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Yueping Ren - One of the best experts on this subject based on the ideXlab platform.

  • impacts of Sludge Retention Time on Sludge characteristics and membrane fouling in a submerged osmotic membrane bioreactor
    Bioresource Technology, 2014
    Co-Authors: Xinhua Wang, Yao Chen, Bo Yuan, Yueping Ren
    Abstract:

    Anaerobic–oxic membrane bioreactor (AOMBR) has been proposed as a highly effective method in municipal and industrial wastewater treatment. In this study, according to the sewage treatment system in a campus, long-term experiments were conducted to assess the impacts of the Sludge Retention Time (SRT) on Sludge characteristics and membrane fouling, and the Sludge parameters include biomass concentration, particle size distribution, extracellular polymeric substances (EPS), soluble microbial products (SMPs), and specific resistance to filtration (SRF). Our results clearly demonstrated that SRT was one of the most important factors influencing Sludge characteristics, and different Sludge characteristics resulted in different membrane fouling degrees. A better treatment and filtration performances were observed at the SRT of 30 days compared to two SRTs of 10 and 90 days. Among these parameters, SMP had the most significant correlation with the membrane fouling rate (dTMP/dt), and it had a negative impact on membrane filtration performance. The impact of SRT on membrane fouling process was discussed further by filtration models. At 10 days SRT, the complete-standard blocking model curve had a comparatively higher goodness-of-fit with the fouling process, and at 30 and 90 days SRT, the cake-standard blocking model curve had a relatively higher goodness-of-fit with respective fouling process.

  • impacts of Sludge Retention Time on Sludge characteristics and membrane fouling in a submerged osmotic membrane bioreactor
    Bioresource Technology, 2014
    Co-Authors: Xinhua Wang, Yao Chen, Bo Yuan, Yueping Ren
    Abstract:

    Abstract Sludge Retention Time (SRT) is a feasible method to alleviate the salt accumulation in the osmotic membrane bioreactor (OMBR) by discharging the waste activated Sludge. In this study, effects of SRT on Sludge characteristics and membrane fouling were investigated using a submerged OMBR under two SRTs of 10 and 15 d. The results showed that the lower SRT was helpful for alleviating the salt accumulation and flux decline. Besides that, the removal of NH3-N was significantly influenced by SRT. SRT also had a strong effect on soluble microbial products (SMP) and microbial activity due to the variation of salinity. Microbial diversity analysis indicated that the high salinity environment in the OMBR significantly affected the microbial communities. The flux decline in the OMBR was mainly attributed to the reduced driving force resulting from the salt accumulation, and the reversible fouling was the dominant forward osmosis (FO) membrane fouling in the OMBR.

  • influences of Sludge Retention Time on the performance of submerged membrane bioreactors with the addition of iron ion
    Desalination, 2012
    Co-Authors: Xinhua Wang, Yueping Ren, Kang Chen, Jiejie Qian, Zhaozhe Hua
    Abstract:

    Abstract A bench-scale submerged membrane bioreactor (MBR) treating synthetic wastewater with FeCl3 dose of 15 mg/L was operated under different Sludge Retention Times (SRTs), i.e. 10, 20 and 30 d, in order to evaluate the impacts of SRT on the performance of MBRs with the addition of FeCl3. The results showed that the effluent quality was slightly influenced by SRT, while membrane fouling was effectively mitigated by lengthening SRT under the condition of FeCl3 adding. The concentration of soluble microbial products (SMP) significantly decreased as SRT extended from 10 to 30 d, which correlated well with the variation of membrane fouling. SMP played a more important role in membrane fouling in this study compared to other Sludge properties. Fe accumulated in the MBR as SRT prolonged, and the accumulation of Fe enhanced flocculation and resulted in the decrease of MLVSS/MLSS ratio and the increase of particle size. The accumulated Fe in mixed liquor was mainly located in bound extracellular polymeric substances (BEPS). It is suggested that the negatively functional groups such as polysaccharide in SMP were adsorbed by the bridging effects of iron ion, thus leading to the reduction of SMP and increase of BEPS at longer SRT.

Xinhua Wang - One of the best experts on this subject based on the ideXlab platform.

  • impacts of Sludge Retention Time on Sludge characteristics and membrane fouling in a submerged osmotic membrane bioreactor
    Bioresource Technology, 2014
    Co-Authors: Xinhua Wang, Yao Chen, Bo Yuan, Yueping Ren
    Abstract:

    Anaerobic–oxic membrane bioreactor (AOMBR) has been proposed as a highly effective method in municipal and industrial wastewater treatment. In this study, according to the sewage treatment system in a campus, long-term experiments were conducted to assess the impacts of the Sludge Retention Time (SRT) on Sludge characteristics and membrane fouling, and the Sludge parameters include biomass concentration, particle size distribution, extracellular polymeric substances (EPS), soluble microbial products (SMPs), and specific resistance to filtration (SRF). Our results clearly demonstrated that SRT was one of the most important factors influencing Sludge characteristics, and different Sludge characteristics resulted in different membrane fouling degrees. A better treatment and filtration performances were observed at the SRT of 30 days compared to two SRTs of 10 and 90 days. Among these parameters, SMP had the most significant correlation with the membrane fouling rate (dTMP/dt), and it had a negative impact on membrane filtration performance. The impact of SRT on membrane fouling process was discussed further by filtration models. At 10 days SRT, the complete-standard blocking model curve had a comparatively higher goodness-of-fit with the fouling process, and at 30 and 90 days SRT, the cake-standard blocking model curve had a relatively higher goodness-of-fit with respective fouling process.

  • impacts of Sludge Retention Time on Sludge characteristics and membrane fouling in a submerged osmotic membrane bioreactor
    Bioresource Technology, 2014
    Co-Authors: Xinhua Wang, Yao Chen, Bo Yuan, Yueping Ren
    Abstract:

    Abstract Sludge Retention Time (SRT) is a feasible method to alleviate the salt accumulation in the osmotic membrane bioreactor (OMBR) by discharging the waste activated Sludge. In this study, effects of SRT on Sludge characteristics and membrane fouling were investigated using a submerged OMBR under two SRTs of 10 and 15 d. The results showed that the lower SRT was helpful for alleviating the salt accumulation and flux decline. Besides that, the removal of NH3-N was significantly influenced by SRT. SRT also had a strong effect on soluble microbial products (SMP) and microbial activity due to the variation of salinity. Microbial diversity analysis indicated that the high salinity environment in the OMBR significantly affected the microbial communities. The flux decline in the OMBR was mainly attributed to the reduced driving force resulting from the salt accumulation, and the reversible fouling was the dominant forward osmosis (FO) membrane fouling in the OMBR.

  • influences of Sludge Retention Time on the performance of submerged membrane bioreactors with the addition of iron ion
    Desalination, 2012
    Co-Authors: Xinhua Wang, Yueping Ren, Kang Chen, Jiejie Qian, Zhaozhe Hua
    Abstract:

    Abstract A bench-scale submerged membrane bioreactor (MBR) treating synthetic wastewater with FeCl3 dose of 15 mg/L was operated under different Sludge Retention Times (SRTs), i.e. 10, 20 and 30 d, in order to evaluate the impacts of SRT on the performance of MBRs with the addition of FeCl3. The results showed that the effluent quality was slightly influenced by SRT, while membrane fouling was effectively mitigated by lengthening SRT under the condition of FeCl3 adding. The concentration of soluble microbial products (SMP) significantly decreased as SRT extended from 10 to 30 d, which correlated well with the variation of membrane fouling. SMP played a more important role in membrane fouling in this study compared to other Sludge properties. Fe accumulated in the MBR as SRT prolonged, and the accumulation of Fe enhanced flocculation and resulted in the decrease of MLVSS/MLSS ratio and the increase of particle size. The accumulated Fe in mixed liquor was mainly located in bound extracellular polymeric substances (BEPS). It is suggested that the negatively functional groups such as polysaccharide in SMP were adsorbed by the bridging effects of iron ion, thus leading to the reduction of SMP and increase of BEPS at longer SRT.

  • impacts of Sludge Retention Time on the performance of submerged membrane bioreactor with the addition of calcium ion
    Separation and Purification Technology, 2011
    Co-Authors: Kang Chen, Xinhua Wang, Jiejie Qian, Xiaolan Xiao
    Abstract:

    Abstract A laboratory-scale submerged membrane bioreactor (MBR) for the treatment of synthetic wastewater containing 200 mg/L Ca 2+ was operated under Sludge Retention Time (SRT) of 10, 20 and 30 d in this study in order to verify the impacts of SRT on the performance of MBR with the addition of Ca 2+ . The results showed that the effluent quality was slightly influenced by SRT, while membrane fouling was effectively mitigated by extending SRT with the addition of Ca 2+ due to the decline of fouling layer resistance. The concentration of soluble microbial products (SMP) significantly decreased as SRT prolonged from 10 to 30 d, which correlated well with the variation of membrane fouling. SMP and particle size played a more important role in membrane fouling in this study compared to other Sludge properties. The Ca 2+ accumulated in MBR as the SRT extended, and the accumulation of Ca 2+ enhanced bioflocculation and resulted in the decrease of MLVSS/MLSS ratio and the increase of the average particle size. The accumulated Ca 2+ in mixed liquor was mainly located in bound extracellular polymeric substances (BEPS). It might be indicated that the negatively functional groups such as polysaccharide in SMP were adsorbed to BEPS by the bridging effects of Ca 2+ , which led to the reduction of SMP and increase of BEPS at longer SRT.

Alfieri Pollice - One of the best experts on this subject based on the ideXlab platform.

  • influence of Sludge Retention Time on biomass characteristics and cleaning requirements in a membrane bioreactor for municipal wastewater treatment
    Desalination, 2009
    Co-Authors: Giuseppe Laera, Alfieri Pollice, D Saturno, C Giordano, Roberto Sandulli
    Abstract:

    Abstract The study is aimed at defining possible correlations between Sludge Retention Time (SRT), biomass growth, biomass activity and membrane cleaning requirements in a submerged membrane bioreactor (MBR). For the experimental campaign, a lab-scale MBR was continuously fed on pre-settled municipal wastewater and operated to obtain complete nitrification. Volumetric loading rate of 1.2 gCOD L − 1 d − 1 was maintained by fixing the permeate flux and diluting the influent wastewater as required. Experimental runs were performed adopting SRT of 20, 40, 60 and 80 days. Results were integrated with data from a previous experiment with complete Sludge Retention. A significant correlation between SRT and organic loading rate has been observed. Results of the respirometric measurements suggested that the biomass activity is weakly affected by the Sludge age. Membrane cleaning requirements also appear to be scarcely dependent on SRT and on the average membrane cleaning was required about every 2 months. Further investigation of the Sludge physical properties indicate that the capillary suction Time can be considered as a suitable early warning parameter for the cleaning schedules. The findings allow the conclusion that SRT longer than 40 days could be considered for reliable operation of MBRs for municipal wastewater treatment.

  • effects of Sludge Retention Time on the performance of a membrane bioreactor treating municipal sewage
    Journal of Membrane Science, 2008
    Co-Authors: Alfieri Pollice, Giuseppe Laera, D Saturno, C Giordano
    Abstract:

    Abstract The performance of a bench scale membrane bioreactor (MBR) fed on real municipal wastewater was monitored over the long-term in order to investigate optimal operating conditions in terms of process parameters. The experimental MBR was operated for a total period of 4 years under the same conditions except for the Sludge Retention Time (SRT). Five tests were run after fresh start-ups, and different SRT ranging between 20 days and complete Retention were adopted. This paper focuses on the SRT influence on parameters related to Sludge filterability, membrane cleaning and biological activity. The average biomass concentration under steady state conditions increased for increasing SRT with a logarithmic function. In order to evaluate the Sludge filterability, the capillary suction Time (CST) and Sludge resistance to filtration (SRF) were monitored over Time showing decreasing trends during the transient phase and average steady state values comparable with those reported for conventional activated Sludge. The CST and SRF steady state values were minimized for SRT in the range 40–80 days. The viscosity increased with increasing SRT and appeared to be related to the suspended solids content. The membrane cleaning frequency decreased towards 1 cleaning every 2 months as the system approached the steady state. The experimental data suggested the adoption of the CST for early warning of the cleaning needs. The respirometric tests showed that the membrane bioreactor could be operated at the higher SRT without drawbacks on the biodegradation activities.

  • optimal Sludge Retention Time for a bench scale mbr treating municipal sewage
    Water Science and Technology, 2008
    Co-Authors: Alfieri Pollice, Giuseppe Laera, D Saturno, C Giordano, Roberto Sandulli
    Abstract:

    Membrane bioreactors allow for higher Sludge concentrations and improved degradation efficiencies with respect to conventional activated Sludge. However, in the current practice these systems are often operated under sub-optimal conditions, since so far no precise indications have yet been issued on the optimal operating conditions of MBR for municipal wastewater treatment. This paper reports some results of four years of operation of a bench scale membrane bioreactor where steady state conditions were investigated under different Sludge Retention Times. The whole experimental campaign was oriented towards the investigation of optimal process conditions in terms of COD removal and nitrification, biomass activity and growth, and Sludge characteristics. The membrane bioreactor treated real municipal sewage, and four different Sludge ages were tested (20, 40, 60, and 80 days) and compared with previous data on complete Sludge Retention. The results showed that the the biology of the system, as assessed by the oxygen uptake rate, is less affected than the Sludge physical parameters. In particular, although the growth yield was observed to dramatically drop for SRT higher than 80 days, the biological activity was maintained under all the tested conditions. These considerations suggest that high SRT are convenient in terms of limited excess Sludge production without losses of the treatment capacity. Physical characteristics such as the viscosity and the filterability appear to be negatively affected by prolonged Sludge Retention Times, but their values remain within the ranges normally reported for conventional activated Sludge.

  • influence of aeration and Sludge Retention Time on ammonium oxidation to nitrite and nitrate
    Water Research, 2002
    Co-Authors: Alfieri Pollice, Valter Tandoi, Carmela Lestingi
    Abstract:

    Partial nitrification to nitrite was reported to be technically feasible and economically favourable, especially when wastewater with high ammonium concentrations or low C/N ratios are treated. Nitritation can be obtained by selectively inhibiting nitrite oxidizing microrganisms through appropriate regulation of the system's pH, temperature, and Sludge Retention Time. In addition to already known methods, the work showed that aeration patterns may play a relevant role too. Nitrification tests were performed in two lab-scale reactors operated under continuous and intermittent aeration, respectively. In both plants, temperature was maintained at 32°C and pH was regulated at 7.2 by providing external buffer capacity when needed. The results showed that partial nitrification to nitrite was steadily obtained under oxygen limitation, independent of the Sludge age. Therefore, the aeration pattern is proposed as an alternative parameter to the Sludge Retention Time for controlling ammonium oxidation to nitrite.

Xavier Lefebvre - One of the best experts on this subject based on the ideXlab platform.

  • combined thermophilic aerobic process and conventional anaerobic digestion effect on Sludge biodegradation and methane production
    Bioresource Technology, 2010
    Co-Authors: Claire Dumas, Etienne Paul, Serge Perez, Xavier Lefebvre
    Abstract:

    Abstract The efficiency of hyper-thermophilic (65 °C) aerobic process coupled with a mesophilic (35 °C) digester was evaluated for the activated Sludge degradation and was compared to a conventional mesophilic digester. For two Sludge Retention Time (SRT), 21 and 42 days, the Chemical Oxygen Demand (COD) solubilisation and biodegradation processes, the methanisation yield and the aerobic oxidation were investigated during 180 days. The best results were obtained at SRT of 44 days; the COD removal yield was 30% higher with the Mesophilic Anaerobic Digestion/Thermophilic Aerobic Reactor (MAD–TAR) co-treatment. An increase of the Sludge intrinsic biodegradability is also observed (20–40%), showing that the unbiodegradable COD in mesophilic conditions becomes bioavailable. However, the methanisation yield was quite similar for both processes at a same SRT. Finally, such a process enables to divide by two the volume of digester with an equivalent efficiency.

  • Combined thermophilic aerobic process and conventional anaerobic digestion: effect on Sludge biodegradation and methane production
    Bioresource Technology, 2010
    Co-Authors: Claire Dumas, Etienne Paul, Serge Perez, Xavier Lefebvre
    Abstract:

    The efficiency of hyper-thermophilic (65 degrees Celsius) aerobic process coupled with a mesophilic (35 degrees Celsius) digester was evaluated for the activated Sludge degradation and was compared to a conventional mesophilic digester. For two Sludge Retention Time (SRT), 21 and 42 days, the Chemical Oxygen Demand (COD) solubilisation and biodegradation processes, the methanisation yield and the aerobic oxidation were investigated during 180 days. The best results were obtained at SRT of 44 days; the COD removal yield was 30% higher with the Mesophilic Anaerobic Digestion/Thermophilic Aerobic Reactor (MAD-TAR) co-treatment. An increase of the Sludge intrinsic biodegradability is also observed (20-40%), showing that the unbiodegradable COD in mesophilic conditions becomes bioavailable. However, the methanisation yield was quite similar for both processes at a same SRT. Finally, such a process enables to divide by two the volume of digester with an equivalent efficiency.

C Giordano - One of the best experts on this subject based on the ideXlab platform.

  • influence of Sludge Retention Time on biomass characteristics and cleaning requirements in a membrane bioreactor for municipal wastewater treatment
    Desalination, 2009
    Co-Authors: Giuseppe Laera, Alfieri Pollice, D Saturno, C Giordano, Roberto Sandulli
    Abstract:

    Abstract The study is aimed at defining possible correlations between Sludge Retention Time (SRT), biomass growth, biomass activity and membrane cleaning requirements in a submerged membrane bioreactor (MBR). For the experimental campaign, a lab-scale MBR was continuously fed on pre-settled municipal wastewater and operated to obtain complete nitrification. Volumetric loading rate of 1.2 gCOD L − 1 d − 1 was maintained by fixing the permeate flux and diluting the influent wastewater as required. Experimental runs were performed adopting SRT of 20, 40, 60 and 80 days. Results were integrated with data from a previous experiment with complete Sludge Retention. A significant correlation between SRT and organic loading rate has been observed. Results of the respirometric measurements suggested that the biomass activity is weakly affected by the Sludge age. Membrane cleaning requirements also appear to be scarcely dependent on SRT and on the average membrane cleaning was required about every 2 months. Further investigation of the Sludge physical properties indicate that the capillary suction Time can be considered as a suitable early warning parameter for the cleaning schedules. The findings allow the conclusion that SRT longer than 40 days could be considered for reliable operation of MBRs for municipal wastewater treatment.

  • effects of Sludge Retention Time on the performance of a membrane bioreactor treating municipal sewage
    Journal of Membrane Science, 2008
    Co-Authors: Alfieri Pollice, Giuseppe Laera, D Saturno, C Giordano
    Abstract:

    Abstract The performance of a bench scale membrane bioreactor (MBR) fed on real municipal wastewater was monitored over the long-term in order to investigate optimal operating conditions in terms of process parameters. The experimental MBR was operated for a total period of 4 years under the same conditions except for the Sludge Retention Time (SRT). Five tests were run after fresh start-ups, and different SRT ranging between 20 days and complete Retention were adopted. This paper focuses on the SRT influence on parameters related to Sludge filterability, membrane cleaning and biological activity. The average biomass concentration under steady state conditions increased for increasing SRT with a logarithmic function. In order to evaluate the Sludge filterability, the capillary suction Time (CST) and Sludge resistance to filtration (SRF) were monitored over Time showing decreasing trends during the transient phase and average steady state values comparable with those reported for conventional activated Sludge. The CST and SRF steady state values were minimized for SRT in the range 40–80 days. The viscosity increased with increasing SRT and appeared to be related to the suspended solids content. The membrane cleaning frequency decreased towards 1 cleaning every 2 months as the system approached the steady state. The experimental data suggested the adoption of the CST for early warning of the cleaning needs. The respirometric tests showed that the membrane bioreactor could be operated at the higher SRT without drawbacks on the biodegradation activities.

  • optimal Sludge Retention Time for a bench scale mbr treating municipal sewage
    Water Science and Technology, 2008
    Co-Authors: Alfieri Pollice, Giuseppe Laera, D Saturno, C Giordano, Roberto Sandulli
    Abstract:

    Membrane bioreactors allow for higher Sludge concentrations and improved degradation efficiencies with respect to conventional activated Sludge. However, in the current practice these systems are often operated under sub-optimal conditions, since so far no precise indications have yet been issued on the optimal operating conditions of MBR for municipal wastewater treatment. This paper reports some results of four years of operation of a bench scale membrane bioreactor where steady state conditions were investigated under different Sludge Retention Times. The whole experimental campaign was oriented towards the investigation of optimal process conditions in terms of COD removal and nitrification, biomass activity and growth, and Sludge characteristics. The membrane bioreactor treated real municipal sewage, and four different Sludge ages were tested (20, 40, 60, and 80 days) and compared with previous data on complete Sludge Retention. The results showed that the the biology of the system, as assessed by the oxygen uptake rate, is less affected than the Sludge physical parameters. In particular, although the growth yield was observed to dramatically drop for SRT higher than 80 days, the biological activity was maintained under all the tested conditions. These considerations suggest that high SRT are convenient in terms of limited excess Sludge production without losses of the treatment capacity. Physical characteristics such as the viscosity and the filterability appear to be negatively affected by prolonged Sludge Retention Times, but their values remain within the ranges normally reported for conventional activated Sludge.