Effect of in-stream electron acceptor on phosphorous release behaviour of excess activated sludge
内源电子受体对剩余污泥释磷行为的影响

In this study,a novel in-stream electron acceptor,which generated from the reject water treatment process using excess activated sludge of the biological nitrogen(N) and phosphorous(P) removal process as nitrobacter,was used to control P-release from the P-enriched excess activated sludge(EAS) during gravity thickening process.The objectives of this study were(1) to determine the optimal nitrification time for in-stream electron acceptor(i.e.nitrate) generation from the reject water treatment system using EAS as nitrifying bacteria and(2) to investigate the P-release characteristics of EAS during the gravity thickening process using in-stream electron acceptor as inhibitor.Experimental results showed that the optimal nitrification time for in-stream electron acceptor(i.e.nitrate) generation is 24 h which can lead to the ammoniumcal-N in the reject water decreased from 41.20 mg/L to 0.19 mg/L while the nitrate increased from 1.14 mg/L to 32.62 mg/L.This indicates that the nitrate,an in-stream electron,was generated and can potentially be used as inhibitor to reduce the amount P-release from EAS during the gravity thickening process.The results showed that the phosphorus in the reject water was changed to 44.87 mg/L when the in-stream electron was 36.16 mg/L.This results in 65.44% of P-feedback through reject water recycling decreased.Meanwhile,the in-stream nitrate decreased from 36.16 mg/L to 4.84 mg/L.The amount of ammoniumcal-N feedback through reject water recycling decreased from 100% to 17.68%.This indicates that significant amount of P and N feedback in the biological N and P removal process can be reduced using the in-stream electron acceptor.