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Ensuring the effluent quality despite fluctuations in influent flow rate and organic load to municipal wastewater treatment plants is critical. This study investigated the performance of a membrane bioreactor (MBR) in handling hydraulic and organic loading shocks during wastewater treatment. The ability of the MBR to remove COD, BOD5, and turbidity from synthetic wastewater was evaluated at steady-state and after applying five levels of organic shock loads (1.5×-4×) and four levels of hydraulic shocks (1.2×-4.7×). Due to the short-term shock-loadings no discernible effect was observed on the mixed liquor suspended solids implying biological stability. The average COD removal in MBR exposed to organic and hydraulic shock loads was 93.8% and 94%, respectively, similar to average BOD5 removals of 94.4% and 93.6%. The membrane retained suspended particles well throughout the process. However, it became quickly fouled only by applying a strong hydraulic shock. The MBR guaranteed the quality of the effluent. [ABSTRACT FROM AUTHOR]

This study investigates the effectiveness of zeolite for controlling the membrane fouling in a hybrid membrane bioreactor. A control membrane bioreactor without zeolite (CMBR) and a hybrid MBR with zeolite were studied, which were called 4 g L–1 zeolite (Z4-MBR), 8 g L–1 zeolite (Z8-MBR) and 12 g L–1 zeolite (Z12-MBR) within long- and short-term filtration experiments. On average, the Z4-MBR, Z8-MBR and Z12-MBR reduced soluble microbial products (SMPC) by 18.96%, 42.11% and 19.44%, respectively. Furthermore, the ZMBR systems developed lower operational trans-membrane pressure (TMP), lower zeta potential, increased the relative hydrophilicity of sludge and enhanced the concentration of EPS. Reduced membrane fouling and ease of membrane operation are concluded from this study. [ABSTRACT FROM AUTHOR]

This study investigated the long-term filtration of mesh filter with the formed dynamic membrane in bioreactor. The trend of transmembrane pressure (TMP) variations highly corresponded to the thickness and compactness index of dynamic membrane. The dynamic membrane was fractionated by applying two cleaning protocols, that is, rinsing and chemical cleaning. The desorbed fraction, consisting of soluble microbial products (> 70%), provided a stickiness surface for formation of consecutive biomass layer which featured a high concentration of extracellular polymeric substances (> 75%). The chemical oxygen demand (COD) removal was 70%, 89%, and 92% for period of 0–26, 26–49, and 49–67 day, respectively, which indicated that further development of dynamic membrane increased the TMP without improvement in the effluent quality (TMP: 50–200 mbar, COD removal: 89%; TMP: 200–600 mbar, COD removal: 92%). The averageand TN removal was about 76% and 21%, respectively. The effluent turbidity fell less than 2 NTU after 26 days of filtration. [ABSTRACT FROM PUBLISHER]

Highlights: [•] To develop formation process of self-forming dynamic membrane on mesh filter. [•] To optimize imposed flux and aeration rate for self-forming dynamic membrane. [•] To evaluate efficiency of dynamic membrane bioreactor in removal of COD and TDS. [•] To investigate the preferable cleaning method for recovery of fouled mesh filter. [•] To characterize dominant chemical matter in dynamic membrane using FTIR analysis. [ABSTRACT FROM AUTHOR]

Abstract: This work investigates filtration performance of mesh filter bioreactor for synthetic municipal wastewater treatment. Critical flux is measured by flux stepping method and the effect of aeration rate on the critical flux is investigated. The long term monitoring of trans-filter pressure evolution at sub and super-critical fluxes is performed. The analysis of resistance is achieved by determination of resistances and microscopic observation of bio-cake. Cake resistance values vary from 78% to 92% of total filtration resistance for sub and super-critical fluxes. The effect of variations of specific aeration demands (SADm: 0.5–6m3/m2 h) on suspended solid of effluent, turbidity of filtrate, filtration resistance, and zeta potential of biomass is evaluated. The results show that filtrate quality is decreased when the aeration rate increases. It is attributed to stable formation of dynamic membrane. A rather clear filtrate, less than 18 NTU of turbidity, is obtained for SADm 0.5m3/m2 h. The results also show that the total filtration resistance of the sub-critical flux significantly decreases with increasing aeration intensity until SADm 2m3/m2 h and thereafter slightly decreases. It is also shown that the variations of zeta potential of biomass with aeration rate highly correspond to the alterations of filtration resistance. [Copyright &y& Elsevier]

Rheological characterization is of crucial importance in sludge management both in terms of biomass dewatering and stabilization properties and in terms of design parameters for sludge handling operations. The mixed liquor suspended solid (MLSS) and coagulant concentration have a significant influence on biomass properties in biological wastewater treatment systems and in particular in membrane bioreactors (MBRs). In this work the rheological behavior of the biomass in a MBR operated under different MLSS was studied. The range of MLSS in the bench scale MBR was 3800 mg/l to 15200 mg/l. The rheological properties were measured over time and the apparent viscosity was correlated with the concentration of suspended solids under steady-state conditions. Furthermore, a correlation was obtained between sludge viscosity and permeate flux. Results showed that viscosity of activated sludge affects the membrane fouling tendency in an exponential relation between viscosity and fouling in the investigated range in membrane bioreactor. Also coagulants cause reduction of activated sludge viscosity and hence membrane fouling. [ABSTRACT FROM AUTHOR]