Effect of Chemical Phosphorus Precipitation on Enhanced BiologicalPhosphorus Removal in MBR Application to Achieve ExtremelyLow Effluent Total Phosphorus

摘要

Pilot test indicates that the University of Cape Town (UCT) process combined with membranernbiomass separation and chemical precipitation is able to achieve a very low total phosphorous (TP)rnconcentration of <0.032 mgP/L under constant flow conditions. With chemical dosed into in a chemicalrncontact tank between the aerobic bioreactor and membrane tank and chemical precipitation take place inrnthe contact tank down steam of aerobic bioreactor, the average soluble TP concentration in aerobicrnbioreactor was averaged at 0.23 mg/L, which is about one order of magnitude higher than MBR effluent.rnThe nitrification, de-nitrification and BOD/COD removal was not affected by low soluble phosphorusrnconcentration as necessary nutrient. Some data hints the biological phosphorus removal was not veryrnactive, that is probably because the ortho-phosphate concentration in aerobic bioreactor is low andrnphosphors accumulation organisms can not accumulate enough poly-phosphate.rnFive process operation scenarios were simulated using BioWin (2006). Steady state simulationrnshows biological and chemical phosphorus removal can take place together and chemicalrnphosphorus precipitation does not obviously changes the population of phosphorousrnaccumulation organisms. However, dynamic simulation shows the competition between thernchemical phosphorus removal and biological phosphorus removal at the dynamic situation mayrnmake the operation difficult. This bring a topic that needs further investigation: How to developrnan reliable online phosphorus analyzer and use model to feed forward control alum dosing thatrnmay keep both chemical and biological phosphorus removal efficient.