Study on Denitrifying Phosphorus Removal From Domestic Wastewater in A²O Process

A lab-scale A²O process was operated to investigate the performance of biological nutrients removal and denitrifying phosphorus removal from low ρ(C)/ρ(N) ratio domestic wastewater.The results showed that only about 47.1% of TN could be removed with effluent ρ(NO₃^--N) above 35mg/L when the A²O process was operated without the pre-anoxic zone and additional carbon source.Under this condition,both conventional and denitrifying phosphate removal was not observed in the anoxic zone.When the A²O process was operated with the pre-anoxic zone,about 60.7% of TN and 55.9% of PO₄^3--P could be removed.Moreover,denitrifying phosphate removal occurred with a removal efficiency of 31.4%-46.9% in the anoxic zone.After the ρ(C)/ρ(N) ratios were increased by adding the carbon sources,biological nutrients removal was enhanced with the TN removal of 74.4% and the ρ(PO₄^3--P) in the effluent below 0.5mg/L,and the denitrifying phosphate removal efficiency was up to 66.2%-90.9%.Furthermore,the variations of PHA and glycogen were investigated.The relative metabolic activity of the DNPAO(denitrifying phosphate accumulating organism) increased from 31.1% in the seed sludge to 74.7% in the acclimated sludge.The carbon sources utilization efficiency is upgraded with the achievement in denitrifying phosphate removal in the A²O process.