Effect Of Sludge Retention Time And Initial PH On Phosphorus Removal In Aerobic/Extended-idle Regime

Eutrophication seriously endanger water purification capacity, and resulting in great harmto the aquatic environment. Thus resulting in contamination of water resources. Effectivecontrol of phosphorus into water bodies can effectively control the eutrophication of waterbodies occur.In this study, Sodium propionate was adopted as the sole carbon source in sequencingbatch reactors (SBR) to study the effect of Sludge Retention Time and initial pH on biologicalphosphorus removal in aerobic/extended-idle regime.To study the effect of sludge retention time, four sequencing batch reactors (SBR) withfour sludge retention times (SRT. R1:9d; R2:12d; R3:18d; R4:24d) were introduced tostudy the effect of SRT on biological phosphorus removal in aerobic/extended-idle regime.the phosphorus removal efficiencies were65%,91.5%,96%, the phosphorus removal rate peruint VSS were3.07,4.62,4.70,3.59mg-P/g-VSS, and the SVI were averagely89,93,98,123mL/g respectively. Experimental results showed that with increasing SRT, the phosphorusremoval efficiency and removal rate per uint VSS first rose and then descended, and reached amaximum at a critical SRT of18d, while the settling performance of sludge stepped down.According to the changes of intracellular polymers in SBRs, microorganism synthesisedpoly-β-hydroxyalkanoates (PHA) using glycogen at the stage of exogenous substratesconsumption in R1, while there didn’t exist substantial absorption of phosphate at the stage ofPHA consumption, which indicated a metabolic way of GAOs; in R2, R3and R4,microorganism synthesised PHA using TCA at the stage of exogenous substrates consumption,and synthesised large amount of Poly-P at the stage of PHA consumption, which implied ametabolic way of PAOs.To study the effect of initial pH, three sequencing batch reactors (SBR) with three initialpHs(R1:6.4; R2:7.2; R3:8.0) were introduced to study the effect of initial pH on biologicalphosphorus removal in aerobic/extended-idle regime. the phosphorus removal efficiencieswere34.2%,85.0%,93.3%and76.7%, the phosphorus removal rate per uint VSS were1.97,4.21,4.40mg-P/g-VSS respectively. The phosphorus removal efficiency and removal rate peruint VSS increased as the intial pH rose. When the initial environment is acidic，thephosphorus removal efficiency is not so good, but when the initial environment is neutral oralkaline, the phosphorus removal efficiency is so good. According to the changes ofintracellular polymers in SBRs, In SBR1where the intial environment is acidic, themicroorganism in the system express a metabolic way as GAOs; As in SBR2and SBR3where the intial environment is neutral and alkaline, the microorganism in the system express ametabolic way as PAOs.