Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge
This is the first study that examines the effect of operating conditions on fouling of Membrane Bio-Reactors (MBRs), which treat municipal wastewater in field conditions, with specific regard to the controlled development of filamentous microorganisms (or filaments). The novelty of the present work...
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| Format: | Article |
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MDPI AG
2021-06-01
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| Series: | Membranes |
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| Online Access: | https://www.mdpi.com/2077-0375/11/7/490 |
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| author | Petros Gkotsis Dimitra Banti Anastasia Pritsa Manassis Mitrakas Petros Samaras Efrosini Peleka Anastasios Zouboulis |
| author_facet | Petros Gkotsis Dimitra Banti Anastasia Pritsa Manassis Mitrakas Petros Samaras Efrosini Peleka Anastasios Zouboulis |
| author_sort | Petros Gkotsis |
| collection | DOAJ |
| description | This is the first study that examines the effect of operating conditions on fouling of Membrane Bio-Reactors (MBRs), which treat municipal wastewater in field conditions, with specific regard to the controlled development of filamentous microorganisms (or filaments). The novelty of the present work is extended to minimize the dissolved oxygen (DO) in recirculated activated sludge for improving the process of denitrification. For this purpose, two pilot-scale MBRs were constructed and operated in parallel: (i) Filament-MBR, where an attempt was made to regulate the growth of filaments by adjustment of DO, the Food-to-Microorganisms (F/M) ratio and temperature, and (ii) Control-MBR, where a gentle stirring tank was employed for the purpose of zeroing the DO in the recycled sludge. Results showed that low temperature (<15 °C) slightly increased the number of filaments in the Filament-MBR which, in turn, decreased the Trans-Membrane Pressure (TMP). As the Soluble Microbial Products (SMP) and the colloids are considered to be the basic foulants of membranes in MBR systems, specific attention was directed to keep their concentration at low values in the mixed liquor. The low F/M ratio in the aeration tanks which preceded the membrane tank was achieved to keep the SMP proteins and carbohydrates at very low values in the mixed liquor, i.e., less than 6 mg/L. Moreover, as a result of the low recirculation rate (2.6∙Q<sub>in</sub>), good aggregation of the produced excess sludge was achieved, and low concentration of colloids with a size ≤50 nm (nearly the membranes’ pore size used for filtration/separation) was measured, accounted for maximum 15% of the total colloids. Additionally, the increase in filamentous population at the Filament-MBR contributed to the further reduction of colloids in the mixed liquor at 7.9%, contributing beneficially to the reduction of TMP and of membrane fouling. The diminishing of DO in the recirculated sludge improved denitrification, and resulted in lower concentrations of Ν-NO<sub>3</sub><sup>−</sup> and TN in the effluent of the Control-MBR. Furthermore, the recirculation rate of Q<sub>r</sub> = 2.6∙Q<sub>in</sub>, in comparison with Q<sub>r</sub> = 4.3∙Q<sub>in</sub>, resulted in improved performance regarding the removal of N-NH<sub>4</sub><sup>+</sup>. Finally, high organics removal and ammonium nitrification was observed in the effluent of both pilots, since COD and Ν-ΝH<sub>4</sub><sup>+</sup> concentrations were generally in the range of 10–25 mg/L and <0.1 mg/L, respectively. |
| first_indexed | 2024-03-10T09:56:36Z |
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| id | doaj.art-3abd81d0bf2e4e39af6f11537ae23923 |
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| issn | 2077-0375 |
| language | English |
| last_indexed | 2024-03-10T09:56:36Z |
| publishDate | 2021-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Membranes |
| spelling | doaj.art-3abd81d0bf2e4e39af6f11537ae239232023-11-22T02:18:10ZengMDPI AGMembranes2077-03752021-06-0111749010.3390/membranes11070490Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated SludgePetros Gkotsis0Dimitra Banti1Anastasia Pritsa2Manassis Mitrakas3Petros Samaras4Efrosini Peleka5Anastasios Zouboulis6Laboratory of Chemical and Environmental Technology, Department of Chemistry, Faculty of Sciences, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, GreeceLaboratory of Technologies of Environmental Protection and Utilization of Food By-Products, Department of Food Science and Technology, International Hellenic University, GR-57400 Thessaloniki, GreeceAnalytic Chemistry Laboratory, Department of Chemical Engineering, School of Engineering, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, GreeceAnalytic Chemistry Laboratory, Department of Chemical Engineering, School of Engineering, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, GreeceLaboratory of Technologies of Environmental Protection and Utilization of Food By-Products, Department of Food Science and Technology, International Hellenic University, GR-57400 Thessaloniki, GreeceLaboratory of Chemical and Environmental Technology, Department of Chemistry, Faculty of Sciences, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, GreeceLaboratory of Chemical and Environmental Technology, Department of Chemistry, Faculty of Sciences, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, GreeceThis is the first study that examines the effect of operating conditions on fouling of Membrane Bio-Reactors (MBRs), which treat municipal wastewater in field conditions, with specific regard to the controlled development of filamentous microorganisms (or filaments). The novelty of the present work is extended to minimize the dissolved oxygen (DO) in recirculated activated sludge for improving the process of denitrification. For this purpose, two pilot-scale MBRs were constructed and operated in parallel: (i) Filament-MBR, where an attempt was made to regulate the growth of filaments by adjustment of DO, the Food-to-Microorganisms (F/M) ratio and temperature, and (ii) Control-MBR, where a gentle stirring tank was employed for the purpose of zeroing the DO in the recycled sludge. Results showed that low temperature (<15 °C) slightly increased the number of filaments in the Filament-MBR which, in turn, decreased the Trans-Membrane Pressure (TMP). As the Soluble Microbial Products (SMP) and the colloids are considered to be the basic foulants of membranes in MBR systems, specific attention was directed to keep their concentration at low values in the mixed liquor. The low F/M ratio in the aeration tanks which preceded the membrane tank was achieved to keep the SMP proteins and carbohydrates at very low values in the mixed liquor, i.e., less than 6 mg/L. Moreover, as a result of the low recirculation rate (2.6∙Q<sub>in</sub>), good aggregation of the produced excess sludge was achieved, and low concentration of colloids with a size ≤50 nm (nearly the membranes’ pore size used for filtration/separation) was measured, accounted for maximum 15% of the total colloids. Additionally, the increase in filamentous population at the Filament-MBR contributed to the further reduction of colloids in the mixed liquor at 7.9%, contributing beneficially to the reduction of TMP and of membrane fouling. The diminishing of DO in the recirculated sludge improved denitrification, and resulted in lower concentrations of Ν-NO<sub>3</sub><sup>−</sup> and TN in the effluent of the Control-MBR. Furthermore, the recirculation rate of Q<sub>r</sub> = 2.6∙Q<sub>in</sub>, in comparison with Q<sub>r</sub> = 4.3∙Q<sub>in</sub>, resulted in improved performance regarding the removal of N-NH<sub>4</sub><sup>+</sup>. Finally, high organics removal and ammonium nitrification was observed in the effluent of both pilots, since COD and Ν-ΝH<sub>4</sub><sup>+</sup> concentrations were generally in the range of 10–25 mg/L and <0.1 mg/L, respectively.https://www.mdpi.com/2077-0375/11/7/490MBRmembrane foulingfilamentous microorganismsrecirculation ratedenitrification |
| spellingShingle | Petros Gkotsis Dimitra Banti Anastasia Pritsa Manassis Mitrakas Petros Samaras Efrosini Peleka Anastasios Zouboulis Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge Membranes MBR membrane fouling filamentous microorganisms recirculation rate denitrification |
| title | Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge |
| title_full | Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge |
| title_fullStr | Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge |
| title_full_unstemmed | Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge |
| title_short | Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs: Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge |
| title_sort | effect of operating conditions on membrane fouling in pilot scale mbrs filaments growth diminishing dissolved oxygen and recirculation rate of the activated sludge |
| topic | MBR membrane fouling filamentous microorganisms recirculation rate denitrification |
| url | https://www.mdpi.com/2077-0375/11/7/490 |
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