C without seed The characteristics of the sewage (Table 2 ) reveal that it possesses an optimal pH for biological treatment, although it exhibits a high apparent color value, suggesting the presence of solids. The BOD and COD values indicate a moderate level of organic material. These findings emphasize the necessity for sewage treatment prior to its discharge into water bodies. Table 2 Average characteristics of sewage used in treatment. Parameters Initial values pH 7.18 Apparent color (mg Pt Co L − 1 ) 1930.00 Turbidity (NTU) 177.33 UV abs (cm − 1 ) 1.72 COD (mg L − 1 ) 655.56 BOD (mg L − 1 ) 200.89 In coagulation/flocculation processes, the pH values play a crucial role in destabilizing particle loads and influencing the removal of pollutants (Kamiwada et al. 2020). However, since the initial pH value of the raw sewage falls within the ideal range for the action of the coagulant, no adjustments to the pH were made. Regarding ozonation, the degradation of compounds primarily occurs through direct oxidation at an acidic pH. However, at neutral pH, there is an increase in the decomposition of ozone into hydroxyl radicals (OH), leading to enhanced degradation of compounds through indirect oxidation. Therefore, in the ozonation process, removal efficiencies are influenced by both direct reactions (with greater selectivity but less power) and indirect reactions (with lower selectivity but greater power) due to the sample's pH being close to neutral (Ghernaout and Elboughdiri 2020). Thus, both ozone (O 3 ) and the hydroxyl radical (OH) contribute to the removal mechanisms. The experimental process was divided into two stages (Fig. 1 ), namely primary treatment and effluent polishing. 2.1. Step 1 – Primary Treatment: Coagulation/Flocculation Following the initial characterization, the effluent was subjected to the jar test, where various dosages of coagulant were added. Upon completion of the primary treatment, including coagulation, flocculation, and sedimentation, samples were collected for further characterization. A portion of the sample was then used for the subsequent ozonation test (Fig. 1 ). Table 3 outlines the conditions employed during the primary treatment, including the rotational speeds and their corresponding durations. Table 3 Steps and programming for testing in jar test Stage Rotation (rpm) Time (min) Coagulation – fast step 120 2.5 Flocculation – slow step 20 20 Decantation 0 20 2.2. Step 2 - Effluent Polishing through Ozonation Ozone gas was employed for the sewage polishing step. The ozone generator utilized atmospheric air and operated based on the corona effect generation mechanism. Its nominal production capacity was 0.4 g O 3 per hour. To conduct the experimental tests, the iodometric method, as adapted from APHA (2017) and Almeida Junior (2006), was employed. Portions (0.2 L) of effluent were introduced into the reactor. In the ozone capture cylinders, 0.2 L of potassium iodide (KI), with a concentration of 20 g L − 1 , were added. The reactor and the test tubes were covered, and the tests were started at the pre-defined ozonation time. The KI contents were removed from the test tubes and transferred to Erlenmeyers for the quantification of excess ozone (non-reacted), using the iodometric method. This procedure was performed with distilled water for blank tests. The quantification of residual ozone, mass flow, was determined using the following: $$\:{O}_{3res}\left({mg\:min}^{-1}\right)=\frac{V*N*24}{t}$$ 1 Where: V is the volume of sodium thiosulphate used in the potassium iodide titration (mL); N is the normality of sodium thiosulphate (0.1 N); t is the previously determined exposure time (min); 24 is the conversion factor (24000 mEq L per 1000 mL L). The consumed ozone was determined by the difference in the values of gas not consumed by the water (white-B) and by the effluent (Ef) (2). $$\:{O}_{3co}{(mg\:min}^{-1})=\:{O}_{3res}\left(B\right)-{O}_{3res}\left(Ef\right)$$ 2 Where: O 3co is consumed ozone (mg min − 1 ); O 3res (B) is the residual ozone in the blank (mg min − 1 ); O 3res (Ef) is the residual ozone in the effluent test (mg min − 1 ). The experimental design was completely randomized (DIC), in a 7x2 factorial scheme, with 7 concentrations of coagulant (0, 50, 100, 150, 200, 250 and 300 mg L-1) and 2 times of contact with ozone (0 and 40 min), totaling 14 treatments, in triplicate. The results were submitted to analysis of variance (ANOVA), and when statistical difference was detected (p ≤ 0.05), mean and regression tests were used. 3. RESULTS AND DISCUSSION 3.1. Effect of Treatments The analysis of variance revealed significant differences (p ≤ 0.05) for color, turbidity, and COD concerning the sources of variation: coagulant dosages and ozonation time. Additionally, significant differences (p ≤ 0.05) were observed for UV abs and BOD, specifically in relation to the source of variation, ozonation time. However, the interaction between the sources of variation did not yield any significant difference (Table 4 ). The pH value remained unchanged across all treatments, with a slight increase of approximately 11% at the end of the experiments compared to the initial values. Previous studies have shown that tannins do not affect the pH of the effluent as they do not deplete the alkalinity of the medium. Moreover, tannins exhibit a broad range of action within the pH scale, from 4.5 to 8.0 (Silveira et al. 2021). Table 4 Summary of the analysis of variance for the evaluated parameters Factors pH Color Turbidity UV COD BOD Dosage (Dose) 0.8563 0.0000 0.0000 0.0600 0.0280 0.2401 Ozonation time (OT) 0.1598 0.0000 0.0001 0.0001 0.0019 0.0013 Dose X OT 0.4653 0.2902 0.6353 0.6817 0.7744 0.8247 Values less than or equal to 0.0500 classify the treatments as significant at the 5% probability level. For the UV abs parameter, a remarkable removal of 74% was observed when the sewage underwent ozone treatment. This increase in removal was significantly higher compared to the coagulation treatment alone (Table 5 ). Studies by Lima and Abreu (2018) have indicated that the presence of humic and inorganic substances absorbs ultraviolet light. Additionally, Mena et al. (2020); Munyasamy et al. (2020) have observed that UV absorbance indicates the presence of aromatic and unsaturated substances (chromophores). Hence, the removal of UV abs demonstrates the ozone treatment's effectiveness in decomposing aromatic and unsaturated molecules. Since color and UV abs are closely related to the presence of chromophoric substances in the liquid phase (Ghalebizade and Ayati 2016), any modifications in chromophoric compounds can cause noticeable interference in both the visible (color) (Table 6 ) and ultraviolet (abs) ranges (Table 5 ). Regarding BOD, the coagulant treatment resulted in a removal of 36% (Table 5 ). Conversely, the utilization of ozone led to a significant increase in BOD removal, with an average value of 55%. While the achieved removal levels may not be as high as those for parameters such as color and turbidity, ozonation proves to be efficient in reducing the organic load in effluents, preparing them for further treatment. Furthermore, it can be inferred that ozone facilitates the degradation of organic matter, mineralizing more complex molecules and breaking them down into simpler forms that still contribute to BOD. Thus, ozone acts upon the effluent without generating substantial BOD removal. Schons et al. (2018) obtained superior results (86%) in BOD removal compared to the findings presented in this study. The authors employed ozone in treating a combined raw landfill leachate and domestic sewage, with an ozonation time close to 30 hours and an ozone concentration approximately six times greater than that utilized in our research. Table 5 Abs UV and BOD removal as a function of ozonation time, % OT (min) UV abs. BOD 0 49 36 40 74 55 In terms of apparent color, the utilization of ozonation resulted in an impressive removal rate of 86% (Table 6 ). This significant efficiency in removing colloidal and suspended materials clearly demonstrates the effectiveness of ozonation. Moreover, visual observations during the ozonation process revealed noticeable changes in the effluent's color, transitioning from gray to white/transparent (Fig. 2 ). This color transformation aligns with previous findings reported by Silva et al. (2016). Additionally, Muniyasamy et al. (2020) propose that the reduction in color is linked to O 3 attacking the chromophoric carbon double bonds, resulting in the formation of "bleached" molecules like aliphatic acids and aldehydes, which are generally more biodegradable. This ozone-induced breakdown of double bonds generates simpler molecules, aligning with the BOD results obtained. Furthermore, ozone exhibits potential for bleaching effluents, particularly in situations where reuse is a consideration. Analyzing the removal of color in relation to the coagulant dosage (Fig. 3 a), a certain level of stability in removal efficiency (~ 80%) is observed when the dosage exceeds 75 mg/L. However, for coagulant dosages greater than 50 mg/L, removal rates above 70% were achieved. The outcomes for color removal align with the findings of Jawad et al. (2017); Silveira et al. (2021) when treating domestic sewage and surface water, respectively. These studies demonstrate the coagulant's remarkable efficiency in removing particulate matter and further underscore the potential of combining ozone with coagulation/flocculation processes. Table 6 Removal of color, turbidity and BOD as a function of ozonation time, % OT (min) Color Turbidity COD 0 60 74 58 40 86 87 71 In terms of turbidity, an average removal of 87% was achieved when the effluent came into contact with ozone (Table 6 ). However, even without the application of ozone gas, significant removal was observed. This can be attributed to the coagulant's ability to eliminate suspended solids. The turbidity removal values obtained in this study were higher than those reported by Camilo et al. (2019) when assessing the removal of physical attributes from sewage through ozonation. The reduction in turbidity when effluents are exposed to ozone is attributed to the ability of ozone to break down particles and organic compounds with greater mass, converting them into dissolved molecules (Miklos et al. 2018). Regarding the range of coagulant dosages used for turbidity removal (Fig. 3 b), it was noted that a certain stabilization of removal occurred for dosages exceeding 150 mg/L. Oliveira (2016) achieved similar results using tannin in the dosage range of 200 to 250 mg/L at pH 7. Silveira et al. (2020) evaluated tannin coagulant at varying concentrations ranging from 261 mg/L to 1568 mg/L. Their experimental tests showed that the best results were obtained with a natural pH (without pH adjustment), achieving 100% turbidity removal in sanitary effluents. For this experiment, good removals were also observed in the dosage range of 50 mg/L. Both natural and artificial coagulants consist of large molecular chains with positive or negative charges, allowing them to adsorb particles in their vicinity (Zhao et al. 2019). Tannin-based coagulants are widely used for turbidity removal due to their ability to neutralize surface charges of suspended colloids, aiding in agglomeration and sedimentation (Silveira et al. 2021). The behavior of COD removal was similar to that of color and turbidity parameters, with a removal rate of 71% when the effluent was exposed to the oxidizing gas (Table 6 ). The primary treatment targeted the removal of particulate and colloidal COD, while ozonation primarily affected the dissolved COD portion. Hoffmann et al. (2020), studying the effect of ozonation in raw landfill leachate treatment, reported good COD removal at pH 7, a value very similar to the average found in this study (7.18). Lei and Li (2014), when applying ozone in sewage, suggested that a portion of the COD removal may be attributed to the stripping (mass exchange between liquid and gas) of organic gases. In other words, the chemical oxygen demand may have varied due to both ozone oxidation and mass transfer between the liquid (effluent) and gaseous (ozone) phases. COD was also influenced by coagulant dosages (Fig. 3 c), although it did not follow the same stabilization trend observed for color and turbidity. Dosages ranging from 50 to approximately 160 mg/L exhibited better removal rates (70% or more), while at other concentrations, removal rates above 50% were observed. The COD removal results obtained in this study were slightly higher than those reported by Silveira et al. (2020) when evaluating the potential application of physicochemical processes using tannin coagulant and advanced oxidative ozonation in the treatment of sanitary effluents. In their study, the authors achieved 48% COD removal at the optimal tannin concentration of 523 mg/L. Coagulants generate a larger volume of sludge compared to other treatment technologies, resulting in a higher concentration of organic matter in the generated sludge and effectively removing significant amounts of waste from the effluent (Ghalebizade and Ayati, 2016; Kamiwada et al. 2020). With the BOD and COD data, it was possible to estimate the biodegradability (Fig. 4 ) as a function of the primary treatment and the combination of primary and ozone. The results demonstrated variations in the BOD/COD ratio depending on the treatment employed. Coagulant dosages exceeding 250 mg/L for CF and 175 mg/L for CF + O 3 fell below the optimal range indicative of good biodegradability (> 0.5) (Scandelai et al. 2021). Nevertheless, the treatments still led to an improvement in the effluent's biodegradability compared to the raw effluent, which had a BOD/COD ratio of 0.30. 3.2. Consumed Ozone The consumed ozone values exhibited a tendency to increase with higher coagulant dosages (Fig. 5 ). It appears that the addition of the coagulant promotes ozone consumption without proportionally enhancing the removal efficiency of the evaluated parameters (Fig. 3 ). A plausible explanation for this behavior is that the ozone may react with the residual coagulant from the coagulation process. This hypothesis is supported by the drastic clarification observed in the effluent after ozonation. Ozone has the ability to react with a wide range of functional groups, leading to the breakdown of carbon-carbon double bonds and the formation of lower molecular weight by-products (Fonseca et al. 2017; Ikehata and Li, 2018; BELÉ et al. 2021). 3.3. Residual Values The applied treatment demonstrated high removal values for the analyzed parameters, particularly for color and COD. However, it is worth noting that turbidity and BOD are of greater significance, as they indicate the ability of the CF + O 3 combination to meet regulatory standards for discharge (Table 7 ). The residual values of the evaluated parameters were generally lower for the ozone treatment, with the exception of pH. By combining coagulation (dosages above 200 mg/L) with ozone (40 minutes of treatment time), the effluent acquires characteristics suitable for release into water bodies, as demonstrated by BOD removal rates exceeding 60%. Table 7 Residual values obtained for the analyzed parameters of raw and treated effluents as a function of contact with ozone and doses of coagulant Parameters 0 minutes of O3 40 minutes of O3 Eph. gross Eph. Treated Eph. gross Eph. Treated 0 mg L − 1 pH (1) 7.2 7.6 * 7.2 8.2 * Color (mg Pt Co L − 1 ) (2) 1930.0 1698.3 1930.0 744.0 Turbidity (NTU) (3) 177.3 104.6 177.3 65.1 * UV abs. 254nm (cm − 1 ) 1.7 1.2 1.7 0.7 COD (mg L − 1 ) 655.6 337.2 655.6 291.7 BOD (mg L − 1 ) (4) 200.9 156.9 200.9 138.2 50 mg L − 1 pH 7.2 7.7 * 7.2 8.1 * Color (mg Pt Co L − 1 ) 1930.0 808.33 1930.0 265.3 Turbidity (NTU) 177.3 60.9 * 177.3 28.2 * UV abs. 254nm (cm − 1 ) 1.7 0.6 1.7 0.3 COD (mg L − 1 ) 655.6 196.7 655.6 162.8 BOD (mg L − 1 ) 200.9 110.2 200.9 94.7 100 mg L − 1 pH 7.2 8.0 * 7.2 8.1 * Color (mg Pt Co L − 1 ) 1930.0 760.3 1930.0 221.0 Turbidity (NTU) 177.3 55.3 * 177.3 19.2 * UV abs. 254nm (cm − 1 ) 1.7 0.6 1.7 0.3 COD (mg L − 1 ) 655.6 235.6 655.6 137.8 BOD (mg L − 1 ) 200.9 124.6 200.9 95.9 150 mg L − 1 pH 7.2 8.0 * 7.2 8.0 * Color (mg Pt Co L − 1 ) 1930.0 643.3 1930.0 166.3 Turbidity (NTU) 177.3 33.3 * 177.3 8.1 * UV abs. 254nm (cm − 1 ) 1.7 0.6 1.7 0.4 COD (mg L − 1 ) 655.6 227.8 655.6 131.1 BOD (mg L − 1 ) 200.9 114.6 200.9 81.8 200 mg L − 1 pH 7.2 8.1 * 7.2 8.0 * Color (mg Pt Co L − 1 ) 1930.0 478.0 1930.0 182.3 Turbidity (NTU) 177.3 24.7 * 177.3 7.9 * UV abs. 254nm (cm − 1 ) 1.7 0.8 1.7 0.4 COD (mg L − 1 ) 655.6 237.8 655.6 148.3 BOD (mg L − 1 ) 200.9 131.2 200.9 65.1 * 250 mg L − 1 pH 7.2 8.0 * 7.2 8.0 * Color (mg Pt Co L − 1 ) 1930.0 626.0 1930.0 156.7 Turbidity (NTU) 177.3 22.7 * 177.3 12.0 * UV abs. 254nm (cm − 1 ) 1.7 0.8 1.7 0.5 COD (mg L − 1 ) 655.6 376.7 655.6 173.3 BOD (mg L − 1 ) 200.9 141.2 200.9 79.7 * 300 mg L − 1 pH 7.2 7.9 * 7.2 7.9 * Color (mg Pt Co L − 1 ) 1930.0 501.3 1930.0 174.7 Turbidity (NTU) 177.3 24.0 * 177.3 13.9 * UV abs. 254nm (cm − 1 ) 1.7 1.2 1.7 0.5 COD (mg L − 1 ) 655.6 271.1 655.6 175.0 BOD (mg L − 1 ) 200.9 123.8 200.9 65.7 * Caption. Ideal ranges according to CONAMA resolutions 357/2005 and 430/2011 for disposal in class 2 rivers [(1) – (5–9); (2) – (75 mg Pt Co L -1 ); (3) – (100 NTU); (4) – (minimum removal of 60%)]. For UV abs. and COD there are no minimum values. Residuals marked with asterisks (*) highlight values where release standards were achieved after treatment. Several studies have been conducted on the integration of ozone with other advanced oxidation processes (AOPs) and its combination with conventional treatments for polishing purposes (Ikehata and Li 2018; Hidayaturrahman and Lee 2019; Silveira et al. 2020; Sun et al. 2019; Li et al. 2022). The efficiency of biological treatments has been shown to increase when combined with the coagulation/flocculation + ozone + biological treatment sequence (Mella et al. 2018; Scandelai et al. 2021). Additionally, high BOD removals have been achieved by Silva and Daniel (2015) when using ozone followed by chlorine disinfection. Pastore et al. (2018) compared different treatments for landfill leachate and found that the most effective approach was the combination of biological treatment and ozonation, when considering the RBGSB (batch sequential granular biofilter) reactor along with other treatments such as hydrogen peroxide, ultraviolet and hydrogen peroxide, and ozonation. The results presented in this study, along with findings from other researchers, highlight the significant potential of ozonation in effluent treatment. 4. CONCLUSIONS The combination of coagulation/flocculation and ozonation proves to be highly efficient in treating sanitary sewage effluents. Coagulation/flocculation and coagulation/flocculation + ozonation demonstrated remarkable removal rates for apparent color (> 80%), turbidity (~ 87%), and COD (> 71%). However, the highest removal rates for UV abs. (74%) and BOD (55%) were achieved only when ozonation was applied. Declarations AUTHOR CONTRIBUTIONS Conceptualization: Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri and Roselene Maria Schneider; Methodology: Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri and Roselene Maria Schneider; Formal analysis and investigation: Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri, Roselene Maria Schneider and Adriana Garcia do Amaral; Writing - original draft preparation: Matheus Caneles Batista Jorge; Writing - review and editing Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri, Roselene Maria Schneider and Karoline Carvalho Dornelas; Supervision: Milene Carvalho Bongiovani Roveri, Roselene Maria Schneider, Adriana Garcia do Amaral and Karoline Carvalho Dornelas. ACKNOWLEDGEMENTS The authors would like to thank the Institute of Agricultural and Environmental Sciences, Federal University of Mato Grosso (UFMT-Sinop), for the financial support. Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. -Ethical Approval: Not applicable. -Consent to Participate: Not applicable. -Consent to Publish: Not applicable. -Funding: No funding was received to assist with the preparation of this manuscript. -Competing Interests: All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript. References Almeida Junior RL (2006) Redução de cor do licor negro da indústria de celulose de algodão com a utilização de ozônio em meio básico. Dissertation, State University of Campinas Ameta R, Chohadia AK, Jain A, Punjabi PB (2019) Fenton and Photo-Fenton Processes. 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Separation Science and Technology 55(17):3175–3183. https://doi.org/10.1080/01496395.2019.1670209 Trevizani JLB, Carvalho KQ, Passig FH, Schiavon GJ, Pereira IC, Medeiros FVS (2019) Determinação da cinética de ozonização de efluente têxtil na remoção de cor e matéria orgânica. Revista Matéria 24(1): https://doi.org/10.1590/S1517-707620190001.0613 Wu CW, Chen W, Zhepei G, Li Q (2021) A review of the characteristics of Fenton and ozonation systems in landfill leachate treatment. Science of The Total Environment 762: 143131. https://doi.org/10.1016/j.scitotenv.2020.143131 Zhao Z, Sun W, Ray MB, Ray AK, Huang T, Chen J (2019) Optimization and modeling of coagulation-flocculation to remove algae and organic matter from surface water by response surface methodology. Frontiers of Environmental Science & Engineering 13(5):75. https://doi.org/10.1007/s11783-019-1159-7 Supplementary Files floatimage1.jpeg Graphical Abstract Cite Share Download PDF Status: Published Journal Publication published 14 Dec, 2024 Read the published version in Brazilian Journal of Chemical Engineering → Version 1 posted Reviewers agreed at journal 21 Aug, 2024 Reviewers invited by journal 20 Aug, 2024 Editor invited by journal 09 Aug, 2024 Editor assigned by journal 09 Aug, 2024 First submitted to journal 06 Aug, 2024 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. 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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-4870203","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":342787408,"identity":"15bd5e5c-ca0c-4469-a658-dd6ad4442d2a","order_by":0,"name":"Matheus Caneles Batista Jorge","email":"","orcid":"","institution":"UFMT: Universidade Federal de Mato Grosso","correspondingAuthor":false,"prefix":"","firstName":"Matheus","middleName":"Caneles Batista","lastName":"Jorge","suffix":""},{"id":342787409,"identity":"499a6d53-a2c6-4a44-8315-98fc829c8206","order_by":1,"name":"Karoline Carvalho Dornelas","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABB0lEQVRIiWNgGAWjYBACCRDxwABEJoAICwYG9gaGDzAuTi0JCC1APs8BxhlADgEtDMhaJBLwa5FsP/vwQULBHTkG9uRjnwsqJOTlZ74xbLr5gyHPvAG7FmmedGODBINnxgw8z5JnzzgjYbjhdo5hc04CQ7HMAexa5BjS2CQSDA4nNkjkGDPztkkwbpDOMX8M1JI4A4fD5PifgbXUQ7T8k7CfP/MM2BacWqQlILYkMIC1NEgkNtzgwa9FcsYzZqBfDhu2Af3CzHNMInnDmbTC5pw0iWIJHFokzqcxPvjw57A8P3vyYWaeGhvb+e2HNzbn2Njk4dICB2zoZhHSMApGwSgYBaMADwAAq8pTPJlPmaMAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-3780-913X","institution":"UFMT: Universidade Federal de Mato Grosso","correspondingAuthor":true,"prefix":"","firstName":"Karoline","middleName":"Carvalho","lastName":"Dornelas","suffix":""},{"id":342787410,"identity":"bbb71078-f826-42be-8f59-d921b2f40bcb","order_by":2,"name":"Adriana Garcia do Amaral","email":"","orcid":"","institution":"UFMT: Universidade Federal de Mato Grosso","correspondingAuthor":false,"prefix":"","firstName":"Adriana","middleName":"Garcia do","lastName":"Amaral","suffix":""},{"id":342787411,"identity":"cff279b4-efc3-46c8-98b5-eff3edbf8219","order_by":3,"name":"Milene Carvalho Bongiovani Roveri","email":"","orcid":"","institution":"UFMT: Universidade Federal de Mato Grosso","correspondingAuthor":false,"prefix":"","firstName":"Milene","middleName":"Carvalho Bongiovani","lastName":"Roveri","suffix":""},{"id":342787412,"identity":"40641c91-076d-4cb2-b653-ac05eb5b1c16","order_by":4,"name":"Roselene Maria Schneider","email":"","orcid":"","institution":"UFMT: Universidade Federal de Mato Grosso","correspondingAuthor":false,"prefix":"","firstName":"Roselene","middleName":"Maria","lastName":"Schneider","suffix":""}],"badges":[],"createdAt":"2024-08-06 18:03:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4870203/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4870203/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s43153-024-00525-0","type":"published","date":"2024-12-14T15:57:44+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":64752816,"identity":"bfe4aca4-f128-40df-8b9a-53844c32c5d8","added_by":"auto","created_at":"2024-09-18 11:04:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":272304,"visible":true,"origin":"","legend":"\u003cp\u003eScheme of the treatment used in the tests. 1\u003csup\u003est\u003c/sup\u003e Stage – coagulation/flocculation – and 2\u003csup\u003end\u003c/sup\u003e Stage – ozonation – [ozone generator (1), acrylic reactor with porous stone (2), beaker for foam containment (3), beakers for capturing residual ozone with potassium iodide (4 and 5)]\u003c/p\u003e","description":"","filename":"floatimage231.png","url":"https://assets-eu.researchsquare.com/files/rs-4870203/v1/46847c1a58fdc2a5afc1b86b.png"},{"id":64752817,"identity":"f6bfb3fe-3059-481e-8e68-77d2d657a406","added_by":"auto","created_at":"2024-09-18 11:04:45","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":166881,"visible":true,"origin":"","legend":"\u003cp\u003eComparison between the treatments of sanitary sewage effluent, where 2A shows the effluent after coagulation/flocculation, and 2B demonstrates the effluent after ozone polishing\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4870203/v1/9d66ae42f446c859745fb113.jpeg"},{"id":64752811,"identity":"39a00cc6-6ca3-4a8e-a92e-e39c1c779a99","added_by":"auto","created_at":"2024-09-18 11:04:44","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":120132,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in color removal (3a), turbidity (3b) and COD (3c) as a function of the range of coagulant used\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4870203/v1/89a032b841363e8aa5c0795d.jpeg"},{"id":64752813,"identity":"5a6ec830-1a1e-461c-a43a-58796be96c50","added_by":"auto","created_at":"2024-09-18 11:04:44","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":46561,"visible":true,"origin":"","legend":"\u003cp\u003eEstimated behavior of the effluent biodegradability during the experiment\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4870203/v1/38786ba9b8662cadc03f1ab7.jpeg"},{"id":64752814,"identity":"9024dcf0-6f8f-49ba-882d-0be118c3f34d","added_by":"auto","created_at":"2024-09-18 11:04:45","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":86698,"visible":true,"origin":"","legend":"\u003cp\u003eOzone consumption behavior in the effluent test\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4870203/v1/99dbde6e18d70d34c158b0ce.jpeg"},{"id":71552470,"identity":"7053b040-7cd9-4e5c-b45f-51d4ba0b87c0","added_by":"auto","created_at":"2024-12-16 16:06:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1509742,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4870203/v1/a45fe8ce-5c1d-4e0c-b81c-4dd17d322593.pdf"},{"id":64752812,"identity":"423d0f16-6679-437d-9de5-5998b9193633","added_by":"auto","created_at":"2024-09-18 11:04:44","extension":"jpeg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":546606,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical Abstract\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4870203/v1/b91381e2400d52e83ee43edb.jpeg"}],"financialInterests":"","formattedTitle":"\u003cp\u003eRaw Sewage Treatment by Coagulation/Flocculation and Ozonization\u003c/p\u003e","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eSewage is primarily composed of water (99.9%) with a minor fraction (0.1%) consisting of solid materials, including organic matter, microorganisms, and chemical substances derived from human feces and urine. Additionally, sewage contains substances such as soaps, detergents, phosphates, sulfates, as well as recalcitrant compounds like hormones and drug residues. Fats and minerals are also present (Kich and B\u0026ouml;ckel 2017).\u003c/p\u003e \u003cp\u003eSewage treatment involves a combination of physical (decantation/sedimentation), chemical (coagulation/flocculation), and biological (aerobic and anaerobic microbiota) processes. These treatments are typically carried out in sewage treatment stations (STSs), which replicate the natural purification capacity of watercourses more efficiently in terms of time and space (Pereira et al. 2020).\u003c/p\u003e \u003cp\u003eCoagulation has gained significant acceptance in the treatment of urban and industrial effluents among physical-chemical processes (Pereira et al. 2020). Coagulants have gained popularity over the years due to their effectiveness in removing particulate matter and reducing parameters such as turbidity and solids (Faye et al. 2017; Lima et al. 2020).\u003c/p\u003e \u003cp\u003eCoagulants can be of chemical origin (such as aluminum sulfate, ferric chloride, and ferric sulfate) or natural origin (derived from plants, seeds, etc.) (Lima et al. 2020; Silveira et al. 2020). Natural coagulants, particularly those based on tannins, offer advantages over chemical coagulants in terms of sludge generation and volume reduction (Lima et al. 2020; Silveira et al. 2020). However, the selection of a coagulant depends on factors such as efficiency, sludge reuse, and cost-effectiveness.\u003c/p\u003e \u003cp\u003eCoagulation/flocculation has demonstrated satisfactory results in effluent treatment, contributing to the removal of turbidity, color, UV\u003csub\u003e254nm\u003c/sub\u003e absorbance (UV abs.) (Silva et al. 2022), as well as total solids, chemical and biochemical oxygen demands (COD and BOD), nitrogen, and phosphorus (Gao et al. 2021).\u003c/p\u003e \u003cp\u003eFurthermore, a physical-chemical treatment can be combined with other technologies, such as the use of activated carbon as an adsorbent (Bacelo et al. 2020), biological processes (Andrade and Brito 2021), and advanced processes like hydrogen peroxide and ozone (Silveira et al. 2020).\u003c/p\u003e \u003cp\u003eConsidering alternative techniques for the degradation of organic matter, particularly those that involve slower or more challenging decomposition processes, the most commonly employed treatments involve the use of high potential oxidizing agents such as advanced oxidative processes (AOPs) and ozone (Pinheiro et al. 2019; Trevizani et al. 2019).\u003c/p\u003e \u003cp\u003eAOPs are characterized by the generation of hydroxyl radicals (\u0026bull;OH), which possess a high oxidation potential and exhibit promising outcomes in the degradation of recalcitrant compounds (Ameta et al. 2019; Silveira et al. 2020; Wu et al. 2021). These radicals are generated through reactions involving ozone, hydrogen peroxide, ultraviolet or visible irradiation, and catalysts (Ara\u0026uacute;jo et al. 2021).\u003c/p\u003e \u003cp\u003eOzone, with its high reduction power (E0\u0026thinsp;=\u0026thinsp;2.08 V) (Ara\u0026uacute;jo et al. 2021; Oliveira et al. 2018), can directly react with molecules or indirectly generate hydroxyl radicals that facilitate the oxidation process (Arimi 2017; Ara\u0026uacute;jo et al. 2021).\u003c/p\u003e \u003cp\u003eThe oxidation of both organic and inorganic compounds in the presence of ozone occurs through direct reaction (electrophilic attack) at an acidic pH, targeting specific functional groups (Lajayer et al. 2019). At a basic pH, the reaction proceeds indirectly through hydroxyl radicals, which, due to their lower selectivity, react with organic compounds up to 109 times faster than oxidants like hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) (Arimi 2017; Ghernaout and Elboughdiri 2020).\u003c/p\u003e \u003cp\u003eThe application of ozone as an oxidant has yielded positive outcomes, particularly in terms of color and UV absorption removal (Hoffmann et al. 2020), organic material degradation (COD and BOD) (Gomes and Schoenell 2018), and turbidity reduction (Schons et al. 2018).\u003c/p\u003e \u003cp\u003eOzone is typically generated through the corona effect, which involves the passage of atmospheric air (or oxygen) between two electrodes with a significant potential difference, resulting in a high electrical discharge (approximately 10 kV). This discharge causes the dissociation of O\u003csub\u003e2\u003c/sub\u003e molecules, leading to the formation of atomic oxygen, which subsequently reacts with another O\u003csub\u003e2\u003c/sub\u003e molecule to produce ozone (Scandelai et al. 2021).\u003c/p\u003e \u003cp\u003eIn this context, the present study aims to assess the efficiency of the coagulation/flocculation\u0026thinsp;+\u0026thinsp;ozonation process in treating raw sewage, focusing on the removal of suspended and dissolved elements measured through parameters such as apparent color, turbidity, UV abs, and chemical and biochemical oxygen demands.\u003c/p\u003e"},{"header":"2. MATERIAL AND METHODS","content":"\u003cp\u003eThe test samples were obtained from the Curupy sewage treatment plant located in Sinop, MT. The treatment system of the plant had a capacity to process 0.06 m\u003csup\u003e3\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of sewage and comprised upflow anaerobic reactors (UASB) followed by an activated sludge system.\u003c/p\u003e \u003cp\u003eSewage was collected at the desander outlet (raw sewage) and stored in polyethylene containers. After collection, the effluent was taken to the laboratory and stored under refrigeration. The experiments were carried out at the Water and Waste Laboratory (WWL), at the Federal University of Mato Grosso, Sinop Campus.\u003c/p\u003e \u003cp\u003eThe effluent was initially characterized by determining its pH, color, turbidity, ultraviolet absorbance at 254 nm (UV abs), chemical oxygen demand (COD), and biochemical oxygen demand (BOD). Apparent color, turbidity, and UV abs values were measured using a colorimeter, turbidimeter, and spectrophotometer, respectively. BOD was determined using the incubation method at 20\u0026deg;C for 5 days, while COD was measured using the hot acid digestion method with dichromate (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\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\u003eParameters and analysis methods applied for the initial characterization of sewage\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnalyzed parameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMethod\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePotentiometric\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eapparent color\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg Pt-Co L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePhotocolorimetric\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eturbidity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNTU\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNephelometric\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbs UV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ecm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSpectrophotometric\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHot acid digestion with potassium dichromate\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIncubation for 5 days at 20\u0026deg;C without seed\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\u003eThe characteristics of the sewage (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) reveal that it possesses an optimal pH for biological treatment, although it exhibits a high apparent color value, suggesting the presence of solids. The BOD and COD values indicate a moderate level of organic material. These findings emphasize the necessity for sewage treatment prior to its discharge into water bodies.\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\u003eAverage characteristics of sewage used in treatment.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInitial values\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApparent color (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1930.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e177.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.72\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e655.56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e200.89\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 coagulation/flocculation processes, the pH values play a crucial role in destabilizing particle loads and influencing the removal of pollutants (Kamiwada et al. 2020). However, since the initial pH value of the raw sewage falls within the ideal range for the action of the coagulant, no adjustments to the pH were made.\u003c/p\u003e \u003cp\u003eRegarding ozonation, the degradation of compounds primarily occurs through direct oxidation at an acidic pH. However, at neutral pH, there is an increase in the decomposition of ozone into hydroxyl radicals (OH), leading to enhanced degradation of compounds through indirect oxidation. Therefore, in the ozonation process, removal efficiencies are influenced by both direct reactions (with greater selectivity but less power) and indirect reactions (with lower selectivity but greater power) due to the sample's pH being close to neutral (Ghernaout and Elboughdiri 2020). Thus, both ozone (O\u003csub\u003e3\u003c/sub\u003e) and the hydroxyl radical (OH) contribute to the removal mechanisms.\u003c/p\u003e \u003cp\u003eThe experimental process was divided into two stages (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), namely primary treatment and effluent polishing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Step 1 \u0026ndash; Primary Treatment: Coagulation/Flocculation\u003c/h2\u003e \u003cp\u003eFollowing the initial characterization, the effluent was subjected to the jar test, where various dosages of coagulant were added. Upon completion of the primary treatment, including coagulation, flocculation, and sedimentation, samples were collected for further characterization. A portion of the sample was then used for the subsequent ozonation test (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e outlines the conditions employed during the primary treatment, including the rotational speeds and their corresponding durations.\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\u003eSteps and programming for testing in \u003cem\u003ejar test\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStage\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRotation (rpm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTime (min)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCoagulation \u0026ndash; fast step\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlocculation \u0026ndash; slow step\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecantation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Step 2 - Effluent Polishing through Ozonation\u003c/h2\u003e \u003cp\u003eOzone gas was employed for the sewage polishing step. The ozone generator utilized atmospheric air and operated based on the corona effect generation mechanism. Its nominal production capacity was 0.4 g O\u003csup\u003e3\u003c/sup\u003e per hour.\u003c/p\u003e \u003cp\u003eTo conduct the experimental tests, the iodometric method, as adapted from APHA (2017) and Almeida Junior (2006), was employed.\u003c/p\u003e \u003cp\u003ePortions (0.2 L) of effluent were introduced into the reactor. In the ozone capture cylinders, 0.2 L of potassium iodide (KI), with a concentration of 20 g L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, were added. The reactor and the test tubes were covered, and the tests were started at the pre-defined ozonation time.\u003c/p\u003e \u003cp\u003eThe KI contents were removed from the test tubes and transferred to Erlenmeyers for the quantification of excess ozone (non-reacted), using the iodometric method. This procedure was performed with distilled water for blank tests.\u003c/p\u003e \u003cp\u003eThe quantification of residual ozone, mass flow, was determined using the following:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{O}_{3res}\\left({mg\\:min}^{-1}\\right)=\\frac{V*N*24}{t}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere:\u003c/p\u003e \u003cp\u003eV is the volume of sodium thiosulphate used in the potassium iodide titration (mL);\u003c/p\u003e \u003cp\u003eN is the normality of sodium thiosulphate (0.1 N);\u003c/p\u003e \u003cp\u003et is the previously determined exposure time (min);\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e24 is the conversion factor (24000 mEq L per 1000 mL L).\u003c/h3\u003e\n\u003cp\u003eThe consumed ozone was determined by the difference in the values of gas not consumed by the water (white-B) and by the effluent (Ef) (2).\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{O}_{3co}{(mg\\:min}^{-1})=\\:{O}_{3res}\\left(B\\right)-{O}_{3res}\\left(Ef\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere:\u003c/p\u003e \u003cp\u003eO\u003csub\u003e3co\u003c/sub\u003e is consumed ozone (mg min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e);\u003c/p\u003e \u003cp\u003eO\u003csub\u003e3res\u003c/sub\u003e(B) is the residual ozone in the blank (mg min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e);\u003c/p\u003e \u003cp\u003eO\u003csub\u003e3res\u003c/sub\u003e(Ef) is the residual ozone in the effluent test (mg min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e).\u003c/p\u003e \u003cp\u003eThe experimental design was completely randomized (DIC), in a 7x2 factorial scheme, with 7 concentrations of coagulant (0, 50, 100, 150, 200, 250 and 300 mg L-1) and 2 times of contact with ozone (0 and 40 min), totaling 14 treatments, in triplicate.\u003c/p\u003e \u003cp\u003eThe results were submitted to analysis of variance (ANOVA), and when statistical difference was detected (p\u0026thinsp;\u0026le;\u0026thinsp;0.05), mean and regression tests were used.\u003c/p\u003e"},{"header":"3. RESULTS AND DISCUSSION","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Effect of Treatments\u003c/h2\u003e \u003cp\u003eThe analysis of variance revealed significant differences (p\u0026thinsp;\u0026le;\u0026thinsp;0.05) for color, turbidity, and COD concerning the sources of variation: coagulant dosages and ozonation time. Additionally, significant differences (p\u0026thinsp;\u0026le;\u0026thinsp;0.05) were observed for UV abs and BOD, specifically in relation to the source of variation, ozonation time. However, the interaction between the sources of variation did not yield any significant difference (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe pH value remained unchanged across all treatments, with a slight increase of approximately 11% at the end of the experiments compared to the initial values. Previous studies have shown that tannins do not affect the pH of the effluent as they do not deplete the alkalinity of the medium. Moreover, tannins exhibit a broad range of action within the pH scale, from 4.5 to 8.0 (Silveira et al. 2021).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of the analysis of variance for the evaluated parameters\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFactors\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eColor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTurbidity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eUV\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCOD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eBOD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDosage (Dose)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.8563\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.0000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.0000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.0280\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.2401\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOzonation time (OT)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.1598\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.0000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.0019\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.0013\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDose X OT\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.4653\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.2902\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.6353\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.6817\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.7744\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.8247\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\u003eValues less than or equal to 0.0500 classify the treatments as significant at the 5% probability level.\u003c/p\u003e \u003cp\u003eFor the UV abs parameter, a remarkable removal of 74% was observed when the sewage underwent ozone treatment. This increase in removal was significantly higher compared to the coagulation treatment alone (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eStudies by Lima and Abreu (2018) have indicated that the presence of humic and inorganic substances absorbs ultraviolet light. Additionally, Mena et al. (2020); Munyasamy et al. (2020) have observed that UV absorbance indicates the presence of aromatic and unsaturated substances (chromophores). Hence, the removal of UV abs demonstrates the ozone treatment's effectiveness in decomposing aromatic and unsaturated molecules.\u003c/p\u003e \u003cp\u003eSince color and UV abs are closely related to the presence of chromophoric substances in the liquid phase (Ghalebizade and Ayati 2016), any modifications in chromophoric compounds can cause noticeable interference in both the visible (color) (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) and ultraviolet (abs) ranges (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRegarding BOD, the coagulant treatment resulted in a removal of 36% (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Conversely, the utilization of ozone led to a significant increase in BOD removal, with an average value of 55%. While the achieved removal levels may not be as high as those for parameters such as color and turbidity, ozonation proves to be efficient in reducing the organic load in effluents, preparing them for further treatment. Furthermore, it can be inferred that ozone facilitates the degradation of organic matter, mineralizing more complex molecules and breaking them down into simpler forms that still contribute to BOD. Thus, ozone acts upon the effluent without generating substantial BOD removal.\u003c/p\u003e \u003cp\u003eSchons et al. (2018) obtained superior results (86%) in BOD removal compared to the findings presented in this study. The authors employed ozone in treating a combined raw landfill leachate and domestic sewage, with an ozonation time close to 30 hours and an ozone concentration approximately six times greater than that utilized in our research.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAbs UV and BOD removal as a function of ozonation time, %\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOT (min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUV abs.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBOD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e55\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 terms of apparent color, the utilization of ozonation resulted in an impressive removal rate of 86% (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). This significant efficiency in removing colloidal and suspended materials clearly demonstrates the effectiveness of ozonation. Moreover, visual observations during the ozonation process revealed noticeable changes in the effluent's color, transitioning from gray to white/transparent (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This color transformation aligns with previous findings reported by Silva et al. (2016).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAdditionally, Muniyasamy et al. (2020) propose that the reduction in color is linked to O\u003csup\u003e3\u003c/sup\u003e attacking the chromophoric carbon double bonds, resulting in the formation of \"bleached\" molecules like aliphatic acids and aldehydes, which are generally more biodegradable. This ozone-induced breakdown of double bonds generates simpler molecules, aligning with the BOD results obtained.\u003c/p\u003e \u003cp\u003eFurthermore, ozone exhibits potential for bleaching effluents, particularly in situations where reuse is a consideration.\u003c/p\u003e \u003cp\u003eAnalyzing the removal of color in relation to the coagulant dosage (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea), a certain level of stability in removal efficiency (~\u0026thinsp;80%) is observed when the dosage exceeds 75 mg/L. However, for coagulant dosages greater than 50 mg/L, removal rates above 70% were achieved.\u003c/p\u003e \u003cp\u003eThe outcomes for color removal align with the findings of Jawad et al. (2017); Silveira et al. (2021) when treating domestic sewage and surface water, respectively. These studies demonstrate the coagulant's remarkable efficiency in removing particulate matter and further underscore the potential of combining ozone with coagulation/flocculation processes.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRemoval of color, turbidity and BOD as a function of ozonation time, %\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOT (min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eColor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTurbidity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCOD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e58\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e71\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 terms of turbidity, an average removal of 87% was achieved when the effluent came into contact with ozone (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). However, even without the application of ozone gas, significant removal was observed. This can be attributed to the coagulant's ability to eliminate suspended solids.\u003c/p\u003e \u003cp\u003eThe turbidity removal values obtained in this study were higher than those reported by Camilo et al. (2019) when assessing the removal of physical attributes from sewage through ozonation.\u003c/p\u003e \u003cp\u003eThe reduction in turbidity when effluents are exposed to ozone is attributed to the ability of ozone to break down particles and organic compounds with greater mass, converting them into dissolved molecules (Miklos et al. 2018).\u003c/p\u003e \u003cp\u003eRegarding the range of coagulant dosages used for turbidity removal (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb), it was noted that a certain stabilization of removal occurred for dosages exceeding 150 mg/L. Oliveira (2016) achieved similar results using tannin in the dosage range of 200 to 250 mg/L at pH 7. Silveira et al. (2020) evaluated tannin coagulant at varying concentrations ranging from 261 mg/L to 1568 mg/L. Their experimental tests showed that the best results were obtained with a natural pH (without pH adjustment), achieving 100% turbidity removal in sanitary effluents. For this experiment, good removals were also observed in the dosage range of 50 mg/L.\u003c/p\u003e \u003cp\u003eBoth natural and artificial coagulants consist of large molecular chains with positive or negative charges, allowing them to adsorb particles in their vicinity (Zhao et al. 2019). Tannin-based coagulants are widely used for turbidity removal due to their ability to neutralize surface charges of suspended colloids, aiding in agglomeration and sedimentation (Silveira et al. 2021).\u003c/p\u003e \u003cp\u003eThe behavior of COD removal was similar to that of color and turbidity parameters, with a removal rate of 71% when the effluent was exposed to the oxidizing gas (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The primary treatment targeted the removal of particulate and colloidal COD, while ozonation primarily affected the dissolved COD portion.\u003c/p\u003e \u003cp\u003eHoffmann et al. (2020), studying the effect of ozonation in raw landfill leachate treatment, reported good COD removal at pH 7, a value very similar to the average found in this study (7.18).\u003c/p\u003e \u003cp\u003eLei and Li (2014), when applying ozone in sewage, suggested that a portion of the COD removal may be attributed to the stripping (mass exchange between liquid and gas) of organic gases. In other words, the chemical oxygen demand may have varied due to both ozone oxidation and mass transfer between the liquid (effluent) and gaseous (ozone) phases.\u003c/p\u003e \u003cp\u003eCOD was also influenced by coagulant dosages (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec), although it did not follow the same stabilization trend observed for color and turbidity. Dosages ranging from 50 to approximately 160 mg/L exhibited better removal rates (70% or more), while at other concentrations, removal rates above 50% were observed.\u003c/p\u003e \u003cp\u003eThe COD removal results obtained in this study were slightly higher than those reported by Silveira et al. (2020) when evaluating the potential application of physicochemical processes using tannin coagulant and advanced oxidative ozonation in the treatment of sanitary effluents. In their study, the authors achieved 48% COD removal at the optimal tannin concentration of 523 mg/L. Coagulants generate a larger volume of sludge compared to other treatment technologies, resulting in a higher concentration of organic matter in the generated sludge and effectively removing significant amounts of waste from the effluent (Ghalebizade and Ayati, 2016; Kamiwada et al. 2020).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWith the BOD and COD data, it was possible to estimate the biodegradability (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) as a function of the primary treatment and the combination of primary and ozone.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe results demonstrated variations in the BOD/COD ratio depending on the treatment employed. Coagulant dosages exceeding 250 mg/L for CF and 175 mg/L for CF\u0026thinsp;+\u0026thinsp;O\u003csup\u003e3\u003c/sup\u003e fell below the optimal range indicative of good biodegradability (\u0026gt;\u0026thinsp;0.5) (Scandelai et al. 2021). Nevertheless, the treatments still led to an improvement in the effluent's biodegradability compared to the raw effluent, which had a BOD/COD ratio of 0.30.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Consumed Ozone\u003c/h2\u003e \u003cp\u003eThe consumed ozone values exhibited a tendency to increase with higher coagulant dosages (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). It appears that the addition of the coagulant promotes ozone consumption without proportionally enhancing the removal efficiency of the evaluated parameters (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA plausible explanation for this behavior is that the ozone may react with the residual coagulant from the coagulation process. This hypothesis is supported by the drastic clarification observed in the effluent after ozonation. Ozone has the ability to react with a wide range of functional groups, leading to the breakdown of carbon-carbon double bonds and the formation of lower molecular weight by-products (Fonseca et al. 2017; Ikehata and Li, 2018; BEL\u0026Eacute; et al. 2021).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Residual Values\u003c/h2\u003e \u003cp\u003eThe applied treatment demonstrated high removal values for the analyzed parameters, particularly for color and COD. However, it is worth noting that turbidity and BOD are of greater significance, as they indicate the ability of the CF\u0026thinsp;+\u0026thinsp;O\u003csup\u003e3\u003c/sup\u003e combination to meet regulatory standards for discharge (Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe residual values of the evaluated parameters were generally lower for the ozone treatment, with the exception of pH. By combining coagulation (dosages above 200 mg/L) with ozone (40 minutes of treatment time), the effluent acquires characteristics suitable for release into water bodies, as demonstrated by BOD removal rates exceeding 60%.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResidual values obtained for the analyzed parameters of raw and treated effluents as a function of contact with ozone and doses of coagulant\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e0 minutes of \u003csub\u003eO3\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e40 minutes of \u003csub\u003eO3\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEph. gross\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEph. Treated\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eEph. gross\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEph. Treated\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e0 mg L\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH \u003csup\u003e(1)\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.6 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.2 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColor (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ) \u003csup\u003e(2)\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1698.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e744.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU) \u003csup\u003e(3)\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e104.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e65.1 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs. 254nm (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e337.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e291.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ) \u003csup\u003e(4)\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e156.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e138.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e50 mg L\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.7 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.1 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColor (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e808.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e265.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60.9 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28.2 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs. 254nm (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e196.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e162.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e110.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e94.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e100 mg L\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.1 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColor (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e760.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e221.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55.3 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e19.2 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs. 254nm (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e235.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e137.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e124.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e95.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e150 mg L\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColor (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e643.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e166.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.3 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.1 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs. 254nm (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e227.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e131.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e114.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e81.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e200 mg L\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.1 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColor (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e478.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e182.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24.7 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.9 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs. 254nm (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e237.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e148.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e131.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e65.1 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e250 mg L\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColor (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e626.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e156.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.7 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs. 254nm (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e376.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e173.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e141.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79.7 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e300 mg L\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.9 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.9 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColor (mg Pt Co L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e501.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1930.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e174.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTurbidity (NTU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24.0 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e13.9 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUV abs. 254nm (cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e271.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e655.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e175.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBOD (mg L \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e123.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e65.7 \u003csup\u003e*\u003c/sup\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\u003eCaption. Ideal ranges according to CONAMA resolutions 357/2005 and 430/2011 for disposal in class 2 rivers [(1) \u0026ndash; (5\u0026ndash;9); (2) \u0026ndash; (75 mg Pt Co L \u003csup\u003e-1\u003c/sup\u003e ); (3) \u0026ndash; (100 NTU); (4) \u0026ndash; (minimum removal of 60%)]. For UV abs. and COD there are no minimum values. Residuals marked with asterisks (*) highlight values where release standards were achieved after treatment.\u003c/p\u003e \u003cp\u003eSeveral studies have been conducted on the integration of ozone with other advanced oxidation processes (AOPs) and its combination with conventional treatments for polishing purposes (Ikehata and Li 2018; Hidayaturrahman and Lee 2019; Silveira et al. 2020; Sun et al. 2019; Li et al. 2022). The efficiency of biological treatments has been shown to increase when combined with the coagulation/flocculation\u0026thinsp;+\u0026thinsp;ozone\u0026thinsp;+\u0026thinsp;biological treatment sequence (Mella et al. 2018; Scandelai et al. 2021). Additionally, high BOD removals have been achieved by Silva and Daniel (2015) when using ozone followed by chlorine disinfection. Pastore et al. (2018) compared different treatments for landfill leachate and found that the most effective approach was the combination of biological treatment and ozonation, when considering the RBGSB (batch sequential granular biofilter) reactor along with other treatments such as hydrogen peroxide, ultraviolet and hydrogen peroxide, and ozonation.\u003c/p\u003e \u003cp\u003eThe results presented in this study, along with findings from other researchers, highlight the significant potential of ozonation in effluent treatment.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. CONCLUSIONS","content":"\u003cp\u003eThe combination of coagulation/flocculation and ozonation proves to be highly efficient in treating sanitary sewage effluents. Coagulation/flocculation and coagulation/flocculation\u0026thinsp;+\u0026thinsp;ozonation demonstrated remarkable removal rates for apparent color (\u0026gt;\u0026thinsp;80%), turbidity (~\u0026thinsp;87%), and COD (\u0026gt;\u0026thinsp;71%). However, the highest removal rates for UV abs. (74%) and BOD (55%) were achieved only when ozonation was applied.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAUTHOR CONTRIBUTIONS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri and Roselene Maria Schneider; Methodology: Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri and Roselene Maria Schneider; Formal analysis and investigation: Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri, Roselene Maria Schneider and Adriana Garcia do Amaral; Writing - original draft preparation: Matheus Caneles Batista Jorge; Writing - review and editing Matheus Caneles Batista Jorge, Milene Carvalho Bongiovani Roveri, Roselene Maria Schneider and Karoline Carvalho Dornelas; Supervision: Milene Carvalho Bongiovani Roveri, Roselene Maria Schneider, Adriana Garcia do Amaral and Karoline Carvalho Dornelas.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eACKNOWLEDGEMENTS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank the Institute of Agricultural and Environmental Sciences, Federal University of Mato Grosso (UFMT-Sinop), for the financial support.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e-Ethical Approval: Not applicable.\u003c/p\u003e\n\u003cp\u003e-Consent to Participate: Not applicable.\u003c/p\u003e\n\u003cp\u003e-Consent to Publish: Not applicable.\u003c/p\u003e\n\u003cp\u003e-Funding: No funding was received to assist with the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e-Competing Interests: All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAlmeida Junior RL (2006) Redu\u0026ccedil;\u0026atilde;o de cor do licor negro da ind\u0026uacute;stria de celulose de algod\u0026atilde;o com a utiliza\u0026ccedil;\u0026atilde;o de oz\u0026ocirc;nio em meio b\u0026aacute;sico. 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Frontiers of Environmental Science \u0026amp; Engineering 13(5):75. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11783-019-1159-7\u003c/span\u003e\u003c/span\u003e\n \u003c/li\u003e\n\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":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"brazilian-journal-of-chemical-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bjce","sideBox":"Learn more about [Brazilian Journal of Chemical Engineering](http://link.springer.com/journal/43153)","snPcode":"43153","submissionUrl":"https://www.editorialmanager.com/bjce/default2.aspx","title":"Brazilian Journal of Chemical Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Clarification, Physical-chemical, Polishment, Tertiary treatment","lastPublishedDoi":"10.21203/rs.3.rs-4870203/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4870203/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCoagulation/flocculation and ozonation are two treatment methods commonly used for effluents. Coagulation/flocculation destabilizes the charged particles in the medium, causing them to aggregate for subsequent separation through decantation or flotation. On the other hand, ozonation is an advanced oxidative treatment that can be employed for effluent polishing. This study aimed to evaluate the effectiveness of combining coagulation/flocculation and ozonation as an alternative treatment for raw sewage collected at the Curupy treatment station in Sinop, MT. The experiments were conducted in batches, involving seven doses of tannin-based coagulant (ranging from 0 to 300 mg L\u003csup\u003e-1\u003c/sup\u003e) with and without ozonation (for 40 minutes). Parameters such as pH, color, turbidity, UV absorbance (UV abs), chemical oxygen demand (COD), and biochemical oxygen demand (BOD) were measured before and after the treatments. The results demonstrated that the pH values remained relatively unaffected by the treatments. However, ozonation consistently led to superior removal rates compared to non-ozonation for color, turbidity, UV abs, COD, and BOD (with removal percentages of 86, 87, 74, 71, and 55% respectively, compared to 60%, 74, 49, 58, and 36% without ozonation. For color and turbidity, stabilization of removal rates occurred at coagulant dosages above 100-150 mg L\u003csup\u003e-1\u003c/sup\u003e, regardless of ozone contact. Overall, the employed treatments ensured that the sewage met the required conditions for discharge into bodies of water and also made it suitable for potential reuse, thanks to the significant clarification of the effluent. The treatments effectively removed suspended and colloidal solids from the sewage as well as dissolved compounds.\u003c/p\u003e","manuscriptTitle":"Raw Sewage Treatment by Coagulation/Flocculation and Ozonization","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-09-18 11:04:39","doi":"10.21203/rs.3.rs-4870203/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-08-21T15:12:03+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-08-20T16:13:34+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Brazilian Journal of Chemical Engineering","date":"2024-08-09T18:36:14+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-09T11:54:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"Brazilian Journal of Chemical Engineering","date":"2024-08-06T14:02:40+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"brazilian-journal-of-chemical-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bjce","sideBox":"Learn more about [Brazilian Journal of Chemical Engineering](http://link.springer.com/journal/43153)","snPcode":"43153","submissionUrl":"https://www.editorialmanager.com/bjce/default2.aspx","title":"Brazilian Journal of Chemical Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c07e2a6b-1a3c-49bd-b95f-083d87acc07e","owner":[],"postedDate":"September 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-12-16T16:01:58+00:00","versionOfRecord":{"articleIdentity":"rs-4870203","link":"https://doi.org/10.1007/s43153-024-00525-0","journal":{"identity":"brazilian-journal-of-chemical-engineering","isVorOnly":false,"title":"Brazilian Journal of Chemical Engineering"},"publishedOn":"2024-12-14 15:57:44","publishedOnDateReadable":"December 14th, 2024"},"versionCreatedAt":"2024-09-18 11:04:39","video":"","vorDoi":"10.1007/s43153-024-00525-0","vorDoiUrl":"https://doi.org/10.1007/s43153-024-00525-0","workflowStages":[]},"version":"v1","identity":"rs-4870203","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4870203","identity":"rs-4870203","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}