Study On Enhanced Treatment Of Municipal Wastewater And The Effluent From Anoxic And Velocity-Variable Bio-Filter(ABF) By Coagulation

Anoxic and velocity-variable bio-filter was taken more consideration in municipal wastewater treatment with the advantage of low energy consumption, convenient management and so on, but because the COD,BOD etc in its effluent can't meet the requirement of national wastewater discharge standard, its usage was limited. At the same time, coagulation has such advantages as short treat-time, small occupied-land, stable disposal effect, remarkable removal of phosphorus and so on. Therefore, the research discussed the feasibility of using coagulation to improve the effluent from ABF, and contrasted with chemically enhanced primary treatment (CEPT). The results show using coagulation to improve the effluent from ABF is feasible, and main water quality in supernatant except nitrogen can meet the requirement of national wastewater discharge standard (GB8978-96). By comparison, poly-ferric sulfate(PFS) is determined as a better kind of coagulant than poly- aluminum chloride(PAC) and poly-ferric sulfate-silicate. When the COD, P and SS value in the supernatant reach the forgoing stadard, the optimal conditions are that velocity gradient G is 60 s-1, flocculation time is 10 minutes, the dosage of poly-ferric sulfate (PFS) is 49.5mgFe/L. In addition, the experiential formula of removal efficiency of COD is deduced by regress orthogonal-experiment when the influent fluctuates in certain range. The formula of sludge production is also determined.The results also show that CEPT for medium concentration municipal wastewater(when the COD value is ranged from 250mg/L to 400mg/L ) can't meet the first class requirement of national wastewater discharge standard, When the COD value in effluent of CEPT reach the inferior requirement ,the optimal conditions are that G is 80 s-1,t is 10min, the dosage of PFS is range from 66mgFe/L to 99mgFe/L,and the dosage of PAM is 0.6mg/L, in the circumstances, the P and SS value in supernatant can meet the first class standard. Similarly, the experiential formula of removal efficiency of COD, P, NH3-N and SS are deduced when the influent fluctuates. The formula of sludge production is also determined.By contrast, conclusion can be drawn that coagulation enhanced the effluent of ABF is far lower than CEPT in whichever the dosage expense or sludge production.