Phosphorus source in aerobic systems
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Recently, biochemical tuning was carried out using the AAO + contact oxidation process. During operation, the addition of phosphorus was gradually reduced, and it was observed that the phosphorus level in the last contact oxidation tank showed an upward trend (1.2 mg/l), while the phosphorus level in the aerobic tank was only 0.03 mg/l. By returning sludge to the anaerobic system at the front end, the phosphorus levels in the anaerobic and anoxic tanks were increased over time; however, the phosphorus level in the aerobic tank did not increase as much as expected. It is necessary to determine whether a certain amount of phosphorus should be added to the aerobic tank. The COD in the aerobic tank is 750 mg/l, and the ammonia nitrogen level is 16 mg/l. Is it necessary to add phosphorus in proportion? If so, to what level should the phosphorus content be increased?
The phosphorus level in the aerobic tank is only 0.03 mg/l, which is too low; it cannot provide the nutrients necessary for the growth and reproduction of activated sludge, so supplementation is required. Generally, if the TP level in the effluent from an aerobic secondary sedimentation tank is not less than 0.5 mg/L, there is no need to supplement phosphorus.