In-situ sludge reduction and simultaneous phosphorus removal in A²O and side-stream induced crystallization coupling system for treating domestic wastewater.

Biofilm in-situ sludge reduction process can reduce the yield of excess sludge and restrict biological phosphorus removal efficiency. In this study, a novel in-situ sludge reduction coupled side-stream induced crystallizing (SIC) phosphorus removal process was proposed. The feasibility of simultaneous high efficiency in-situ sludge reduction and removal of nutrients from domestic sewage, and SIC phosphorus removal potential were investigated. The results showed that operation effect of A²O-SIC was excellent with anaerobic supernatant side-stream flow ratio 40%, and pH 8, reaction time 30 min, seed size 100-150 mesh, aeration volume 300 L/h, Ca/P ratio 2.5, and seed dosage of 50% in SIC. The γ_obs of A²O-SIC was 0.18±0.05 g MLSS/g COD reducing 18.18% excess sludge than A²O sludge reduction process. The average concentration of effluent TP was 0.54 mg·L-1, and the removal rate was 88.89%. SIC does not affect the microbial activity of the biological system, whereas Ca²⁺ in the reflux liquid can promote the production of extracellular polymer and consequently, the formation of biofilm. Energy dispersive spectrometer test found that the proportion of P element on the seed crystal surface was significantly increased. In addition, the anaerobic area dominant species were Thauera, Methyloversatilis in the A²O-SIC and biological phosphorus removal was not inhibited. The experimental results provide an effective solution for simultaneous high-efficiency in-situ sludge reduction and phosphorus removal in wastewater treatment. [ABSTRACT FROM AUTHOR]