Anoxic biological phosphorus removal and effect of excessive aeration on biological phosphorus removal in A~2 O process

A pilot-scale nutrient removal activated sludge syste m, based on the A2O configuration, was used to treat brewery wastewater.In the e xperiment, the existence of denitrifying phosphorus removing bacteria (DPB) and the contribution of DPB to phosphorus removal was observed.The tests showed the average total amount of anoxic P uptake accounted for 70% of the total amount of P uptake of the system at steady state, oxygen requirement could be decreased s ignificantly(about 25%).Denitrifying phosphate removal resolved the competition for organic substrates between Poly-P organisms and denitrifiers under lower or ganic loading.Effluent total-P concentration could achieve less than 0.30 mg· L -1 and average effluent total-N was less than 10 mg·L -1 .It is cle arly demonstrated that the phosphorus uptake almost stopped in an over-aerated system, the released phosphorus could not be taken up fully again.Consequently, incomplete phosphorus uptake led to temporary reduction of biological phosphorou s removal efficiency.It took about the time of one sludge age to eliminate that disturbance.