[Effect of carbon source and nitrate concentration on denitrifying dephosphorus removal and variation of ORP]

Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by SBR process was systematicaly studied, at the same time the variation of oxidation reductiun potential (ORP) was investigated. The results showed the phosphate release rate and the denitrifying and dephosphorus uptake rate in anoxic phase increased with the high carbon source concentration under anaerobic condition (100-300mg/L). However when the carbon source added in anaerobic phase was high to 300mg/L, the residual COD inhibited the succeed denitrifying dephosphorus uptake. High nitrate concentration (5, 15, 40mg/L) in anoxic phase increased the initial denitrifying dephosphorus rate. Once the nitrate depletes, phosphate uptake changed to phosphate release. Moreover, the time of the turning point occurred later with the higher nitrate addition. ORP can be used as a control parameter of phosphorus release, and it can also indicate the denitrificaiton react degree during the anoxic phosphorus removal but can't be used as control parameter of phosphorus uptake.