| In order to meet increasingly stringent discharging requirements of phosphorus inmunicipal wastewater treatment and achieve phosphorus removal and recovery from thewastewater efficiently, side-stream P removal process that combined with biologicaland chemical methods should play an important role in phosphorus removal andrecovery from the wastewater treatment, but there are still lack of enough studies andexperience on applications of side-stream P removal process by now，so it is necessaryto study the effects of phosphorus stripping on removal of pollutants and activity of themicrobial ecosystem.Based on comparison of BCFS, PhoStrip and ERP-SBR, it is speculated thatanaerobic tank is a potential advantage position of phosphate recovery. If part of themixture with phosphorus fully released by PAOs, is drawn out from the anaerobic tankinto a secondary sedimentation tank in side stream, then phosphorus in the supernatantwith high concentration is stripped by chemical precipitation. Effluent from chemicalsedimentation tank after chemical P removal and the sludge from the secondarysedimentation tank are sent back to the aerobic section of main stream to let PAOs takein phosphorus further. This will be a new process named as anaerobic supernatantphosphorus stripping process (ASPS process). In this thesis, both synthesizedwastewater with sodium acetate as the sole carbon source and synthesized domesticwastewater were used to investigate the effects of chemical phosphorus stripping inASPS process on biological P removal in the main stream of an AO system operated inthe ratio of33%of chemical P stripping in side-stream. The study is considered to behelpful for establish the foundation of the new phosphorus removal treatment process.The main results drawn from the study are as follows. (1) The efficiency of phosphorus removal is93.81±3.67%with sodium acetate asthe sole carbon source before chemical phosphorus stripping and96.14±2.17%after. Inthe case of synthesized domestic wastewater, they are86.44±2.99%, and88.54±2.68%,respectively. The efficiencies of COD removal are80.68±1.56%and83.06±2.24%, aswell as83.10±1.46%and82.86±2.45%correspondingly. It is shown that theefficiencies of phosphorus and COD removal in the system are not affected by chemicalphosphorus stripping.(2) Chemical P stripping in sidestream has great effects on settle ability andparticle size of the sludge.A lot of filamentous bacteria proliferated and entangled withthe activated sludge flocs. The settle ability of the sludge was deteriorated, and theparticle size became smaller.(3) After chemical P stripping in sidestream, the concentration of P in anaerobictank decreased, which the advantages of phosphorus recovery from sidestream lostgradually. Even though the recovery ratio of phosphorus from sidestream decreased tothe level as that directly precipitated from influent, but phosphorus removal andrecovery achieved effectively to some extent.(4) In the case of treating synthesized domestic wastewater, chemical P stripping insidestream had few effects on PAOs’ phosphorus absorbing and releasing ability. Theintracellular PHA and glycogen levels did not change significantly from the view of theenergy and material metabolism of the microorganisms in the early stage. However,intracellular Poly-phosphate content decreased with chemical P stripping, resulting ininhibition of phosphorus release. It is better to reduce side-stream ratio or stop chemicalstripping for a period of time to make PAOs accumulate enough Poly-phosphate beforeproceeding the next chemical P stripping. |
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