[Simultaneous nitrogen and phosphorous removal under low DO in a hybrid biological reactor]

Study was conducted by use of the mixed organism of activated sludge and suspended biofilm coexisting in a hybrid biological reactor (HBR) system for simultaneous nitrogen and phosphorous removal. The experimental results showed that, DO and COD/TN were the main factors affected the effluent. The maximum phosphorous releasing rate (the rate of PO4(3-)-P concentration at releasing end to the initial PO4(3-)-P concentration) was 249%, TN removal efficiency was 80.0%, and PO4(3-)-P removal efficiency was 92.2% by controlling the aeration rate (Qair) at 0.07 m3/h. TN and PO4(3-)-P removal efficiency will be decreased, whenever aeration rate increasing or decreasing. With the increasing of COD/TN, the TN and PO4(3-)-P removal efficiency was increased. TN removal efficiency was increased from 70.3% to 84.9%, and PO4(3- -P removal efficiency was increased from 82.2% to 96.0%, when COD/TN was increased from 3.2 to 10.5. The SVI of the activated sludge was less than 90 mL/g during the experiments. It was found during the research process that high phosphorus and nitrogen removal efficiency can be simultaneous achieved without anaerobic and anoxic phase, which was conventionally considered as a key phase for phosphorus and nitrogen removal.