Proliferation Of Biomass And Its Impact On The Performance And The Torque Rheological Properties Of A Submerged Membrane Bioreactor

Submerged membrane bioreactor (sMBR) was a water treatment combined by a highly effective membrane separation technology and activated sludge biological treatment unit. Due to the effect of interception of the film, it could separate solid from liquid without the second pond, and all the biomass could stay in the reactor and achieve higher biomass concentration. Thus this technology had the advantages of small footprint, high quality effluent, completed solid-liquid separation and so on. In the process of the operation, membrane module was susceptible to pollution, causing the loss of membrane flux, resulting in performance reduction of the membrane and the increase of operating costs, hindering its wide application. Research showed that the concentration of biomass in the reactor was one of the important influence parameters of sMBR operation, it not only affected the removal effect of pollutants, also affected the sludge characteristics of viscosity, content of extracellular polymers (EPS) and so on in sMBR. Therefore, high biomass concentration was a necessary guarantee of efficiently purifying sewage, but also the key factors of increasing membrane pollution and hindering the rapid mass transfer (such as oxygen, nutrient transfer, transfer of metabolites), which affected operation efficiency of the overall system.Based on the effects of the contradictory caused by biomass concentration in the operation process of sMBR, this experiment adopted the auto control system of programmable logic controller (PLC) monitoring the operation of sMBR automatically. Under the condition of no sludge discharge, to study the biomass proliferation rule and the effect of the operation efficiency under biomass proliferation process in sMBR. So as to optimize operating conditions of the process and providing basic basis for reasonable design of the reactor.A programmable logic controller (PLC) was used to control the process of the sMBR. After operating for20-40days with no discharge of sludge, the concentration of biomass attained9670mg/L, every indexes in the effluent achieved the optimal effect. However, as the proliferation of biomass, the apparent viscosity of sludge increased markedly, which led to decreasing of the F/M and difficulty in mass transfer, and inhibited the activity of sludge as well as deteriorated the quality of effluent. Results also indicated that the increasing trend between the apparent viscosity and MLSS, EPS were rather similar, which revealed that these two factors had a very obvious influence on the apparent viscosity of sludge. Additionally, a SEM/EDS method was used to observe the morphology of the membrane surface and analyze the elemental composition, the results indicated organic pollutants were the main components in the fouling layer of the membrane modules, and the inorganic components accounted for a less ratio.Under the condition of no discharge, the system continuously operated87days, the experiment research showed that apparent viscosity and concentration of biomass, sludge rheological torque of the mixture had a positive correlation. When the concentration of the sludge and the apparent viscosity higher were, with which the Pearson correlation coefficient of the sludge rheological torque was higher. Under the condition of continuous effluent, the TMP, TMR, and the rising speed of membrane filtration were much bigger and faster than the intermittent effluent.