Linking hydrolytic activities to variables influencing a submerged membrane bioreactor (MBR) treating urban wastewater under real operating conditions

The objective of this research was to study hospital wastewater treatment using a submerged membrane bioreactor (SMBR). The lab scale unit of SMBR with a working volume of 20 liters was operated at a hydraulic retention time of 0.416 day and 0.208 day at F/M ratio of 0.18 day–1 and 0.29 day–1. The operating conditions were set up to provide good biological treatment without sludge extraction, and two different permeate flux values were studied. The performance of membrane was studied by monitoring the variation of transmenbrane pressure (TMP) during filtration runs. The efficiency of MBR was investigated according to the daily measurements of pH, dissolved oxygen and temperature. The COD, BOD5, NH4+–N, TKN, color, turbidity, SS and Escherichia coli (E.coli) in influent and effluent were analyzed. Membrane fouling intensity occurred slowly when the system operated with flux at 10 L/h/m2 and 20 L/h/m2, which induced high TMP at the initial period of filtration. The fouling rate was at about 0.3022 mbar/day for the permeation of flux at 10 L /h/m2. The fouling rate still remained at 0.2774 mbar/day for 20 L/h/m2. The results showed the great effect of membrane use for total biomass retention and the removal rate of COD, BOD5 and E.coli were over 90%. The characteristics of sludge in SMBR showed healthy floc formations with good settling. Although the ratio of MLVSS/MLSS was lower than the normal range (about 0.2), it was found that the average values of COD and NH4+–N in permeate were lower than 2–80 mg/L and 0.05–6.755 mg/L while the value of turbidity was also less than 3 NTU.

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Characterization of sludge structure and activity in submerged membrane bioreactor

Water Science & Technology ◽

10.2166/wst.2005.0717 ◽

2005 ◽

Vol 52 (10-11) ◽

pp. 401-408 ◽

Cited By ~ 33

Author(s):

M. Spérandio ◽

A. Masse ◽

M.C. Espinosa-Bouchot ◽

C. Cabassud

Keyword(s):

Activated Sludge ◽

Organic Compounds ◽

Membrane Bioreactor ◽

Operating Conditions ◽

Second Phase ◽

Submerged Membrane Bioreactor ◽

Half Saturation Constant ◽

Significant Difference ◽

Excess Substrate ◽

Biomass Activity

Sludge characteristics of a submerged membrane bioreactor (MBR) and an activated sludge process (AS) were compared, during a first phase at the same operating conditions (low MLSS and conventional SRT) and in a second phase with a high sludge retention time (SRT) in the membrane bioreactor. During the first phase, a bimodal flocs size distribution was observed in the MBR with simultaneously a macro-flocs population (240μm) bigger than the flocs of activated sludge due to the absence of recirculating pump, and also more microflocs (1 to 15μm) and free suspended cells retained by the membrane. It is shown that the membrane leads to an accumulation of proteins and polysaccharides in the sludge supernatant which is probably responsible for the high fouling propensity of the sludge during the starting period of MBR. These compounds are partially degraded after 50 to 60 days of operation. In the first phase respirometric experiments didn't demonstrate a significant difference in the maximal removal rates of either MBR or AS biomass (with excess substrate), except in the dynamic period during which the membrane retention gave an advantage by increasing the biomass activity. On the other hand, the respirometry shows that the half saturation constant for nitrification was significantly higher in the MBR process, suggesting higher substrate transfer limitation. During the last phase, it is shown that an increase of SRT from 9 to 106 days leads to a diminution of average macro-flocs size in the MBR from about 240 to 70μm. With the SRT increase, modification in the organic compounds is also observed (proteins, polysaccharides and COD) in the sludge supernatant. Increasing the SRT from 9 to 40 days seems to slightly reduce the level of organic compounds (probable biodegradation), but the concentrations increased when SRT changes from 40 days to 106 days (probable accumulation of non biodegradable compounds).

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Flux-step method for the assessment of operational conditions in a submerged membrane bioreactor

Water Science & Technology ◽

10.2166/wst.2016.071 ◽

2016 ◽

Vol 73 (9) ◽

pp. 2222-2230 ◽

Cited By ~ 1

Author(s):

Ezio Ranieri ◽

Vito Goffredo ◽

Mariachiara Campanella ◽

Michael W. Falk

Keyword(s):

Membrane Fouling ◽

Membrane Bioreactor ◽

Pressure Variation ◽

Operating Conditions ◽

Short Term ◽

Step Method ◽

Operational Conditions ◽

Submerged Membrane Bioreactor ◽

Separation Membrane ◽

Solids Separation

A flux-step method was used for monitoring the pressure variation in a solids separation membrane at different operating conditions. A submerged membrane bioreactor pilot plant, used during the short-term tests, was used to purify actual restaurant wastewater. The influence of membrane backwash and relaxation on the variation of pressure variation was also evaluated. In order to reduce the deposition of irreversible fouling, the authors modified the literature-supported filtration to backwash cycling with filtration and relaxation cycling. The trials maintained a constant filtration to relaxation ratio that was in line with optimal filtration to backwashing ratios found in the literature. The relaxation cycling between two constant flux-steps effectively counteracted membrane fouling and the excessive decrease in average pressure, and it results in a lower waste of energy and water than a backwashing strategy.

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Understanding the influence of operating parameters throughin silicooptimization of energy consumption of submerged membrane bioreactor for urban wastewater treatment

Desalination and Water Treatment ◽

10.1080/19443994.2015.1081631 ◽

2015 ◽

Vol 57 (35) ◽

pp. 16363-16375

Author(s):

Yusmel González Hernández ◽

Ulises Javier Jáuregui Haza ◽

Claire Albasi ◽

Marion Alliet

Keyword(s):

Wastewater Treatment ◽

Energy Consumption ◽

Membrane Bioreactor ◽

Operating Parameters ◽

Urban Wastewater ◽

Submerged Membrane Bioreactor ◽

Urban Wastewater Treatment

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Investigation of biological and fouling characteristics of submerged membrane bioreactor process for wastewater treatment by model sensitivity analysis

Water Science & Technology ◽

10.2166/wst.2004.0135 ◽

2004 ◽

Vol 49 (2) ◽

pp. 245-254 ◽

Cited By ~ 15

Author(s):

J.W. Cho ◽

K.-H. Ahn ◽

Y.H. Lee ◽

B.-R. Lim ◽

J.Y. Kim

Keyword(s):

Sensitivity Analysis ◽

Wastewater Treatment ◽

Membrane Fouling ◽

Membrane Bioreactor ◽

Model Simulation ◽

Operating Conditions ◽

Effluent Quality ◽

Submerged Membrane Bioreactor ◽

Fouling Characteristics ◽

Bioreactor Process

In this study, a mathematical model for the submerged membrane bioreactor (SMBR) was developed. The activated sludge model No. 1 (ASM1) was modified to be suitable for describing the characteristics of the SMBR, and the resistance-in-series model was integrated into the ASM1 to describe membrane fouling. Using the newly developed model, the biological and fouling characteristics of the submerged membrane bioreactor process for wastewater treatment was investigated by sensitivity analysis. The sensitivity of effluent COD and nitrogen, TSS in the reactor and membrane flux with respect to each parameter (Kh, μH, KS, KNHH, KNOH, bH, YH, μA, KNHA, bA, YA, Km and α) was investigated by model simulation. As a result, the most important factors affecting membrane fouling were hydrolysis rate constant (Kh) and cross-flow effect coefficient (Km). Heterotrophic yield coefficient (YH) had a great influence on effluent quality. Effluent quality was also somewhat sensitive to Kh. Peculiar operating conditions of the SMBR such as long solids retention time (SRT), absolute retention of solids by membrane and high biomass concentration in bioreactor could explain these model simulation results. The model developed in this study would be very helpful to optimize operating conditions as well as design parameters for a SMBR system.

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