Study On Speciation And Removal Of Phosphorus In Tail Water From Municipal Wastewater Treatment Plant

Phosphor is the limiting factor which can control or lead to eutrophication,a large-scale outbreak of algae in Taihu lake was broken once again in 2007.After it caused water supply crisis in Wuxi city,the state made more stringent emission requirements to the Taihu lake basin urban wastewater treatment firm of tail water,many urban wastewater treatment finns are facing upgradeing of the removal of nitrogen and phosphorous technology.This paper is the experimental study of the chemical coagulation phosphorus removal to the Taihu lake basin urban wastewater treatment firm of tail water which treated by A/O process.Through the analysis to the content of each phosphorus forms in tail water,the total regularity of each phosphorus forms content as follows: solubility total phosphate content＞solubility orthophosphate content＞particulate phosphorus content＞other dissolved phosphorus content,of which solubility orthophosphate content is accounted for 76.82%(mean) of total phosphorus content.According to the results of analysis for the phosphorus forms,it provides the basis for the appropriate phosphorus removal method of the follow process.Through the coagulation tests,compared the phosphorus removal effect of used coagulant,studied the impact factors of phosphorus removal by coagulation.The results show that the PFS,PAC and FeCl₃ are better coagulant for phosphorus removal,of which the effect of PFS is the best.For the water samples of total phosphorus(TP) at 1.46mg/L,when add PFS,PAC and the ferric chloride dosage at 15 mg/L,20 mg/L and 25 mg/L,will enable the TP＜0.5 mg/L of the effluent by coagulation-sedimentation. FeCl₃ had great influence by pH,while the PFS could suitable for wide scope of pH.The best pH of three coagulants as follows: 8,7and 6.Through the comparative test of the phosphorus removal effect by adding different types of PAM,we found that the anionic PAM had no aid-coagulation effect on three coagulants,and the non-ionic PAM had some aid-coagulation effect on PAC and FeCl₃ but on PFS was not obvious.Through the study of the dosing method of the non-ionic PAM, we found that the phosphorus removal effect of adding coagulant at first, then adding non-ionic PAM after slow agitation about 3min was better than adding coagulant and non-ionic PAM at the same time.Three coagulants had some effect on COD_Cr removal of effluent water,improving the dosage of ferric salts coagulant could increase the chroma of effluent water obviously,improving the dosage of three coagulants could increase SS of effluent waterAccording to the phosphorous removal effect of each coagulant,the combined effect of the flocculant and the other water quality indicators removal efficiency of the effluent,PAC is the most suitable coagulant for phosphorus removal.