Effects of Nitrate on Denitrifying Phosphorus Removing and the Process Control

Based on the characteristics of low carbon source of municipal wastewater in the southern regions, this paper studied the effects of different concentration and addition mode of nitrate on denitrifying phosphorus removal with nitrate as electron acceptor,and it was specially studied that the control strategy with on-line monitoring V(ORP)and pH.The experiments showed that the higher or lower concentration of nitrate in anoxic phase can lower simultaneous phosphorus and nitrogen removal.In order to achieve good and stable simultaneous phosphorus and nitrogen removal over time,the concentration of nitrate should be in a proper range.With on-line monitoring V(ORP)and pH,there would be a turning point in pH when nitrate was used up and phosphorus uptake ended,if nitrate wasn't enough.When phosphorus uptake ended with nitrate enough,there was a plat in pH.So pH can reflect the condition of phosphorus uptake and denitrifying in anoxic phase and can be used to optimize and control denitrifying phosphorus removal processes.While there wasn't any characteristic point in V(ORP)to infer the condition of phosphorus uptake and denitrifying in anoxic phase,V(ORP)can't be the controlling parameter in denitrifying phosphorus removal processes.The addition mode of nitrate couldn't affect the efficiency of simultaneous phosphorus and nitrogen removal,but it was favorable to advance denitrification rate and decrease accumulation of nitrite along with addition number of frequency increasing and continuous addition with low concentration nitrate especially.