A comprehensive study on nutrient removal from domestic wastewater by integrated anoxic and fixed-bed membrane bioreactors

A comprehensive study on nutrient removal from domestic wastewater by integrated anoxic and fixed-bed membrane bioreactors | 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 A comprehensive study on nutrient removal from domestic wastewater by integrated anoxic and fixed-bed membrane bioreactors Mahbubeh Ezzati Shourgoli, Amir Hessam Hassani, Amirhossein Javid, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7847046/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract A comprehensive study was developed to investigate the roles of combined anoxic and fixed bed MBR (FBMBR) in nutrient removal from the municipal wastewater. The performance of anoxic + FBMBR in different organic loading rate (OLR) (0.58, 2.15 and 2.45 kg COD/m 3 .day) in terms of COD, BOD, total nitrogen (TN) and total phosphorus (TP) with study period of 180 days. The results indicated that the highest removal efficiency for COD (93.92%) was obtained in ORL equal to 2.15 kgCOD/m 3 d (93.92%). However, the COD removal efficiency for OLR equal to 2.45 kgCOD/m 3 d was promising (90.94%). In case of nutrients, the highest removal efficiency for TN and TP within the study period were 94.98% and 57%, respectively and meet the standards for discharge to the environment. Therefore, the combined anoxic and FBMBR is a promising technology for efficient removal of nutrients from the municipal wastewater with high concentration levels of nutrients. Membrane Reactor Biological Reactor Nitrogen Phosphorous Anoxic Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction The explosive human population growth, anthropogenic and industrial activities are responsible for huge production of wastewater containing toxic pollutants, damaging the human health and environments [ 1 , 2 ]. The discharge of nutrient-rich wastewater, particularly containing high levels of nitrites, nitrates, and phosphorus, into aquatic environments can trigger eutrophication and pose serious health risks, such as blue baby syndrome in infants [ 3 ]. Eutrophication exerts cascading effects on aquatic ecosystems, beginning with zooplankton and extending throughout the food web. Additionally, nitrogen oxides and ammonia inputs alter water pH and dissolved oxygen dynamics, aggravating ecological imbalance [ 4 ][ 5 ]. Ammonia represents one of the principal contaminants in wastewater, largely originating from human activities such as municipal effluent release, fertilizer-laden agricultural runoff, and a wide spectrum of industrial processes including the production of pharmaceuticals, plastics, explosives, textiles, pesticides, dyes, and other chemicals [ 6 ]. Ammonia and nitrate are highly toxic to organisms in the marine world and pose a variety of health risk such as suffocation, irritation of throat and eyes, if present at high concentration in the drinking water [ 7 ]. However, the ever strict regulation on wastewater discharge into environment make authorities and researchers to find a promising method in order to minimize the nutrients discharge into environment [ 8 ]. Although different physical and chemical methods including ion-exchange, reverse osmosis and dechlorination have been employed to remove the ammonia from the wastewater, biological treatment process and microbial methods are known as most traditional and cost-effective for nitrogen and phosphorous removal from the wastewater [ 9 ]. Traditional microbial method focused on the successive nitrification and denitrification processes; Nitrifying bacteria convert the ammonia to nitrous and nitric oxides and consequently denitrifying bacteria transform the nitrogen oxides to dinitrogen [ 1 ]. Nitrification process demands a considerable supply of oxygen, while, the denitrification occurs in the anoxic condition and requires the external organic carbon as the electron donor. Overall, the basic problem imposed for conventional nitrification process is the much slower growth of nitrifying bacteria compared to heterotrophic bacteria [ 10 ]. In addition, other significant factors including settling limitations for levels of biomass (suspended solids), requirements for specific configurations and not favor of activated sludge for simultaneous nitrification/denitrification (SNdN) [ 11 ][ 12 ]. These requirements and considerations make authorities and researchers to overcome these problems and find a promising technology. Over the recent years, membrane bioreactor (MBR) technology has gained great attention for efficient treatment of wastewater treatment and reuse of nutrients [ 13 ]. Membrane bioreactors (MBRs) are capable of generating effluents of superior quality while ensuring compliance with stringent regulatory standards for wastewater discharge [ 14 ]. The effective elimination of organic matter, micronutrients, and persistent compounds remains a critical challenge in both domestic and pharmaceutical wastewater management. Membrane bioreactor (MBR) technology offers a viable treatment solution, distinguished from conventional methods by its ability to sustain exceptionally high microbial concentrations (exceeding 20,000 mg/L) within a compact processing unit [ 15 ]. Moreover, MBRs offer additional benefits, including resilience to elevated organic loading, the production of highly disinfected effluents, and a notable reduction in sludge generation [ 16 ]. Over the recent years, many studies have focused on the efficient removal of nutrients from the wastewater via the modified MBR process. For instance, Rouzbeh Abbassi and et al. (2014) surveyed the possibility of MBR in simultaneous nitrification-anammox-denitrification (SNAD) for removal of total nitrogen (TN) in different periodic aeration cycles [ 17 ]. According to the authors, the coexistence of anammox biomass with nitrifying and denitrifying communities in MBR systems enabled the removal of 98% of total nitrogen (TN) and 83% of total organic carbon (TOC) under operational conditions involving one hour of aeration within a four-hour cycle [ 17 ]. In addition, M. Sarioglu and et al. (2009) surveyed the simultaneous nitrification and denitrification processes in MBR operated without anoxic reactor in order to efficient removal of Nitrogen from the wastewater [ 11 ]. Findings revealed that an MBR operating with solid concentrations between 17,500 and 21,000 mg/L at 25°C, and maintaining a dissolved oxygen level of about 1.8 mg O₂/L, achieved nitrogen removal efficiencies of 85–95% when treating typical domestic wastewater [ 11 ]. This study was designed to evaluate the nutrient (N and P) removal performance of integrated anoxic and FBMBR reactors operated under varying loading rates and treatment scenarios 2. Materials and methods This pilot-scale experimental study, utilizing actual municipal wastewater, investigated the performance of a continuous-mode MBR in reducing organic pollutants (BOD, COD) and nutrients (TP, TN) over 180 days, under two operational regimes with varying organic loading rates. Furthermore, the four operational setups were comparatively assessed to determine the system’s efficiency in eliminating organic matter and nutrients under both high and low aeration regimes 2.1. Wastewater sampling and characterization Table 1 provides a summary of the physico-chemical properties of the real domestic wastewater samples analyzed throughout the study period Table 1 Physico-chemical characteristics of raw domestic wastewater used in the pilot study period. Parameter Mean Min. Max. BOD 5 (mg/L) 255 235 283 COD (mg/L) 504 451 561 NH 4 (mg/L) 37 31 43 TKN (mg/L) 62 56 69 TP (mg/L) 6.0 5.6 6.9 2.2. Pilot configuration Figure 1 illustrates the schematic layout of the anoxic and MBR pilot system employed in this study. The setup, designed as an FBMBR with packing media, was constructed from Plexiglas and aimed at nutrient removal from domestic wastewater. The pilot consisted of two identical chambers, each with a volume of 140 L (dimensions: 40 cm length × 35 cm width × 100 cm height) and a wall thickness of 10 mm. In this study, domestic wastewater was initially collected in a 500 L feed tank over the course of a day before being directed to the anoxic reactor. Subsequently, a suction pump with a maximum capacity of 30 L/h was employed to transfer the effluent into the FBMBR unit. The output pressure of membrane was also measured by the pressure gauges. The subsurface aeration function in the FBMBR reactor was provided by the placement of blowers and diffusers at bottom of the pilots. The pilot was operated during 180 days at a sewage temperature of about 25 ° C. The acclimation process of pilot was prepared by gradually feeding of sludge at 25, 50 and 100% volume loading. The acclimation process of FBMBR was evaluated by determination the removal efficiency of organic and nutrient within 2 months. 2.4. MBR operational performances In this study, the efficiency and performance of MBR for removal of organic and nutrient were investigated in different scenarios and increasing trend organic loading rate (OLR) based on COD (2.15 and 2.45 KgCOD/day). The corresponding hydrolytic retention time (HRT) for different OLR were 21.4 and 17.4 h, respectively. In addition, the aeration conditions were considered to be less than 1 mg / L in order to provide the anoxic condition in the treatment system. Table 2 shows the operational specifications of pilot scenarios, taking into account aeration, organic loading, and HRT. Table 2 Operational condition of wastewater treatment Pilot Period (days) Scenario HRT (h) OLR (kgCOD/m 3 d) DO (mg/L) MLVSS (mg/L) 1–60 Start-up 21.4 0.58 > 4 652 61–123 S1 17.4 2.15 > 4 2420 124–180 S2 9.1 2.45 > 4 3100 2.5. Analytical Analysis The evaluation of operational parameters and nutrient removal efficiency in the treatment system was carried out by measuring BOD₅, COD, total nitrogen (TN), and total phosphorus (TP) at the inlet and outlet of the FBMBR pilot, following the analytical procedures summarized in Table 3 and in accordance with standard methods for water and wastewater analysis [ 18 ]. The COD parameter was measured by the Spectrophotometer (HACH) model DR5000 and BOD meter model BODTrakTM was used to measure the BOD 5 parameter. Additionally, the nutrient removal efficiency based on NO3- and PO 4 3− were evaluated by measuring the concentrations of these parameters from the influent and effluent samples once a day during the study period and different scenarios. Of note, the NO 3 − and PO 4 3− concentrations were analyzed as per the procedures outlined in the standard methods for water and wastewater examination [ 18 ]. Table 3 Standard test method for qualitative parameters Parameter Devices Procedure BOD 5 BODTrakTM APHA (2005)-5210 B COD HACH DR5000 APHA (2005)-5220 D NO 3 HACH DR5000 APHA (2005)-4500 NO 3 PO 4 HACH DR5000 APHA (2005)-4500 P 3. Results and Discussion 3.1. Operational performance of MBR and FBMBR 3.1.1. COD removal efficiency Figure 2 illustrates the COD trends for raw wastewater, FBMBR effluent, and corresponding COD removal efficiencies under different OLR scenarios. As depicted, the COD of the influent wastewater entering the pilot system ranged between 451 and 561 mg/L, with only minor fluctuations observed between the anoxic reactor and the FBMBR unit. Throughout the 180-day experimental period, the FBMBR produced effluent with an average COD concentration of 38 mg/L, ranging from a minimum of 17 mg/L to a maximum of 47 mg/L. Furthermore, the temporal pattern of COD removal efficiency over the study duration is depicted in Fig. 2 . Overall, the high and acceptable COD removal efficiency were observed in two different scenarios of operation. As shown in Fig. 2 , the average COD removal efficiency in scenario 1 and OLR equal to 2.15 kgCOD/m 3 d (93.92%) was higher than that for scenario 2 and OLR of 2.45 kgCOD/m 3 d (90.94%)(p-value < 0.008). C. Visvanathan and et al. (2008) investigated the Hydrogenotrophic denitrification of synthetic aquaculture wastewater using membrane bioreactor. The authors reported that in MBR reactors are able to remove 80–90% COD equal to 50 mg/L created with addition the fish food, excreta and glucose with operational condition of HRT of 2–9 h [ 2 ]. These results are comparable with the present study. L. Rodríguez-Hernández and et al. (2014) surveyed the COD removal efficiency on the fixed bed hybrid membrane bioreactor by adding the biofilm and support media. The results indicated that the fixed bed MBR are able to better remove COD (84%) compared to that for conventional MBR (80%); the COD of effluent from fixed bed MBR and conventional MBR were 54 and 65 mg/L, respectively [ 19 ]. The high growth of biofilm on the packing bed of FBMR is the most possible reason for high COD removal efficiency [ 20 ]. 3.1.2. BOD removal efficiency The BOD variation for wastewater, the effluent of FBMR and BOD removal efficiency for different OLR scenario within the study period are illustrated in Fig. 3 . A shown in Fig. 3 the initial BOD of the wastewater entering the reactor and treatment system ranged from 235 to 283 mg/L, with only minor fluctuations observed between the anoxic reactor and the FBMBR unit. Over the 180-day study period, the effluent from the FBMBR exhibited an average BOD of 22 mg/L, with values ranging from a minimum of 14 mg/L to a maximum of 25 mg/L. Additionally, the temporal pattern of BOD removal efficiency throughout the study is presented in Fig. 3 . Generally, the high and acceptable BOD removal efficiency were achieved in two different scenarios of operation. As shown in Fig. 3 , the average BOD removal efficiency in scenario 1 and OLR equal to 2.15 kgCOD/m 3 d (91.78%) was higher than that for scenario 2 and OLR of 2.45 kgCOD/m 3 d (85.73%) (p-value < 0.008). Palmarin J and et al. (2019) surveyed the treatment performance of a hybrid MBR equipped with biocarrier for greywater reclamation [ 21 ]. The initial BOD for the graywater was 150 mg/L. The results indicated that the hybrid MBR are able to remove BOD until 97%; the BOD in the effluents were 4 ± 2 mg BOD/L. L. Rodríguez-Hernández and et al. (2014) investigated treatment performance of municipal wastewater with initial BOD equal to 39 mg/ L using the FBMBR [ 22 ]. The result indicated that the FBMBR with HRT = 24 h are able to remove BOD until 98%. The main possible reason for the differences of these values reported here and the present study are attributed to low initial BOD of wastewater. 3.1.3. TKN and NH 4 + removal efficiency Figure 4 (a- b) illustrate the TKN and NH 4 + variation in the raw wastewater and the effluent from the FBMBR and in addition the removal efficiency based on the different OLR scenario. As shown in Fig. 4 (a) , the initial TKN of wastewater fed into reactor and treatment process were between 59 and 69 mg/L with a little variation in wastewater fed into anoxic container and FBMBR. The average TKN in the effluent from the FBMBR and TKN removal efficiency were estimated to be 16 mg/L (min: 11 mg/L, max: 22 mg/L) and 74.12% (min: 62.07%, max: 81.67%), respectively. Furthermore, the NH 4 + in effluent from FBMBR and NH 4 + removal efficiency is presented in Fig. 4 (b). As shown in Fig. 4 (b) , the average NH 4 + in the effluent from the FBMBR and NH 4 + removal efficiency were estimated to be 2.81 mg/L (min: 2.16 mg/L, max: 3.05 mg/L) and 92.32% (min: 90.35%, max: 94.98%), respectively. L. Rodríguez-Hernández and et al. (2014) surveyed the removal efficiency of TN and NH 4 + in a hybrid membrane bioreactor (HMBR), developed by addition the biofilm support media. The results indicated that the TKN and NH 4 + removal efficiency were 75% and 95%, respectively with initial concentration levels of 39 mg/L and 0.4 mg/L, respectively [ 19 ]. These values and removal efficiency are comparable with the results presented here. In addition, Hee Seok Kim (2008) investigated the enhanced nitrogen removal efficiency from the piggery wastewater by MBR combined with nitrification process. The results indicated that 68% of initial ammonia were removed by this process (initial NH 4 + in the wastewater: 2560 mg/L) [ 23 ]. The presence of attached biofilm on the fixed bed MBR prevention the oxygen diffusion into biofilm and the presence of aeration intensity (high ambient DO) in the reactor with small size flock are the most possible reason for TN and NH 4 + removal due to nitrification and denitrification process [ 23 ]. 3.1.3. TP removal efficiency The TP removal efficiency variation from the treatment process equipped with anoxic and FBMBR are illustrated in Fig. 5 . As can be seen from the Fig. 5 , the highest TP removal efficiency (66.03%) was achieved in the lower OLR; the average TP removal efficiency within the study period was 57%. The variation of concentration levels of TP in the effluent of FBMBR are illustrated in Fig. 5 . The average TP concentration level in the effluent of FBMBR were 2.6 mg/L (min: 2.21 mg/L and max: 2.81 mg/L). L. Rodríguez-Hernández and et al. (2014) Reported that a hybrid membrane bioreactor (HMBR) with biofilm support media are able to remove the TP by 42%; the concentration levels of PO 4 3− in the effluent of HMBR was estimated to be 2.0 ± 0.3 mg/ L, which is similar to the results presented here [ 19 ]. The effective removal of total phosphorus (TP) in the FBMBR system is primarily attributed to the growth of biomass, particularly phosphorus-accumulating organisms (PAOs) on the biofilm, along with the presence of anoxic and anaerobic zones within the support media [ 24 ]. 4. Conclusion A comprehensive study was designed to survey the treatment efficiency of combined anoxic and fixed bed MBR (FBMBR) in nutrient removal from the municipal wastewater. Here, the comprehensive study was developed to survey the roles of combined anoxic and FBMBR in treatment efficiency of municipal wastewater containing high concentration levels of nutrients. In addition, the roles of different OLD on the operational parameters including COD, BOD, TN and TP were examined. The results from the present study indicated that this combined biological method led to efficient removal of pollutants and nutrients from the wastewater. The highest removal efficiency for TN (94.98%) and TP (57%) were achieved within the study period, this combined method (anoxic + FBMBR) is a feasible and promising technology to treat the municipal wastewater containing high levels of nutrients. Declarations Acknowledgement The present study was funded by West Tehran branch, Islamic Azad University, Tehran, Iran. Author Contributions: Mahbubeh Ezzati Shourgoli : Methodology, Investigation, Writing. Amir Hessam Hassani: Conceptualization, Supervision, Editting. Amirhossein Javid : Methodology, investigation. Roya Mafigholami and Rouhallah Mahmoudkhani: Investigation, Analysis. Funding This research did not receive any funding. Data availability The datasets generated and analyzed during the current study were available from the corresponding author on reasonable request. Ethics approval and consent to participate: Not applicable. Consent for publication: All authors have read and agreed to the published version of the manuscript. Clinical trial declarations: Not applicable . Competing interests: The authors declare no competing interests. References Manasa RL, Mehta A. Current perspectives of anoxic ammonia removal and blending of partial nitrifying and denitrifying bacteria for ammonia reduction in wastewater treatment. J Water Process Eng. 2021;41:102085. https://doi.org/10.1016/j.jwpe.2021.102085 . Visvanathan C, Hung NQ, Jegatheesan V. Hydrogenotrophic denitrification of synthetic aquaculture wastewater using membrane bioreactor. Process Biochem. 2008;43:673–82. https://doi.org/10.1016/j.procbio.2008.02.007 . Bartlett R, Mortimer RJG, Morris K. Anoxic nitrification: evidence from Humber Estuary sediments (UK). Chem Geol. 2008;250:29–39. Morris S, Garcia-Cabellos G, Ryan D, Enright D, Enright A-M. Low-cost physicochemical treatment for removal of ammonia, phosphate and nitrate contaminants from landfill leachate. J Environ Sci Heal Part A. 2019;54:1233–44. Fu Q, Zheng B, Zhao X, Wang L, Liu C. Ammonia pollution characteristics of centralized drinking water sources in China. J Environ Sci. 2012;24:1739–43. Yao J, Mei Y, Xia G, Lu Y, Xu D, Sun N, Wang J, Chen J. Process optimization of electrochemical oxidation of ammonia to nitrogen for actual dyeing wastewater treatment. Int J Environ Res Public Health. 2019;16:2931. Shin JH, Sang BI, Chung YC, kyoo Choung Y. A novel CSTR-type of hollow fiber membrane biofilm reactor for consecutive nitrification and denitrification. Desalination. 2008;221:526–33. https://doi.org/10.1016/j.desal.2007.01.113 . Jegatheesan V, Zeng C, Shu L, Manicom C, Steicke C. Technological advances in aquaculture farms for minimal effluent discharge to oceans. J Clean Prod. 2007;15:1535–44. Atkins PF Jr, Scherger DA, Barnes RA, Evans FL. III, Ammonia removal by physical-chemical treatment. J (Water Pollut Control Fed. (1973) 2372–88. Walter B, Haase C, Räbiger N. Combined nitrification/denitrification in a membrane reactor. Water Res. 2005;39:2781–8. https://doi.org/10.1016/j.watres.2005.04.027 . Sarioglu M, Insel G, Artan N, Orhon D. Model evaluation of simultaneous nitrification and denitrification in a membrane bioreactor operated without an anoxic reactor. J Memb Sci. 2009;337:17–27. https://doi.org/10.1016/j.memsci.2009.03.015 . Insel G. Effects of design and aeration control parameters on simultaneous nitrification and denitrification (SNdN) performance for activated sludge process. Environ Eng Sci. 2007;24:675–86. Rahman TU, Roy H, Islam MR, Tahmid M, Fariha A, Mazumder A, Tasnim N, Pervez MN, Cai Y, Naddeo V. The advancement in membrane bioreactor (MBR) technology toward sustainable industrial wastewater management. Membr (Basel). 2023;13:181. Mannina G, Alliet M, Brepols C, Comas J, Harmand J, Heran M, Kalboussi N, Makinia J, Robles Á, Rebouças TF. Integrated membrane bioreactors modelling: A review on new comprehensive modelling framework. Bioresour Technol. 2021;329:124828. Iorhemen OT, Hamza RA, Tay JH. Membrane bioreactor (MBR) technology for wastewater treatment and reclamation: membrane fouling. Membr (Basel). 2016;6:33. Deng L, Guo W, Ngo HH, Wang XC, Hu Y, Chen R, Cheng D, Guo S, Cao Y. Application of a specific membrane fouling control enhancer in membrane bioreactor for real municipal wastewater treatment: sludge characteristics and microbial community. Bioresour Technol. 2020;312:123612. Abbassi R, Yadav AK, Huang S, Jaffé PR. Laboratory study of nitrification, denitrification and anammox processes in membrane bioreactors considering periodic aeration. J Environ Manage. 2014;142:53–9. https://doi.org/10.1016/j.jenvman.2014.03.013 . W. APHA, AWWA. Standard Methods for examination of water and wastewater, 2017. Rodríguez-Hernández L, Esteban-García AL, Tejero I. Comparison between a fixed bed hybrid membrane bioreactor and a conventional membrane bioreactor for municipal wastewater treatment: A pilot-scale study. Bioresour Technol. 2014;152:212–9. https://doi.org/10.1016/j.biortech.2013.10.081 . Arya V, Philip L, Bhallamudi SM. Performance of suspended and attached growth bioreactors for the removal of cationic and anionic pharmaceuticals. Chem Eng J. 2016;284:1295–307. Palmarin MJ, Young S. Comparison of the treatment performance of a hybrid and conventional membrane bioreactor for greywater reclamation. J Water Process Eng. 2019;28:54–9. https://doi.org/10.1016/j.jwpe.2018.12.012 . Fathali D, Rashidi Mehrabadi A, Mirabi M, Alimohammadi M. Investigation on nitrogen removal performance of an enhanced post-anoxic membrane bioreactor using disintegrated sludge as a carbon source: An experimental study. J Environ Chem Eng. 2019;7:103445. https://doi.org/10.1016/j.jece.2019.103445 . Kim HS, Choung YK, Ahn S, Oh HS. Enhancing nitrogen removal of piggery wastewater by membrane bioreactor combined with nitrification reactor. Desalination. 2008;223:194–204. https://doi.org/10.1016/j.desal.2006.12.021 . Liu Q, Wang XC, Liu Y, Yuan H, Du Y. Performance of a hybrid membrane bioreactor in municipal wastewater treatment. Desalination. 2010;258:143–7. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. 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12:49:29","extension":"html","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":90160,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7847046/v1/1bee6b1663097c974ae44aa8.html"},{"id":95203140,"identity":"5cb4787b-3e51-4938-94a2-88fb4fdb1405","added_by":"auto","created_at":"2025-11-05 12:49:28","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":159835,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic diagram of integrated anoxic and MBR with packing media.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7847046/v1/fec399318a0c81ccfba4193a.jpg"},{"id":95203142,"identity":"625478a1-10fb-4904-b9c2-ba7733dcc8fa","added_by":"auto","created_at":"2025-11-05 12:49:28","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":254545,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe COD removal efficiency in FBMR.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7847046/v1/fbd3ac1bc10815f6a4498b8e.jpeg"},{"id":95203150,"identity":"61755c5a-aa75-41eb-9deb-9654f0590325","added_by":"auto","created_at":"2025-11-05 12:49:28","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":239371,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe BOD removal efficiency in FBMR.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7847046/v1/c68f080164be6aafa19e410b.jpeg"},{"id":95228853,"identity":"d003ec96-7ece-46b0-a632-0bbce80a9022","added_by":"auto","created_at":"2025-11-05 16:34:12","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":230072,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe TN (a) and NH\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e (b) removal efficiency in FBMR.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7847046/v1/ca9fdda7cab32d8376564398.jpg"},{"id":95228997,"identity":"b80d6435-a5f4-4bfe-b743-c64d9d3f5f7c","added_by":"auto","created_at":"2025-11-05 16:34:20","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":187190,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe TP removal efficiency in FBMR.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7847046/v1/b07bd19554011d0505f3b554.jpeg"},{"id":95312676,"identity":"02e9b5ed-c9a0-4719-9c03-494a3ae95132","added_by":"auto","created_at":"2025-11-06 15:50:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1868629,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7847046/v1/b87ce4f7-1a75-473e-8c49-9fec1bd03fc4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"A comprehensive study on nutrient removal from domestic wastewater by integrated anoxic and fixed-bed membrane bioreactors","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe explosive human population growth, anthropogenic and industrial activities are responsible for huge production of wastewater containing toxic pollutants, damaging the human health and environments [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The discharge of nutrient-rich wastewater, particularly containing high levels of nitrites, nitrates, and phosphorus, into aquatic environments can trigger eutrophication and pose serious health risks, such as blue baby syndrome in infants [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Eutrophication exerts cascading effects on aquatic ecosystems, beginning with zooplankton and extending throughout the food web. Additionally, nitrogen oxides and ammonia inputs alter water pH and dissolved oxygen dynamics, aggravating ecological imbalance [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e][\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Ammonia represents one of the principal contaminants in wastewater, largely originating from human activities such as municipal effluent release, fertilizer-laden agricultural runoff, and a wide spectrum of industrial processes including the production of pharmaceuticals, plastics, explosives, textiles, pesticides, dyes, and other chemicals [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Ammonia and nitrate are highly toxic to organisms in the marine world and pose a variety of health risk such as suffocation, irritation of throat and eyes, if present at high concentration in the drinking water [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, the ever strict regulation on wastewater discharge into environment make authorities and researchers to find a promising method in order to minimize the nutrients discharge into environment [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Although different physical and chemical methods including ion-exchange, reverse osmosis and dechlorination have been employed to remove the ammonia from the wastewater, biological treatment process and microbial methods are known as most traditional and cost-effective for nitrogen and phosphorous removal from the wastewater [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Traditional microbial method focused on the successive nitrification and denitrification processes; Nitrifying bacteria convert the ammonia to nitrous and nitric oxides and consequently denitrifying bacteria transform the nitrogen oxides to dinitrogen [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Nitrification process demands a considerable supply of oxygen, while, the denitrification occurs in the anoxic condition and requires the external organic carbon as the electron donor. Overall, the basic problem imposed for conventional nitrification process is the much slower growth of nitrifying bacteria compared to heterotrophic bacteria [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In addition, other significant factors including settling limitations for levels of biomass (suspended solids), requirements for specific configurations and not favor of activated sludge for simultaneous nitrification/denitrification (SNdN) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e][\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. These requirements and considerations make authorities and researchers to overcome these problems and find a promising technology. Over the recent years, membrane bioreactor (MBR) technology has gained great attention for efficient treatment of wastewater treatment and reuse of nutrients [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Membrane bioreactors (MBRs) are capable of generating effluents of superior quality while ensuring compliance with stringent regulatory standards for wastewater discharge [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The effective elimination of organic matter, micronutrients, and persistent compounds remains a critical challenge in both domestic and pharmaceutical wastewater management. Membrane bioreactor (MBR) technology offers a viable treatment solution, distinguished from conventional methods by its ability to sustain exceptionally high microbial concentrations (exceeding 20,000 mg/L) within a compact processing unit [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Moreover, MBRs offer additional benefits, including resilience to elevated organic loading, the production of highly disinfected effluents, and a notable reduction in sludge generation [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Over the recent years, many studies have focused on the efficient removal of nutrients from the wastewater via the modified MBR process. For instance, Rouzbeh Abbassi and et al. (2014) surveyed the possibility of MBR in simultaneous nitrification-anammox-denitrification (SNAD) for removal of total nitrogen (TN) in different periodic aeration cycles [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. According to the authors, the coexistence of anammox biomass with nitrifying and denitrifying communities in MBR systems enabled the removal of 98% of total nitrogen (TN) and 83% of total organic carbon (TOC) under operational conditions involving one hour of aeration within a four-hour cycle [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In addition, M. Sarioglu and et al. (2009) surveyed the simultaneous nitrification and denitrification processes in MBR operated without anoxic reactor in order to efficient removal of Nitrogen from the wastewater [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Findings revealed that an MBR operating with solid concentrations between 17,500 and 21,000 mg/L at 25\u0026deg;C, and maintaining a dissolved oxygen level of about 1.8 mg O₂/L, achieved nitrogen removal efficiencies of 85\u0026ndash;95% when treating typical domestic wastewater [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. This study was designed to evaluate the nutrient (N and P) removal performance of integrated anoxic and FBMBR reactors operated under varying loading rates and treatment scenarios\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cp\u003eThis pilot-scale experimental study, utilizing actual municipal wastewater, investigated the performance of a continuous-mode MBR in reducing organic pollutants (BOD, COD) and nutrients (TP, TN) over 180 days, under two operational regimes with varying organic loading rates. Furthermore, the four operational setups were comparatively assessed to determine the system\u0026rsquo;s efficiency in eliminating organic matter and nutrients under both high and low aeration regimes\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Wastewater sampling and characterization\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e provides a summary of the physico-chemical properties of the real domestic wastewater samples analyzed throughout the study period\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\u003ePhysico-chemical characteristics of raw domestic wastewater used in the pilot study period.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMin.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMax.\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBOD\u003csub\u003e5\u003c/sub\u003e (mg/L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e255\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e235\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e283\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCOD (mg/L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e504\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e451\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e561\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNH\u003csub\u003e4\u003c/sub\u003e (mg/L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e43\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTKN (mg/L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e69\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTP (mg/L)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.9\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=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Pilot configuration\u003c/h2\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates the schematic layout of the anoxic and MBR pilot system employed in this study. The setup, designed as an FBMBR with packing media, was constructed from Plexiglas and aimed at nutrient removal from domestic wastewater. The pilot consisted of two identical chambers, each with a volume of 140 L (dimensions: 40 cm length \u0026times; 35 cm width \u0026times; 100 cm height) and a wall thickness of 10 mm. In this study, domestic wastewater was initially collected in a 500 L feed tank over the course of a day before being directed to the anoxic reactor. Subsequently, a suction pump with a maximum capacity of 30 L/h was employed to transfer the effluent into the FBMBR unit.\u003c/p\u003e\u003cp\u003eThe output pressure of membrane was also measured by the pressure gauges. The subsurface aeration function in the FBMBR reactor was provided by the placement of blowers and diffusers at bottom of the pilots. The pilot was operated during 180 days at a sewage temperature of about 25 \u0026deg; C. The acclimation process of pilot was prepared by gradually feeding of sludge at 25, 50 and 100% volume loading. The acclimation process of FBMBR was evaluated by determination the removal efficiency of organic and nutrient within 2 months.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.4. MBR operational performances\u003c/h2\u003e\u003cp\u003eIn this study, the efficiency and performance of MBR for removal of organic and nutrient were investigated in different scenarios and increasing trend organic loading rate (OLR) based on COD (2.15 and 2.45 KgCOD/day). The corresponding hydrolytic retention time (HRT) for different OLR were 21.4 and 17.4 h, respectively. In addition, the aeration conditions were considered to be less than 1 mg / L in order to provide the anoxic condition in the treatment system. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the operational specifications of pilot scenarios, taking into account aeration, organic loading, and HRT.\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\u003eOperational condition of wastewater treatment Pilot\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\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=\"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=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePeriod (days)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eScenario\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eHRT (h)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOLR\u003c/p\u003e\u003cp\u003e(kgCOD/m\u003csup\u003e3\u003c/sup\u003ed)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eDO\u003c/p\u003e\u003cp\u003e(mg/L)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMLVSS (mg/L)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u0026ndash;60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eStart-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e21.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e652\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e61\u0026ndash;123\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eS1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e17.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2420\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e124\u0026ndash;180\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eS2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e9.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3100\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=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Analytical Analysis\u003c/h2\u003e\u003cp\u003eThe evaluation of operational parameters and nutrient removal efficiency in the treatment system was carried out by measuring BOD₅, COD, total nitrogen (TN), and total phosphorus (TP) at the inlet and outlet of the FBMBR pilot, following the analytical procedures summarized in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and in accordance with standard methods for water and wastewater analysis [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The COD parameter was measured by the Spectrophotometer (HACH) model DR5000 and BOD meter model BODTrakTM was used to measure the BOD\u003csub\u003e5\u003c/sub\u003e parameter. Additionally, the nutrient removal efficiency based on NO3- and PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e were evaluated by measuring the concentrations of these parameters from the influent and effluent samples once a day during the study period and different scenarios. Of note, the NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e and PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e concentrations were analyzed as per the procedures outlined in the standard methods for water and wastewater examination [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eStandard test method for qualitative parameters\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\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDevices\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eProcedure\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBOD\u003csub\u003e5\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBODTrakTM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAPHA (2005)-5210 B\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\u003eHACH DR5000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAPHA (2005)-5220 D\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eHACH DR5000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAPHA (2005)-4500 NO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eHACH DR5000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAPHA (2005)-4500 P\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"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Operational performance of MBR and FBMBR\u003c/h2\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e3.1.1. COD removal efficiency\u003c/h2\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the COD trends for raw wastewater, FBMBR effluent, and corresponding COD removal efficiencies under different OLR scenarios. As depicted, the COD of the influent wastewater entering the pilot system ranged between 451 and 561 mg/L, with only minor fluctuations observed between the anoxic reactor and the FBMBR unit. Throughout the 180-day experimental period, the FBMBR produced effluent with an average COD concentration of 38 mg/L, ranging from a minimum of 17 mg/L to a maximum of 47 mg/L. Furthermore, the temporal pattern of COD removal efficiency over the study duration is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Overall, the high and acceptable COD removal efficiency were observed in two different scenarios of operation. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the average COD removal efficiency in scenario 1 and OLR equal to 2.15 kgCOD/m\u003csup\u003e3\u003c/sup\u003ed (93.92%) was higher than that for scenario 2 and OLR of 2.45 kgCOD/m\u003csup\u003e3\u003c/sup\u003ed (90.94%)(p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.008).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eC. Visvanathan and et al. (2008) investigated the Hydrogenotrophic denitrification of synthetic aquaculture wastewater using membrane bioreactor. The authors reported that in MBR reactors are able to remove 80\u0026ndash;90% COD equal to 50 mg/L created with addition the fish food, excreta and glucose with operational condition of HRT of 2\u0026ndash;9 h [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. These results are comparable with the present study. L. Rodr\u0026iacute;guez-Hern\u0026aacute;ndez and et al. (2014) surveyed the COD removal efficiency on the fixed bed hybrid membrane bioreactor by adding the biofilm and support media. The results indicated that the fixed bed MBR are able to better remove COD (84%) compared to that for conventional MBR (80%); the COD of effluent from fixed bed MBR and conventional MBR were 54 and 65 mg/L, respectively [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The high growth of biofilm on the packing bed of FBMR is the most possible reason for high COD removal efficiency [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e3.1.2. BOD removal efficiency\u003c/h2\u003e\u003cp\u003eThe BOD variation for wastewater, the effluent of FBMR and BOD removal efficiency for different OLR scenario within the study period are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. A shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e the initial BOD of the wastewater entering the reactor and treatment system ranged from 235 to 283 mg/L, with only minor fluctuations observed between the anoxic reactor and the FBMBR unit. Over the 180-day study period, the effluent from the FBMBR exhibited an average BOD of 22 mg/L, with values ranging from a minimum of 14 mg/L to a maximum of 25 mg/L. Additionally, the temporal pattern of BOD removal efficiency throughout the study is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Generally, the high and acceptable BOD removal efficiency were achieved in two different scenarios of operation. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the average BOD removal efficiency in scenario 1 and OLR equal to 2.15 kgCOD/m\u003csup\u003e3\u003c/sup\u003ed (91.78%) was higher than that for scenario 2 and OLR of 2.45 kgCOD/m\u003csup\u003e3\u003c/sup\u003ed (85.73%) (p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.008).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003ePalmarin J and et al. (2019) surveyed the treatment performance of a hybrid MBR equipped with biocarrier for greywater reclamation [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The initial BOD for the graywater was 150 mg/L. The results indicated that the hybrid MBR are able to remove BOD until 97%; the BOD in the effluents were 4\u0026thinsp;\u0026plusmn;\u0026thinsp;2 mg BOD/L. L. Rodr\u0026iacute;guez-Hern\u0026aacute;ndez and et al. (2014) investigated treatment performance of municipal wastewater with initial BOD equal to 39 mg/ L using the FBMBR [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The result indicated that the FBMBR with HRT\u0026thinsp;=\u0026thinsp;24 h are able to remove BOD until 98%. The main possible reason for the differences of these values reported here and the present study are attributed to low initial BOD of wastewater.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e3.1.3. TKN and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e removal efficiency\u003c/h2\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cb\u003e(a- b)\u003c/b\u003e illustrate the TKN and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e variation in the raw wastewater and the effluent from the FBMBR and in addition the removal efficiency based on the different OLR scenario. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cb\u003e(a)\u003c/b\u003e, the initial TKN of wastewater fed into reactor and treatment process were between 59 and 69 mg/L with a little variation in wastewater fed into anoxic container and FBMBR. The average TKN in the effluent from the FBMBR and TKN removal efficiency were estimated to be 16 mg/L (min: 11 mg/L, max: 22 mg/L) and 74.12% (min: 62.07%, max: 81.67%), respectively.\u003c/p\u003e\u003cp\u003eFurthermore, the NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e in effluent from FBMBR and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e removal efficiency is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cb\u003e(b).\u003c/b\u003e As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cb\u003e(b)\u003c/b\u003e, the average NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e in the effluent from the FBMBR and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e removal efficiency were estimated to be 2.81 mg/L (min: 2.16 mg/L, max: 3.05 mg/L) and 92.32% (min: 90.35%, max: 94.98%), respectively.\u003c/p\u003e\u003cp\u003eL. Rodr\u0026iacute;guez-Hern\u0026aacute;ndez and et al. (2014) surveyed the removal efficiency of TN and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e in a hybrid membrane bioreactor (HMBR), developed by addition the biofilm support media. The results indicated that the TKN and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e removal efficiency were 75% and 95%, respectively with initial concentration levels of 39 mg/L and 0.4 mg/L, respectively [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. These values and removal efficiency are comparable with the results presented here. In addition, Hee Seok Kim (2008) investigated the enhanced nitrogen removal efficiency from the piggery wastewater by MBR combined with nitrification process. The results indicated that 68% of initial ammonia were removed by this process (initial NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e in the wastewater: 2560 mg/L) [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The presence of attached biofilm on the fixed bed MBR prevention the oxygen diffusion into biofilm and the presence of aeration intensity (high ambient DO) in the reactor with small size flock are the most possible reason for TN and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e removal due to nitrification and denitrification process [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e3.1.3. TP removal efficiency\u003c/h2\u003e\u003cp\u003eThe TP removal efficiency variation from the treatment process equipped with anoxic and FBMBR are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. As can be seen from the Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the highest TP removal efficiency (66.03%) was achieved in the lower OLR; the average TP removal efficiency within the study period was 57%. The variation of concentration levels of TP in the effluent of FBMBR are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The average TP concentration level in the effluent of FBMBR were 2.6 mg/L (min: 2.21 mg/L and max: 2.81 mg/L). L. Rodr\u0026iacute;guez-Hern\u0026aacute;ndez and et al. (2014) Reported that a hybrid membrane bioreactor (HMBR) with biofilm support media are able to remove the TP by 42%; the concentration levels of PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e in the effluent of HMBR was estimated to be 2.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 mg/ L, which is similar to the results presented here [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The effective removal of total phosphorus (TP) in the FBMBR system is primarily attributed to the growth of biomass, particularly phosphorus-accumulating organisms (PAOs) on the biofilm, along with the presence of anoxic and anaerobic zones within the support media [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eA comprehensive study was designed to survey the treatment efficiency of combined anoxic and fixed bed MBR (FBMBR) in nutrient removal from the municipal wastewater. Here, the comprehensive study was developed to survey the roles of combined anoxic and FBMBR in treatment efficiency of municipal wastewater containing high concentration levels of nutrients. In addition, the roles of different OLD on the operational parameters including COD, BOD, TN and TP were examined. The results from the present study indicated that this combined biological method led to efficient removal of pollutants and nutrients from the wastewater. The highest removal efficiency for TN (94.98%) and TP (57%) were achieved within the study period, this combined method (anoxic\u0026thinsp;+\u0026thinsp;FBMBR) is a feasible and promising technology to treat the municipal wastewater containing high levels of nutrients.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present study was funded by West Tehran branch, Islamic Azad University, Tehran, Iran.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMahbubeh Ezzati Shourgoli\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eMethodology, Investigation, Writing. \u003cstrong\u003eAmir Hessam Hassani:\u0026nbsp;\u003c/strong\u003eConceptualization, Supervision, Editting. \u003cstrong\u003eAmirhossein Javid\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eMethodology, investigation. \u003cstrong\u003eRoya Mafigholami\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;and Rouhallah Mahmoudkhani:\u0026nbsp;\u003c/strong\u003eInvestigation, Analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research did not receive any funding.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and analyzed during the current study were available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial declarations:\u003c/strong\u003e Not applicable\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eManasa RL, Mehta A. Current perspectives of anoxic ammonia removal and blending of partial nitrifying and denitrifying bacteria for ammonia reduction in wastewater treatment. J Water Process Eng. 2021;41:102085. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jwpe.2021.102085\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2021.102085\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVisvanathan C, Hung NQ, Jegatheesan V. Hydrogenotrophic denitrification of synthetic aquaculture wastewater using membrane bioreactor. Process Biochem. 2008;43:673\u0026ndash;82. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.procbio.2008.02.007\u003c/span\u003e\u003cspan address=\"10.1016/j.procbio.2008.02.007\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBartlett R, Mortimer RJG, Morris K. Anoxic nitrification: evidence from Humber Estuary sediments (UK). Chem Geol. 2008;250:29\u0026ndash;39.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMorris S, Garcia-Cabellos G, Ryan D, Enright D, Enright A-M. Low-cost physicochemical treatment for removal of ammonia, phosphate and nitrate contaminants from landfill leachate. J Environ Sci Heal Part A. 2019;54:1233\u0026ndash;44.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFu Q, Zheng B, Zhao X, Wang L, Liu C. Ammonia pollution characteristics of centralized drinking water sources in China. J Environ Sci. 2012;24:1739\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYao J, Mei Y, Xia G, Lu Y, Xu D, Sun N, Wang J, Chen J. Process optimization of electrochemical oxidation of ammonia to nitrogen for actual dyeing wastewater treatment. Int J Environ Res Public Health. 2019;16:2931.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShin JH, Sang BI, Chung YC, kyoo Choung Y. A novel CSTR-type of hollow fiber membrane biofilm reactor for consecutive nitrification and denitrification. Desalination. 2008;221:526\u0026ndash;33. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.desal.2007.01.113\u003c/span\u003e\u003cspan address=\"10.1016/j.desal.2007.01.113\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJegatheesan V, Zeng C, Shu L, Manicom C, Steicke C. Technological advances in aquaculture farms for minimal effluent discharge to oceans. J Clean Prod. 2007;15:1535\u0026ndash;44.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAtkins PF Jr, Scherger DA, Barnes RA, Evans FL. III, Ammonia removal by physical-chemical treatment. J (Water Pollut Control Fed. (1973) 2372\u0026ndash;88.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWalter B, Haase C, R\u0026auml;biger N. Combined nitrification/denitrification in a membrane reactor. Water Res. 2005;39:2781\u0026ndash;8. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.watres.2005.04.027\u003c/span\u003e\u003cspan address=\"10.1016/j.watres.2005.04.027\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSarioglu M, Insel G, Artan N, Orhon D. Model evaluation of simultaneous nitrification and denitrification in a membrane bioreactor operated without an anoxic reactor. J Memb Sci. 2009;337:17\u0026ndash;27. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.memsci.2009.03.015\u003c/span\u003e\u003cspan address=\"10.1016/j.memsci.2009.03.015\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eInsel G. Effects of design and aeration control parameters on simultaneous nitrification and denitrification (SNdN) performance for activated sludge process. Environ Eng Sci. 2007;24:675\u0026ndash;86.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRahman TU, Roy H, Islam MR, Tahmid M, Fariha A, Mazumder A, Tasnim N, Pervez MN, Cai Y, Naddeo V. The advancement in membrane bioreactor (MBR) technology toward sustainable industrial wastewater management. Membr (Basel). 2023;13:181.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMannina G, Alliet M, Brepols C, Comas J, Harmand J, Heran M, Kalboussi N, Makinia J, Robles \u0026Aacute;, Rebou\u0026ccedil;as TF. Integrated membrane bioreactors modelling: A review on new comprehensive modelling framework. Bioresour Technol. 2021;329:124828.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eIorhemen OT, Hamza RA, Tay JH. Membrane bioreactor (MBR) technology for wastewater treatment and reclamation: membrane fouling. Membr (Basel). 2016;6:33.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDeng L, Guo W, Ngo HH, Wang XC, Hu Y, Chen R, Cheng D, Guo S, Cao Y. Application of a specific membrane fouling control enhancer in membrane bioreactor for real municipal wastewater treatment: sludge characteristics and microbial community. Bioresour Technol. 2020;312:123612.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAbbassi R, Yadav AK, Huang S, Jaff\u0026eacute; PR. Laboratory study of nitrification, denitrification and anammox processes in membrane bioreactors considering periodic aeration. J Environ Manage. 2014;142:53\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jenvman.2014.03.013\u003c/span\u003e\u003cspan address=\"10.1016/j.jenvman.2014.03.013\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eW. APHA, AWWA. Standard Methods for examination of water and wastewater, 2017.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRodr\u0026iacute;guez-Hern\u0026aacute;ndez L, Esteban-Garc\u0026iacute;a AL, Tejero I. Comparison between a fixed bed hybrid membrane bioreactor and a conventional membrane bioreactor for municipal wastewater treatment: A pilot-scale study. Bioresour Technol. 2014;152:212\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.biortech.2013.10.081\u003c/span\u003e\u003cspan address=\"10.1016/j.biortech.2013.10.081\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eArya V, Philip L, Bhallamudi SM. Performance of suspended and attached growth bioreactors for the removal of cationic and anionic pharmaceuticals. Chem Eng J. 2016;284:1295\u0026ndash;307.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePalmarin MJ, Young S. Comparison of the treatment performance of a hybrid and conventional membrane bioreactor for greywater reclamation. J Water Process Eng. 2019;28:54\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jwpe.2018.12.012\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2018.12.012\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFathali D, Rashidi Mehrabadi A, Mirabi M, Alimohammadi M. Investigation on nitrogen removal performance of an enhanced post-anoxic membrane bioreactor using disintegrated sludge as a carbon source: An experimental study. J Environ Chem Eng. 2019;7:103445. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jece.2019.103445\u003c/span\u003e\u003cspan address=\"10.1016/j.jece.2019.103445\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim HS, Choung YK, Ahn S, Oh HS. Enhancing nitrogen removal of piggery wastewater by membrane bioreactor combined with nitrification reactor. Desalination. 2008;223:194\u0026ndash;204. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.desal.2006.12.021\u003c/span\u003e\u003cspan address=\"10.1016/j.desal.2006.12.021\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu Q, Wang XC, Liu Y, Yuan H, Du Y. Performance of a hybrid membrane bioreactor in municipal wastewater treatment. Desalination. 2010;258:143\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Membrane Reactor, Biological Reactor, Nitrogen, Phosphorous, Anoxic","lastPublishedDoi":"10.21203/rs.3.rs-7847046/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7847046/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA comprehensive study was developed to investigate the roles of combined anoxic and fixed bed MBR (FBMBR) in nutrient removal from the municipal wastewater. The performance of anoxic\u0026thinsp;+\u0026thinsp;FBMBR in different organic loading rate (OLR) (0.58, 2.15 and 2.45 kg COD/m\u003csup\u003e3\u003c/sup\u003e.day) in terms of COD, BOD, total nitrogen (TN) and total phosphorus (TP) with study period of 180 days. The results indicated that the highest removal efficiency for COD (93.92%) was obtained in ORL equal to 2.15 kgCOD/m\u003csup\u003e3\u003c/sup\u003ed (93.92%). However, the COD removal efficiency for OLR equal to 2.45 kgCOD/m\u003csup\u003e3\u003c/sup\u003ed was promising (90.94%). In case of nutrients, the highest removal efficiency for TN and TP within the study period were 94.98% and 57%, respectively and meet the standards for discharge to the environment. Therefore, the combined anoxic and FBMBR is a promising technology for efficient removal of nutrients from the municipal wastewater with high concentration levels of nutrients.\u003c/p\u003e","manuscriptTitle":"A comprehensive study on nutrient removal from domestic wastewater by integrated anoxic and fixed-bed membrane bioreactors","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-05 12:49:23","doi":"10.21203/rs.3.rs-7847046/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d6f413e2-bf54-43ce-b8b8-5ebf577deb4e","owner":[],"postedDate":"November 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-06T06:53:15+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-05 12:49:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7847046","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7847046","identity":"rs-7847046","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}