A Pilot-scale Study Of Hybrid Membrane Bioreactor Applied To Campus Wastewater Treatment

Hybrid Membrane Bioreactor （HMBR） was applied to treat campus wastewater.Compared to Conventional Membrane Bioreactor （MBR）, HMBR added carrier intoMBR, which makes suspended biomass and attached biomass existed in the reactorsimultaneously. Both kinds of biomass play the role of organic pollutantbiodegraduation and promoting nitrogen and phosphor removal effiency. A pilot-scaleHMBR was carried out in Xi’an Siyuan Wastewater Treatmen Plant. The performanceof HMBR was focused on pollutant removal efficiency, the extraction methods andanalysis of Extracellular Polymeric Substances （EPS）, activated sludge characteristicand membrane fouling control.More than five months continuous monitoring, the result showed that HMBR couldkeep stable operation and resist the loading fluctuation. Under low load operation,HMBR also had high removal efficiency for COD, TOC, UV₂₅₄, NH3-N, the averageremoval rate was90.63%,98.8%,40.41%,98.43%, respectively. Nitrogen and phosphorremoval effiency of HMBR was strongly inffluented by organic loading, the removalrate reached to33.18%and30.49%. The average removal rate of Chroma was97.18%.The removal rate of turbidity was nearly100%, turbidity almost could not be detected ineffluent water. Through the biological treatment and membrane filtration, the number oftotal bacteria and E. coli could meet "Miscellaneous Urban Water Quality Standard"（GB/T18920-2002）. After disinfection, the effluent water could be reused safely.Four methods including high-speed centrifugation, ultrasonication, cationexchange resin, heating were employed for extracting EPS of activated sludge fromHMBR. Chemical analysis method combined with excitation–emission matrix （EEM） and gel-permeating chromatography （GPC） to estimate these four methods. Theexperimental results revealed that heating method employing60℃for30minutesshowed the best extracting effect and caused little damage to the cell. The boundedExtracellular Polymeric Substances （BEPS） in cake layer of membrane face was morethan in activated sludge mixed liquor. Comparing the ratio of polysaccharides toproteins in activated sludge mixed liquor and cake layer, the result showed that the ratioof polysaccharides to proteins in cake layer was larger.There exsited two kinds of biomass in HMBR at the same time, therefore, it couldincrease biomass, and also improve the characterization of sludges. The average particlediameter of activated sludge flocs in HMBR was nearly to56.85μm, which was morethan one times as large as flocs in CMBR in literature. The mechanism of membranefouling formation was discussed. Transmembrane pressure （TMP） of the membranemodule was monitored continuously during the whole operation. Meanwhile, membranefouling behavior was observed. Through adjusting reactor structure, optimizingoperation conditions and applying physical-chemical cleaning, it could controlmembrane fouling effectively. After106days of continuous operation, TMP was up to20kPa which was preset value of chemical cleaning. During one period of106days, thedTMP/dt was about0.2kPa/d.