[Real-time process control of denitrifying phosphorus and nitrogen removal systems with NO3(-) and NO2(-) as electron...

The simultaneous phosphorus and nitrogen removal using denitrifying phosphate-accumulating organisms with NO3(-) and NO2(-) as electron acceptors was investigated in an anaerobic/anoxic process. The results showed that the concentrations of COD, PO4(3-) and electron acceptors (NO3(-) and NO2(-)) have a correlation with the variation of pH and ORP during anaerobic/anoxic process. In anaerobic phase, the occurrence of pH flat indicates the end of phosphorus release. In anoxic process, an inflexion was observed in ORP profile when the phosphorus uptake was finished. In addition, the phosphorus uptake rate was investigated in the process with different electron acceptors (NO3(-) and NO2(-)). The average anoxic phosphate uptake rate was 32.68 mg/(L x h) in the early 30 min during anoxic phase when NO3(-) was as electron acceptor, and every 1 mg PO4(3-)-P uptake would consume 1.14 mg NO3(-)-N. In the process with NO2(-) as electron acceptor, the average anoxic phosphate uptake rate was 17.66 mg/(Lx h) in the early 30 min, and every 1 mg PO4(3-)-P uptake would consume 1.57 mg NO2(-)-N. In conclusion, ORP and pH can be used as control parameters for simultaneous phosphorus and nitrogen removal in an anaerobic/anoxic process, and the system with NO3(-) as electron acceptor is superior to the system with NO2(-) as electron acceptor.