[Research on substrate transformation mechanism in A2/O process].

Based on a laboratory-scale anaerobic-anoxic-oxic process acclimated with real wastewater, substrate transformation mechanism and the effect of nitrate on substrate transformations occurred in the system were investigated. The results indicated that under the anaerobic condition without nitrate, phosphorus-accumulating organisms (PAOs) could take up 51% of COD consumed and store them to PHAs; anoxic and aerobic specific phosphorus uptake rates were 3.87 mg/(g x h) and 6.54 mg/(g x h), and the anoxic and aerobic ratios of phosphorus uptake and PHAs utilized, nu(P/PHA). were 0.38 and 0.78, respectively. While under the anaerobic condition containing nitrate, only 30.8% of COD consumed was taken up by PAOs and 61.5% was used as the denitrifying carbon source; specific phosphorus uptake rates of anoxic and aerobic sludge were 2.24 mg/(g x h) and 4.58 mg/(g x h), and the nu(P/PHA) under the anoxic and aerobic conditions were 0.35 and 0.77, respectively. Furthermore, in both systems, there was a good linear relationship between COD consumption and phosphate release under the anaerobic condition. The nitrate existed in the anaerobic condition could decrease anaerobic phosphorus release rate and efficiency of PAOs, resulting in a decreased amount of PHAs synthesis and consequently affecting anoxic and aerobic phosphorus uptake rates. However, phosphorus uptake capacity was not influenced by nitrate and the amount of PHAs synthesized in the anaerobic stage.