| Submerged membrane bioreactor (MBR) for the treatment of contaminated water is composed by highly efficient membrane separation technology and conventional activated sludge biological treatment plant. Due to the effect of interception of the membrane, it can separate solid from liquid without the final clarifier, and all the biomass can stay in the reactor to achieve higher biomass concentration. Thus this technology has the advantages of small footprint, high quality effluent, complete so lid-liquid separation. Denitrification is also obtained simultaneously in the A/O-MBR system, leading to a hotspot in the field of wastewater treatment and water reuse.A multi-habitat A/O-MBR system was built in this study, striving to achieve coexistence of multi-habitat in a membrane bioreactor, which will render the diversity of microbial community richer. Mix liquor was pump from the anoxic zone to the oxic zone without any recycle pump but by liquor pressure formed by agitation and aeration. An auto control system of programmable logic controller (PLC) was used to accurately monitoring the agitation speed of A/O-MBR automatically. The reactor was continuously operating for 120 days without any sludge discharged to study the biomass proliferation and it impacts on loosely extracellular polymeric substance (EPS1) content and sludge apparent viscosity and their further impacts on membrane fouling and DO transfer efficiency. Results showed that the biomass increasing led to a gradual increase of EPS1, as well as sludge apparent viscosity. Positive correlation relationships were present among MLSS, EPS1, and sludge apparent viscosity. With increasing biomass, the protein increased significantly, while polysaccharide was relatively constant, indicating increasing of protein was the main cause to increasing viscosity. Besides, with increasing of the MLSS, EPS1 and sludge apparent viscosity, TMP increased and DO transfer efficiency decreased, indicating that increase of MLSS,EPS1 and sludge apparent viscosity accumulate membrane fouling and hinder DO transfer.The degradation efficiencies of different concentrations of organic pollutants and nitrogen pollutants as well as impact resistant ability of the system were investigated. Results showed that the system had highly efficiency and stability for removal of organic pollutant (COD, TOC) and obtained efficiently removal of nitrogen pollutants (NH3-N, TN) when specific conditions were achieved. Average removal rate of COD, TOC, NH3-N, TN were 94.6%,97.9%,97.3%,60.5%, respectively. Membrane interception played a vital role in TOC removal, and its average removal rate was 81.2%. Effectiveness removal of nitrogen pollutants relied on biomass and DO level, higher than 2 mg/L of DO in O zone and lower than 0.5 mg/L of DO in A zone were crucial. Improving the influent organic compounds and ammonia concentration did not affect the degradation efficiency of the system, showing that the multi-habitat A/O-MBR system have a stronger ability to resist shock.Abundance of substrate leading to rapid proliferation of biomass was benefit to improve specific sludge activity. Dehydrogenase activity (DHA) and adenosine triphosphate (ATP) were used as indicators of specific sludge activity, which increased when biomass proliferation were under rapid conditions while decreased when stable proliferation period and decay period. With prolong of SRT, both inorganic substance and biomass increased unceasingly, however, biomass proliferation was limited by substrate and inorganic substance accumulation, thus SRT extension led to sludge aging, increased proportion of inorganic substance and lowered the sludge activity. Results showed that both DHA and ATP were appropriate to evaluate sludge activity in an A/O-MBR system. |
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