Study On Coagulation Treatment Of Biological Treated Semi-Coking Wastewater

Coagulation treatments of biological treated semi-coking wastewater have been studied in this paper. Coking wastewater treatments were referenced during the study. A Treatment technology of the biological treated semi-coking wastewater was defined. Contaminants of the water, treated by this way, can meet the first demand of the integrated wastewater discharge standard (GB8978-1996).At first, separate treatment of the biological treated semi-coking wastewater by coagulants were studied. Coagulants used in the treatment were PFS, PAC and FeCl₃. Optimum conditions of coagulants strength, pH value and sedimentation time were studied and defined. And the treatment effects with the optimum conditions were compared. The results showed that PFS was the best coagulant in the separate treatments. Remaining contents of COD_cr, NH3-N and chroma were 90mg/L,62.3mg/L and 65 fold after the treatment of PFS. Remaining contents of COD_cr and chroma have met the first demand of the integrated wastewater discharge standard but the remaining content of NH3-N haven't.Then, the coagulant aids were compared and the best coagulant aid was selected. The treatment effects of semi-coke, activated carbon, bentonite, peat, diatomite were compared. The results showed that, the assist effects of activated carbon and semi-coke were the best. The assist effects of peat and diatomite were not significant. The semi-coke is cheaper than activated carbon, so semi-coke was selected as the best coagulant aid in this study.At last, the orthogonal experimental of PFS and semi-coke was studied. Three coagulants strength of PFS and semi-coke were selected as the affecting factors in the study. The treatment effects were compared. The results showed that, with the optimum conditions the assist effect of NH3-N was significant. After the treatment, the removal of COD_cr, NH₃-N and chroma were 87.39%, 88.19% and 79.03%. Remaining contents of COD_cr, NH3-N and chroma have met the first demand of the integrated wastewater discharge standard.