Optimization of SBR Biological Treatment System and Advanced Oxidation for Non-Biodegradable Gray Water Treatment

Optimization of SBR Biological Treatment System and Advanced Oxidation for Non-Biodegradable Gray Water Treatment | 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 Article Optimization of SBR Biological Treatment System and Advanced Oxidation for Non-Biodegradable Gray Water Treatment Saeid Govahi, Ehsan Derikvand, Saeb Khoshnavaz, Mohsen Solimani Babarsad, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4021079/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 This study investigates the treatment of gray water with high detergent content through a combination system of sequential batch reactor (SBR) and UV/H2O2 chemical oxidation. Preliminary analysis showed COD, BOD, TP and TKN levels of 600, 200, 4 and 15 mg/L respectively. As a result of SBR treatment, BOD5 decreased from 270 to 40 mg/L and COD from 600 to 162 mg/L. Activated carbon powder showed the least effect on pollutant removal efficiency. The optimal concentration of H2O2 was 12 mg/L and the duration of 3 hours for chemical oxidation was determined. The duration of aerobic and anaerobic SBR more than 4 and 2 hours, respectively, had negligible effects on pollutant removal. The combined SBR and chemical oxidation system achieved removal efficiencies of 90.6, 85, 82.5, and 65% for COD, BOD, TP, and TKN, respectively. Placing chemical oxidation before biological treatment increased organic compound removal by 6% because chemical oxidation increased biodegradable compounds. In addition, using an anaerobic unit to remove phosphorus before aeration was effective, more than two hours of anaerobic treatment had no effect on the removal of dissolved phosphorus. Biological sciences/Biological techniques Earth and environmental sciences/Environmental sciences Physical sciences/Energy science and technology Biological Chemical oxidation Gray water Treatment Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Gray water refers to untreated domestic wastewater from the sink of the toilets, showers, kitchens, and laundry basins. In other words, it refers to all non-toilet uses 1 . It is estimated that gray water accounts for 65–85% of the total household water consumption 2 . In houses with more than one water tap inside the house, 180–300 liters per day is calculated for each person. In houses where the water tap is outside the house, this amount is 30–80. In houses located at a distance of 250 meters or more than the standpipe, it decreases to 9–50 2 . This water is a significant source for irrigating gardens and growing food crops. The amounts of alkaline substances, Ca, Cl, B, K, Na, total coliforms, and E. coli are significant 3 . The use of polluted gray water can have negative impacts on human health and the environment, especially on plants and irrigated soil. Great efforts have been made in the area of wastewater reuse and its implementation. This global effort is due to the lack of freshwater resources, rising welfare levels, and increasing demand due to population expansion. Australia is the driest country facing water scarcity which is exacerbated by climate change, and some predictions refer to a difficult scenario for future water supply, especially in southern and eastern Australia 4 . Thus, the reuse of wastewater for environmental and economic benefits is effective for the sustainable management of water resources 5 . Based on traditional management, wastewater is sent to the treatment plant after mixing with water. Since the quality of the treatment plant output is similar to gray water 6 , Gutter argued that the separation of gray water at the production site facilitates its reuse. Studies have discussed its recycling extensively 5 b, 7 . The quantity and quality of gray water even in the same house are significantly variable due to the different conditions of the production process 7 a . Biochemical oxygen demand has been reported at 5-1460 mg/L, chemical oxygen demand at 13-8000 mg/L, pH around 8–10 and water turbidity at 15–240 NTU, and suspended solids at 17–330 mg/l 5 a . Detergents are one of the most significant wastewater pollutants that significantly affect the performance of microorganisms. Linear alkyl benzene sulfonates (LAS) are among the most significant ionic detergents that are present in household detergents such as laundry and dishwashing detergents. Thanks to their biological degradability, these materials have replaced non-linear alkyl benzene sulfonates (ABS) that are degraded hardly 8 . Gray water treatment technology includes simple storage and complex systems based on advanced chemical oxidation processes and physical and biological treatment. Advanced Oxidation Process (AOP) has been extensively applied in the treatment of drinking water and domestic and industrial wastewater. However, their application in gray water treatment has been limited to photo catalysis. At a laboratory scale, pine bark, activated charcoal, and sand filters were investigated to remove pollution, and the relationship between substrate, effluent, and bacteria was examined. Using the general regression models, the effects of hydraulic and organic loading rates of HLR and OLR were investigated. The quality of domestic wastewater was evaluated against Jordanian standards for irrigation water. Charcoal showed a good capability to remove BOD (83–97%), TKN (50–98%), and TP (64–98%) thanks to its high specific surface. The BOD removal rate in the sand filter is low and it is about (67 to 91%), and the total nitrogen removal was small. Tree bark and charcoal showed good results in removing organic compounds for irrigation, and other systems should be used to remove nitrogen and bacteria 9 . Studies were conducted on several absorbents to remove phosphorus from wastewater. Most of them contained calcium and pH above 7. The highest phosphorus removal rate was related to industrial absorbents such as furnace ash, which removed up to (420 grams) of phosphorus per kilogram of absorbent. The removal rate of phosphorus in natural materials was about (40 grams). This study revealed a good relationship between the lime and phosphorus absorption levels and the pH level showed little effect. Other influential parameters such as hydraulic load, saturation percentage, type of filter material, and its availability in the absorption rate need to be investigated 10 . Three systems for the biological treatment of domestic wastewater were compared at the same hydraulic residence time of 12 to 13 hours in 2010 11 . These systems included the aerobic process in sequential discontinuous SBR reactors, the anaerobic process in the UASB system, and the combination of them. COD removal was higher than (90%) in aerobic conditions and it was almost (51%) in anaerobic systems. The low removal of COD in the anaerobic reactor may be due to the high concentration of anionic surfactant in the inlet (43.5 mg/L) and poor removal of colloidal organic compounds. COD removal was reported to be higher than (89%) in the combined aerobic-anaerobic treatment system, which was similar to aerobic treatment. Domestic gray water Methanogens was (32%) for anaerobic systems and (25%) for anaerobic-aerobic systems, which produced little energy. Thus, anaerobic pretreatment is not practical, and aerobic gray water treatment is preferred 11 . METHODS A biological treatment system and a chemical oxidation system were used to conduct this system, as shown in the (Figs. 1 and 2 ) . In the biological treatment system, a plastic container with a volume of 8 liters was used, (60%) of which was filled with sludge from the extensive aeration wastewater treatment plant. (Tables 1 and 2 ) presents the gray wastewater compounds and Quality characteristics. The SBR reactor started working for one month to adapt the sludge to the gray water. The SBR reactor included six phases filling, anaerobic, aeration, anoxic, settling, and discharge. The MLSS amount after one month in the aeration part was 2800 mg/l and SVI was 95 ml/g, which is suitable for biological treatment. Aeration was done with an aquarium pump to the extent that dissolved oxygen in the aerobic system was above 5 mg/liter. Two UV lamps with a power of 15 watts are placed on the ceiling of a glass box with dimensions of 80x20x15. It was covered with aluminum foil so it did not have contact with water for radiation. The distance between the lamps and the water was 5 cm. The environment temperature varied between 25 and 35°C. The stirrer speed in the SBR unit was about 50 RPM. To increase the biological treatment efficiency, granular activated carbon Norit GAC 830 was used with an effective size of 0.9 mm, uniformity coefficient of 1.7, and an effective surface area of 975 m2/g. Gray water samples were kept at 4°C and tested up to 48 hours. Table 1 gray water compounds Compound Unit in 20 liters of water Value laundry detergent mg 200 Meat extract mg 600 Cake flour mg 15 Soap Body mg 4 Oil mg 0.01 Table 2 gray water characterization Compound Unit Value BOD 5 Mg/l 200 COD Mg/l 600 pH - 9 TSS Mg/l 25 TDS Mg/l 800 Cl Mg/l 26 TKN Mg/l 15 TP Mg/l 4 Results COD removal rate with aeration time in the SBR system The removal rate of COD and BOD 5 of synthetic gray water with COD = 600 mg/l and BOD5 = 270 mg/l with a volume of 3 liters for 24 hours in an SBR reactor was investigated in filling, anaerobic, aeration, anoxic, and settling phases. The aerobic and anaerobic stages were continued for 6 and 12 hours to determine the performance of the system at different times for optimization, as shown in (Fig. 3 ) . COD removal efficiency in anaerobic, aeration, and total phases was 46, 34, and 73%, respectively. BOD 5 removal in anaerobic, aerobic, and total stages was measured at 65.5, 52.5, and 85% respectively. BOD 5 of gray water after SBR was reduced from 270 to 40 and COD from 600 to 162 mg/L. During the first two and four hours of the anaerobic and aeration phases, COD and BOD 5 were removed at the highest rate, while the removal of organic matter decreased over time, so the duration of anaerobic and aeration more than 2 and 4 hours will not be useful in pollutant removal. The high removal efficiency was not observed due to the high concentration of detergents and the low concentration of biodegradable compounds, so the BOD/COD ratio after SBR was 0.25. Thus, biological treatment alone cannot remove the organic compounds of this type of gray water for discharge into the environment. Phosphorus and nitrogen removal rate in SBR system Gray water with phosphorus and nitrogen content of 4 and 15.1 mg/L entered the SBR reactor in a volume of 3 liters and followed the steps of filling, anaerobic, aeration, anoxic, settling, and discharge. (Fig. 4 ) illustrates that the phosphate concentration in the water increases over time in the anaerobic phase up to 2 hours, but then remains constant until 6 hours. In other words, soluble phosphorus can increase up to two hours in anaerobic conditions, and longer times have no impact on phosphorus removal. Ammonia nitrogen and phosphate concentrations were reduced from 15.1 and 13.2 to 5.26 and 0.7 mg/liter after 5 hours of aeration. Increasing the aeration time up to 12 hours showed little impact on ammonia nitrogen removal. Thus, the anaerobic and aeration time of 2 and 5 hours is sufficient and optimal to remove a maximum of 82.5% of phosphorus and 65% of ammonia nitrogen. The effect of using granular activated carbon in pollution removal Based on the optimal conditions of the previous stages, the duration of filling, anaerobic, aerobic, anoxic, and settling phases was 2 minutes, 2, 4, 1, and 4 hours, respectively. In the SBR reactor, granular activated carbon was added from 250 to 1250 mg/liter, respectively, as suggested by previous studies in the aeration part. As shown in (Fig. 5 ) , the COD, NH 4 , and PO 4 removal efficiency increases slightly as the granular activated carbon concentration increases and has almost no effect. The effect of pH and residence time on gray water COD removal in the UV/H2O2 process Synthetic gray water after biological treatment with COD = 170 mg/l was subjected to UV/H2O2 chemical oxidation. COD removal rate regarding residence time and pH can be seen in (Fig. 6 ). The COD removal efficiency at a fixed contact time of 3 hours and pH of 2, 4, 6, 8, 10, 12, and 14 was observed to be 65, 71, 73, 78, 81, 62, and 49%, respectively. At constant residence time, the removal efficiency of organic compounds increased slightly with increasing pH. Optimal dose of H 2 O 2 to remove organic pollution The gray water discharged from the SBR with a COD of 170 mg/L was subjected to UV/H 2 O 2 chemical oxidation. According to the results of the previous stage, the pH and irradiation time were fixed at 10 and 3 hours, respectively. Based on (Fig. 7 ) , in the combined system with the dose of 0, 3.5, 5, 7, 12, 15, and 20 mg/L H2O2, the output COD values were measured at 170, 90, 78, 65, 56, 56, and 56 mg/L. The effect of chemical oxidation before and after biological treatment In the optimal conditions of SBR and the chemical oxidation process, obtained from the previous stages, the gray wastewater first goes through UV/H 2 O 2 chemical oxidation and then enters the SBR reactor. COD, NH 4 , and PO 4 in the output are 18, 5.25, and 0.72 mg/liter, respectively. As shown in (Fig. 8 ) , the COD removal efficiency is (97%) if the chemical oxidation process is performed before biological treatment. It is (6%) more than before, but the efficiency of phosphorus and nitrogen removal did not change compared to before. Discussion COD and BOD 5 were removed with the highest rates during the first two and four hours of the anaerobic and aeration phases, while the removal of organic matter decreased over time, so the duration of anaerobic and aeration more than 2 and 4 hours will not be useful in pollutant removal. Given the high concentration of detergents in gray water and the low concentration of biodegradable compounds, high removal efficiency was not observed so the ratio of BOD/COD after SBR was 0.25. Thus, biological treatment alone cannot remove organic compounds to discharge into the environment. Gray water with phosphorus and nitrogen content of 4 and 15.1 mg/L entered the SBR reactor in a volume of 3 liters and followed the steps of filling, anaerobic, aeration, anoxic, settling, and discharge. Polyphosphate-accumulating organisms (PAOs) grow faster in anaerobic conditions and convert phosphorus into polyphosphate 12 . Aerobic processes alone cannot remove total phosphorus. To remove all phosphorus from the system, the anaerobic process should release it as polyphosphate 13 . Polyphosphate is removed faster due to the presence of nitrate as an electron acceptor during the aerobic phase 14 . Thus, it is useful to use an anaerobic unit to remove phosphorus before aeration. Soluble phosphorus can increase up to two hours in anaerobic conditions, and longer times have no impact on phosphorus removal. Nitrification occurs during the aeration process, which reduces ammonia nitrogen. Ammonia nitrogen and phosphate concentrations were reduced from 15.1 and 13.2 to 5.26 and 0.7 mg/liter, respectively, after 5 hours of aeration. Increasing the aeration time up to 12 hours showed little impact on ammonia nitrogen removal. It does not help to remove nitrogen and phosphorus. Thus, the anaerobic and aeration times of 2 and 5 hours, respectively, are optimal to remove a maximum of (82.5%) of phosphorus and (65%) of ammonia nitrogen. Based on the optimal conditions, the time of filling, anaerobic, aerobic, anoxic, and settling phases were obtained at 2 minutes, 2, 4, 1, and 4 hours, respectively. Laminate in gray water treatment showed better nitrification than SBR with a residence time of 2.5 days. During the residence time of 2.5 days, the concentration of phosphate remained fixed in the anoxic phase and decreased slightly in the aeration phase. The final phosphate concentration was observed at 3 mg/l 15 . Fountoulakis showed that COD/BOD must be less than 2 mg/l to remove phosphorus. If there are fatty acids resulting from anaerobic decomposition, phosphorus will not be removed 16 . Another study in 2016 revealed the duration of aeration and anaerobic should be changed to remove phosphorus 17 . Studies have shown that the surfactant in gray water is toxic to anaerobic bacteria 18 . Other studies have reported that LAS reduces the activity of anaerobic bacteria 19 and surfactants stop the methanogenic phase 20 . Granular activated carbon was used to increase the removal efficiency of organic compounds, nitrogen, and phosphorus in SBR, but a very small positive impact was observed. Previous studies have recommended the use of granular activated carbon in the removal of COD, NH4, and PO4 in the biological treatment of slaughterhouse wastewater 21 . Moving forward, further investigations into optimizing the application parameters of activated carbon, as well as exploration of alternative treatment strategies, may be warranted to address the persistent challenge of pollutant removal in gray water treatment systems. COD removal efficiency decreases at pH values greater than 10 after biological treatment in the chemical oxidation process. This is because H 2 O 2 is converted to H2O and O2 at high pH and a small amount of H 2 O 2 remains in the treated water. The effect of pH on the removal rate of organic compounds is negligible at pH values below 10. The effect of pH on the removal of organic compounds decreases in the presence of carbonate or bicarbonate, and more than 300 mg/L based on CaCo 3 negatively affects chemical oxidation 22 . Based on Fig. 5 , the COD removal efficiency was measured at (91%) at a residence time of 3 hours. Results obtained by Tokhanen in 1997 were different. In this study, acidic conditions with a residence time of 2 hours were more effective 23 . The HCo 3 and CO 3 formation in high alkalinity conditions showed a negative impact on chemical oxidation. UV/H 2 O 2 reduces pH values due to the conversion of organic matter into mineral acids and carbon dioxide 24 . The concentration of produced hydroxyl decreases and the removal power of organic compounds decreases with an excessive increase in H 2 O 2 25 . The COD removal rate in chemical oxidation and combined system with SBR was (67% and 90.6%), respectively. Irradiation of water or wastewater containing H 2 O 2 with UV rays produces hydroxyl radicals. UV rays break down H 2 O 2 into hydroxyl radicals. Organic compounds are easily oxidized by hydroxyl radicals 26 . Hassanshahi removed (92.1%) of COD using a combined UV/H 2 O 2 /O 3 system with a dose of 200 mg/L H 2 O 2 , an O 3 concentration of 150 mg/L, and a residence time of 4 hours at pH = 68 27 . The use of chemical oxidation as a pre-treatment of the SBR system increased the COD removal efficiency by (6%). Its reason may be the breakdown of non-degradable compounds and the increase of the BOD/COD ratio due to UV rays and the chemical oxidation process 28 . Declarations Author Contribution Saeid govahi : original text of research and pilot constructionEhsan Derikvand: text of the original research and pilot constructionSaeb Khoshnavaz: research methodMohsen Soleimani Babrasad: analysis of the resultsIman Parseh: research background References S. Tsoumachidou, T. Velegraki, A. Antoniadis, I. Poulios, Journal of environmental management 2017, 195, 232. K. Carden, N. Armitage, K. Winter, O. Sichone, U. Rivett, J. Kahonde, Water SA 2007, 33. N. Rodda, L. Salukazana, S. Jackson, M. T. Smith, Physics and Chemistry of the Earth, Parts A/B/C 2011, 36, 1051. B. Pittock, Water: Journal of the Australian Water Association 2007, 34, 42. a)E. Eriksson, K. Auffarth, A. M. Eilersen, M. Henze, A. Ledin, Water Sa 2003, 29, 135; b)V. Lazarova, S. Hills, R. Birks, Water Science and Technology: Water Supply 2003, 3, 69. F. Günther, Ecological Engineering 2000, 15, 139. a)B. Jefferson, J. E. Burgess, A. Pichon, J. Harkness, S. J. 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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-4021079","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":283325356,"identity":"913da218-bed5-42ae-9301-97e421c4c741","order_by":0,"name":"Saeid Govahi","email":"","orcid":"","institution":"Department of Water Sciences, Shoushtar Branch, Islamic Azad University, Shoushtar, Iran.","correspondingAuthor":false,"prefix":"","firstName":"Saeid","middleName":"","lastName":"Govahi","suffix":""},{"id":283325357,"identity":"a706e9ed-aaad-4b01-b433-78734c01ffa4","order_by":1,"name":"Ehsan 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4","display":"","copyAsset":false,"role":"figure","size":134099,"visible":true,"origin":"","legend":"\u003cp\u003eRate of phosphorus and nitrogen removal in SBR\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4021079/v1/47ad89df23ddaf1abe05d977.jpg"},{"id":53424934,"identity":"23f3b523-f757-4316-895a-ee43eb6381a0","added_by":"auto","created_at":"2024-03-25 19:56:39","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":76870,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of granular activated carbon in the removal of pollutants\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4021079/v1/f1f18deaff82abc03fe6c3e7.jpg"},{"id":53424932,"identity":"91dec460-9c4c-4977-bb88-a4b7f7f7499a","added_by":"auto","created_at":"2024-03-25 19:56:39","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":89234,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of pH and residence time on COD removal\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4021079/v1/c4649dad8e07a55ad1f1a01d.jpg"},{"id":53424928,"identity":"ddfa7ab3-93b7-4c79-a419-39bd9ce7f668","added_by":"auto","created_at":"2024-03-25 19:56:38","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":149134,"visible":true,"origin":"","legend":"\u003cp\u003eOptimal concentration of H2O2 for removing organic pollutants\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4021079/v1/34ee9c159267c7488539bacd.jpg"},{"id":53424937,"identity":"01b2e07e-aac8-4676-8680-e2ee15d0c744","added_by":"auto","created_at":"2024-03-25 19:56:40","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":372113,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of using chemical oxidation before and after biological treatment\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4021079/v1/4e423c642fc8c1a08e1b9f24.jpg"},{"id":53836194,"identity":"ae95cb78-c818-4cb6-8461-35be9d1ad35d","added_by":"auto","created_at":"2024-04-01 06:16:11","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":673868,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4021079/v1/d9bcbed3-258a-43e3-8f41-f9ea77837170.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optimization of SBR Biological Treatment System and Advanced Oxidation for Non-Biodegradable Gray Water Treatment","fulltext":[{"header":"Introduction","content":"\u003cp\u003eGray water refers to untreated domestic wastewater from the sink of the toilets, showers, kitchens, and laundry basins. In other words, it refers to all non-toilet uses \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. It is estimated that gray water accounts for 65\u0026ndash;85% of the total household water consumption \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. In houses with more than one water tap inside the house, 180\u0026ndash;300 liters per day is calculated for each person. In houses where the water tap is outside the house, this amount is 30\u0026ndash;80. In houses located at a distance of 250 meters or more than the standpipe, it decreases to 9\u0026ndash;50 \u003csup\u003e2\u003c/sup\u003e. This water is a significant source for irrigating gardens and growing food crops. The amounts of alkaline substances, Ca, Cl, B, K, Na, total coliforms, and E. coli are significant \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. The use of polluted gray water can have negative impacts on human health and the environment, especially on plants and irrigated soil. Great efforts have been made in the area of wastewater reuse and its implementation. This global effort is due to the lack of freshwater resources, rising welfare levels, and increasing demand due to population expansion. Australia is the driest country facing water scarcity which is exacerbated by climate change, and some predictions refer to a difficult scenario for future water supply, especially in southern and eastern Australia \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Thus, the reuse of wastewater for environmental and economic benefits is effective for the sustainable management of water resources \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBased on traditional management, wastewater is sent to the treatment plant after mixing with water. Since the quality of the treatment plant output is similar to gray water \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e, Gutter argued that the separation of gray water at the production site facilitates its reuse. Studies have discussed its recycling extensively \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003eb, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The quantity and quality of gray water even in the same house are significantly variable due to the different conditions of the production process \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003ea\u003c/sup\u003e. Biochemical oxygen demand has been reported at 5-1460 mg/L, chemical oxygen demand at 13-8000 mg/L, pH around 8\u0026ndash;10 and water turbidity at 15\u0026ndash;240 NTU, and suspended solids at 17\u0026ndash;330 mg/l \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003ea\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDetergents are one of the most significant wastewater pollutants that significantly affect the performance of microorganisms. Linear alkyl benzene sulfonates (LAS) are among the most significant ionic detergents that are present in household detergents such as laundry and dishwashing detergents. Thanks to their biological degradability, these materials have replaced non-linear alkyl benzene sulfonates (ABS) that are degraded hardly \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Gray water treatment technology includes simple storage and complex systems based on advanced chemical oxidation processes and physical and biological treatment. Advanced Oxidation Process (AOP) has been extensively applied in the treatment of drinking water and domestic and industrial wastewater. However, their application in gray water treatment has been limited to photo catalysis.\u003c/p\u003e \u003cp\u003eAt a laboratory scale, pine bark, activated charcoal, and sand filters were investigated to remove pollution, and the relationship between substrate, effluent, and bacteria was examined. Using the general regression models, the effects of hydraulic and organic loading rates of HLR and OLR were investigated. The quality of domestic wastewater was evaluated against Jordanian standards for irrigation water. Charcoal showed a good capability to remove BOD (83\u0026ndash;97%), TKN (50\u0026ndash;98%), and TP (64\u0026ndash;98%) thanks to its high specific surface. The BOD removal rate in the sand filter is low and it is about (67 to 91%), and the total nitrogen removal was small. Tree bark and charcoal showed good results in removing organic compounds for irrigation, and other systems should be used to remove nitrogen and bacteria \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Studies were conducted on several absorbents to remove phosphorus from wastewater. Most of them contained calcium and pH above 7. The highest phosphorus removal rate was related to industrial absorbents such as furnace ash, which removed up to (420 grams) of phosphorus per kilogram of absorbent. The removal rate of phosphorus in natural materials was about (40 grams). This study revealed a good relationship between the lime and phosphorus absorption levels and the pH level showed little effect. Other influential parameters such as hydraulic load, saturation percentage, type of filter material, and its availability in the absorption rate need to be investigated \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThree systems for the biological treatment of domestic wastewater were compared at the same hydraulic residence time of 12 to 13 hours in 2010 \u003csup\u003e11\u003c/sup\u003e. These systems included the aerobic process in sequential discontinuous SBR reactors, the anaerobic process in the UASB system, and the combination of them. COD removal was higher than (90%) in aerobic conditions and it was almost (51%) in anaerobic systems. The low removal of COD in the anaerobic reactor may be due to the high concentration of anionic surfactant in the inlet (43.5 mg/L) and poor removal of colloidal organic compounds. COD removal was reported to be higher than (89%) in the combined aerobic-anaerobic treatment system, which was similar to aerobic treatment. Domestic gray water Methanogens was (32%) for anaerobic systems and (25%) for anaerobic-aerobic systems, which produced little energy. Thus, anaerobic pretreatment is not practical, and aerobic gray water treatment is preferred \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003eA biological treatment system and a chemical oxidation system were used to conduct this system, as shown in the (Figs.\u0026nbsp;1 and 2\u003cb\u003e)\u003c/b\u003e. In the biological treatment system, a plastic container with a volume of 8 liters was used, (60%) of which was filled with sludge from the extensive aeration wastewater treatment plant. (Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) presents the gray wastewater compounds and Quality characteristics. The SBR reactor started working for one month to adapt the sludge to the gray water. The SBR reactor included six phases filling, anaerobic, aeration, anoxic, settling, and discharge. The MLSS amount after one month in the aeration part was 2800 mg/l and SVI was 95 ml/g, which is suitable for biological treatment. Aeration was done with an aquarium pump to the extent that dissolved oxygen in the aerobic system was above 5 mg/liter. Two UV lamps with a power of 15 watts are placed on the ceiling of a glass box with dimensions of 80x20x15. It was covered with aluminum foil so it did not have contact with water for radiation. The distance between the lamps and the water was 5 cm. The environment temperature varied between 25 and 35\u0026deg;C. The stirrer speed in the SBR unit was about 50 RPM. To increase the biological treatment efficiency, granular activated carbon Norit GAC 830 was used with an effective size of 0.9 mm, uniformity coefficient of 1.7, and an effective surface area of 975 m2/g. Gray water samples were kept at 4\u0026deg;C and tested up to 48 hours.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003egray water compounds\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\u003eCompound\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnit in 20 liters of water\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003elaundry detergent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMeat extract\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCake flour\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoap Body\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.01\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\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\u003egray water characterization\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCompound\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\u003eValue\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\u003eMg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\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\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e600\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\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTSS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTDS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e800\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCl\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTKN\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMg/l\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e "},{"header":"Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003eCOD removal rate with aeration time in the SBR system\u003c/h2\u003e\n \u003cp\u003eThe removal rate of COD and BOD\u003csub\u003e5\u003c/sub\u003e of synthetic gray water with COD\u0026thinsp;=\u0026thinsp;600 mg/l and BOD5\u0026thinsp;=\u0026thinsp;270 mg/l with a volume of 3 liters for 24 hours in an SBR reactor was investigated in filling, anaerobic, aeration, anoxic, and settling phases. The aerobic and anaerobic stages were continued for 6 and 12 hours to determine the performance of the system at different times for optimization, as shown in (Fig. 3\u003cstrong\u003e)\u003c/strong\u003e. COD removal efficiency in anaerobic, aeration, and total phases was 46, 34, and 73%, respectively. BOD\u003csub\u003e5\u003c/sub\u003e removal in anaerobic, aerobic, and total stages was measured at 65.5, 52.5, and 85% respectively. BOD\u003csub\u003e5\u003c/sub\u003e of gray water after SBR was reduced from 270 to 40 and COD from 600 to 162 mg/L. During the first two and four hours of the anaerobic and aeration phases, COD and BOD\u003csub\u003e5\u003c/sub\u003e were removed at the highest rate, while the removal of organic matter decreased over time, so the duration of anaerobic and aeration more than 2 and 4 hours will not be useful in pollutant removal. The high removal efficiency was not observed due to the high concentration of detergents and the low concentration of biodegradable compounds, so the BOD/COD ratio after SBR was 0.25. Thus, biological treatment alone cannot remove the organic compounds of this type of gray water for discharge into the environment.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003ePhosphorus and nitrogen removal rate in SBR system\u003c/h2\u003e\n \u003cp\u003eGray water with phosphorus and nitrogen content of 4 and 15.1 mg/L entered the SBR reactor in a volume of 3 liters and followed the steps of filling, anaerobic, aeration, anoxic, settling, and discharge. (Fig.\u0026nbsp;4\u003cstrong\u003e)\u003c/strong\u003e illustrates that the phosphate concentration in the water increases over time in the anaerobic phase up to 2 hours, but then remains constant until 6 hours. In other words, soluble phosphorus can increase up to two hours in anaerobic conditions, and longer times have no impact on phosphorus removal. Ammonia nitrogen and phosphate concentrations were reduced from 15.1 and 13.2 to 5.26 and 0.7 mg/liter after 5 hours of aeration. Increasing the aeration time up to 12 hours showed little impact on ammonia nitrogen removal. Thus, the anaerobic and aeration time of 2 and 5 hours is sufficient and optimal to remove a maximum of 82.5% of phosphorus and 65% of ammonia nitrogen.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003eThe effect of using granular activated carbon in pollution removal\u003c/h2\u003e\n \u003cp\u003eBased on the optimal conditions of the previous stages, the duration of filling, anaerobic, aerobic, anoxic, and settling phases was 2 minutes, 2, 4, 1, and 4 hours, respectively. In the SBR reactor, granular activated carbon was added from 250 to 1250 mg/liter, respectively, as suggested by previous studies in the aeration part. As shown in (Fig.\u0026nbsp;5\u003cstrong\u003e)\u003c/strong\u003e, the COD, NH\u003csub\u003e4\u003c/sub\u003e, and PO\u003csub\u003e4\u003c/sub\u003e removal efficiency increases slightly as the granular activated carbon concentration increases and has almost no effect.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eThe effect of pH and residence time on gray water COD removal in the UV/H2O2 process\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eSynthetic gray water after biological treatment with COD\u0026thinsp;=\u0026thinsp;170 mg/l was subjected to UV/H2O2 chemical oxidation. COD removal rate regarding residence time and pH can be seen in (Fig.\u0026nbsp;6\u003cstrong\u003e).\u003c/strong\u003e The COD removal efficiency at a fixed contact time of 3 hours and pH of 2, 4, 6, 8, 10, 12, and 14 was observed to be 65, 71, 73, 78, 81, 62, and 49%, respectively. At constant residence time, the removal efficiency of organic compounds increased slightly with increasing pH.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003eOptimal dose of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e to remove organic pollution\u003c/h2\u003e\n \u003cp\u003eThe gray water discharged from the SBR with a COD of 170 mg/L was subjected to UV/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e chemical oxidation. According to the results of the previous stage, the pH and irradiation time were fixed at 10 and 3 hours, respectively. Based on (Fig. 7\u003cstrong\u003e)\u003c/strong\u003e, in the combined system with the dose of 0, 3.5, 5, 7, 12, 15, and 20 mg/L H2O2, the output COD values were measured at 170, 90, 78, 65, 56, 56, and 56 mg/L.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eThe effect of chemical oxidation before and after biological treatment\u003c/h2\u003e\n \u003cp\u003eIn the optimal conditions of SBR and the chemical oxidation process, obtained from the previous stages, the gray wastewater first goes through UV/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e chemical oxidation and then enters the SBR reactor. COD, NH\u003csub\u003e4\u003c/sub\u003e, and PO\u003csub\u003e4\u003c/sub\u003e in the output are 18, 5.25, and 0.72 mg/liter, respectively. As shown in (Fig. 8\u003cstrong\u003e)\u003c/strong\u003e, the COD removal efficiency is (97%) if the chemical oxidation process is performed before biological treatment. It is (6%) more than before, but the efficiency of phosphorus and nitrogen removal did not change compared to before.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eCOD and BOD\u003csub\u003e5\u003c/sub\u003e were removed with the highest rates during the first two and four hours of the anaerobic and aeration phases, while the removal of organic matter decreased over time, so the duration of anaerobic and aeration more than 2 and 4 hours will not be useful in pollutant removal. Given the high concentration of detergents in gray water and the low concentration of biodegradable compounds, high removal efficiency was not observed so the ratio of BOD/COD after SBR was 0.25. Thus, biological treatment alone cannot remove organic compounds to discharge into the environment. Gray water with phosphorus and nitrogen content of 4 and 15.1 mg/L entered the SBR reactor in a volume of 3 liters and followed the steps of filling, anaerobic, aeration, anoxic, settling, and discharge. Polyphosphate-accumulating organisms (PAOs) grow faster in anaerobic conditions and convert phosphorus into polyphosphate \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Aerobic processes alone cannot remove total phosphorus. To remove all phosphorus from the system, the anaerobic process should release it as polyphosphate \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Polyphosphate is removed faster due to the presence of nitrate as an electron acceptor during the aerobic phase \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Thus, it is useful to use an anaerobic unit to remove phosphorus before aeration. Soluble phosphorus can increase up to two hours in anaerobic conditions, and longer times have no impact on phosphorus removal. Nitrification occurs during the aeration process, which reduces ammonia nitrogen.\u003c/p\u003e \u003cp\u003eAmmonia nitrogen and phosphate concentrations were reduced from 15.1 and 13.2 to 5.26 and 0.7 mg/liter, respectively, after 5 hours of aeration. Increasing the aeration time up to 12 hours showed little impact on ammonia nitrogen removal. It does not help to remove nitrogen and phosphorus. Thus, the anaerobic and aeration times of 2 and 5 hours, respectively, are optimal to remove a maximum of (82.5%) of phosphorus and (65%) of ammonia nitrogen. Based on the optimal conditions, the time of filling, anaerobic, aerobic, anoxic, and settling phases were obtained at 2 minutes, 2, 4, 1, and 4 hours, respectively. Laminate in gray water treatment showed better nitrification than SBR with a residence time of 2.5 days. During the residence time of 2.5 days, the concentration of phosphate remained fixed in the anoxic phase and decreased slightly in the aeration phase. The final phosphate concentration was observed at 3 mg/l \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Fountoulakis showed that COD/BOD must be less than 2 mg/l to remove phosphorus. If there are fatty acids resulting from anaerobic decomposition, phosphorus will not be removed \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAnother study in 2016 revealed the duration of aeration and anaerobic should be changed to remove phosphorus \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Studies have shown that the surfactant in gray water is toxic to anaerobic bacteria \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Other studies have reported that LAS reduces the activity of anaerobic bacteria \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e and surfactants stop the methanogenic phase \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Granular activated carbon was used to increase the removal efficiency of organic compounds, nitrogen, and phosphorus in SBR, but a very small positive impact was observed. Previous studies have recommended the use of granular activated carbon in the removal of COD, NH4, and PO4 in the biological treatment of slaughterhouse wastewater \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Moving forward, further investigations into optimizing the application parameters of activated carbon, as well as exploration of alternative treatment strategies, may be warranted to address the persistent challenge of pollutant removal in gray water treatment systems.\u003c/p\u003e \u003cp\u003eCOD removal efficiency decreases at pH values greater than 10 after biological treatment in the chemical oxidation process. This is because H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e is converted to H2O and O2 at high pH and a small amount of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e remains in the treated water. The effect of pH on the removal rate of organic compounds is negligible at pH values below 10. The effect of pH on the removal of organic compounds decreases in the presence of carbonate or bicarbonate, and more than 300 mg/L based on CaCo\u003csub\u003e3\u003c/sub\u003e negatively affects chemical oxidation \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Based on \u003cb\u003eFig.\u0026nbsp;5\u003c/b\u003e, the COD removal efficiency was measured at (91%) at a residence time of 3 hours. Results obtained by Tokhanen in 1997 were different. In this study, acidic conditions with a residence time of 2 hours were more effective \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. The HCo\u003csub\u003e3\u003c/sub\u003e and CO\u003csub\u003e3\u003c/sub\u003e formation in high alkalinity conditions showed a negative impact on chemical oxidation. UV/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e reduces pH values due to the conversion of organic matter into mineral acids and carbon dioxide \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe concentration of produced hydroxyl decreases and the removal power of organic compounds decreases with an excessive increase in H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e \u003csup\u003e25\u003c/sup\u003e. The COD removal rate in chemical oxidation and combined system with SBR was (67% and 90.6%), respectively. Irradiation of water or wastewater containing H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e with UV rays produces hydroxyl radicals. UV rays break down H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e into hydroxyl radicals. Organic compounds are easily oxidized by hydroxyl radicals \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. Hassanshahi removed (92.1%) of COD using a combined UV/H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e/O\u003csub\u003e3\u003c/sub\u003e system with a dose of 200 mg/L H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, an O\u003csub\u003e3\u003c/sub\u003e concentration of 150 mg/L, and a residence time of 4 hours at pH\u0026thinsp;=\u0026thinsp;68 \u003csup\u003e27\u003c/sup\u003e. The use of chemical oxidation as a pre-treatment of the SBR system increased the COD removal efficiency by (6%). Its reason may be the breakdown of non-degradable compounds and the increase of the BOD/COD ratio due to UV rays and the chemical oxidation process \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eSaeid govahi : original text of research and pilot constructionEhsan Derikvand: text of the original research and pilot constructionSaeb Khoshnavaz: research methodMohsen Soleimani Babrasad: analysis of the resultsIman Parseh: research background\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eS. Tsoumachidou, T. Velegraki, A. Antoniadis, I. Poulios, Journal of environmental management 2017, 195, 232.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eK. Carden, N. Armitage, K. Winter, O. Sichone, U. Rivett, J. Kahonde, Water SA 2007, 33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eN. Rodda, L. Salukazana, S. Jackson, M. T. Smith, Physics and Chemistry of the Earth, Parts A/B/C 2011, 36, 1051.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eB. Pittock, Water: Journal of the Australian Water Association 2007, 34, 42.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ea)E. Eriksson, K. Auffarth, A. M. Eilersen, M. Henze, A. Ledin, \u003cem\u003eWater Sa\u003c/em\u003e 2003, 29, 135; b)V. Lazarova, S. Hills, R. Birks, \u003cem\u003eWater Science and Technology: Water Supply\u003c/em\u003e 2003, 3, 69.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eF. G\u0026uuml;nther, Ecological Engineering 2000, 15, 139.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ea)B. Jefferson, J. E. Burgess, A. Pichon, J. Harkness, S. J. Judd, \u003cem\u003eWater research\u003c/em\u003e 2001, 35, 2702; b)P. Jeffrey, B. 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Green, Water research 1999, 33, 2315.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eN. Hassanshahi, A. Karimi-Jashni, Ecotoxicology and environmental safety 2018, 161, 683.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. A. Zazouli, Z. Yousefi, E. Babanezhad, R. A. Mohammadpour, A. Ala, Environmental Health Engineering And Management Journal 2024, 0.\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":"Biological, Chemical oxidation, Gray water, Treatment","lastPublishedDoi":"10.21203/rs.3.rs-4021079/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4021079/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the treatment of gray water with high detergent content through a combination system of sequential batch reactor (SBR) and UV/H2O2 chemical oxidation. Preliminary analysis showed COD, BOD, TP and TKN levels of 600, 200, 4 and 15 mg/L respectively. As a result of SBR treatment, BOD5 decreased from 270 to 40 mg/L and COD from 600 to 162 mg/L. Activated carbon powder showed the least effect on pollutant removal efficiency. The optimal concentration of H2O2 was 12 mg/L and the duration of 3 hours for chemical oxidation was determined. The duration of aerobic and anaerobic SBR more than 4 and 2 hours, respectively, had negligible effects on pollutant removal. The combined SBR and chemical oxidation system achieved removal efficiencies of 90.6, 85, 82.5, and 65% for COD, BOD, TP, and TKN, respectively. Placing chemical oxidation before biological treatment increased organic compound removal by 6% because chemical oxidation increased biodegradable compounds. In addition, using an anaerobic unit to remove phosphorus before aeration was effective, more than two hours of anaerobic treatment had no effect on the removal of dissolved phosphorus.\u003c/p\u003e","manuscriptTitle":"Optimization of SBR Biological Treatment System and Advanced Oxidation for Non-Biodegradable Gray Water Treatment","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-25 19:56:31","doi":"10.21203/rs.3.rs-4021079/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":"fbd1a9e5-b5ce-4229-b557-f083c9bfa146","owner":[],"postedDate":"March 25th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":29825951,"name":"Biological sciences/Biological techniques"},{"id":29825952,"name":"Earth and environmental sciences/Environmental sciences"},{"id":29825953,"name":"Physical sciences/Energy science and technology"}],"tags":[],"updatedAt":"2024-04-01T06:08:04+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-25 19:56:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4021079","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4021079","identity":"rs-4021079","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}