Materialized - Biochemistry - Materialized Combined Process Of Chemical Wastewater

Practical materialization physical chemistry-bio-chemistry-physical chemistry combined process routes was put forward in this paper according to the basic characteristics and practical situation of the wastewater in a large sewage treatment plant in ZheJing province. Small experiment and pilot test were studied to explore the optimum technological parameters. The effluent water quality met the second grade of the national discharge standards after the treatment.Coagulating sedimentation method was applied in Pre-physicochemical treatment. PAC has been chosen because it's most cost-effective, the best condition was:pH8, reagent dosage of 400ppm, 120-180r/s stirring speed,0.5 min, standing time of 30 min. Under that condition,20% COD was removed. Pilot test futher determined that the water volume is 3500 m3/h. PAC optimal dosage 400ppm, the best HRT was 1.16h. The limit of field devices on PAC and water load were 600 ppm,3500 m3/h respectively.Activated sludge was used in the biochemical Treatment. The optimum technological parameters for bichemical system of the plant were that:DO concentration of 1.5-3.5 mg/L, pH 7.5-8.0, internal recycle ratio of 100%, sludge return ratio of 100%, SRT of 20d, HRT of 26h.Coagulating sedimentation method was applied in the post-physicochemical treatment again combining with High Dense Settling Pond. Experimental results showed that the effective coagulant was PFS, when the dosage of 800 ppm in the pH range of 6-9, COD removed rate reached 31.3% and color removal rate was 75%, all indexes can meet the emission standard; COD was only 168 mg/L and color was 64 times when the optimal PFS dosage was 1000ppm in the pH range of 6-9. Pilot test futher confirmed that PFS effective dosage was 800-1000 ppm, the best HRT was 0.71h, single pool of water load for High Dense Settling Pond was 1500m3/h.According to bio-chemical effluent with high chlorine and low COD in the Plant, COD determination method is also studied for finding the most simply and effective way to eliminate the interference of chlorine ion in this article. The results showed that any of the following methods can reduce the interference of chloride ions:15:1 mass ratio of HgSO4/ Cl-,0.20 mol/L of K2Cr207, diluting the water sample to 0.75 times.28 mL of Ag2SO4-H2SO4.The research results showed that physical chemistry bio-chemistry-physical chemistry combined technology is advanced and reliable, targeted, low running costs, simple operation and management, running effective. It not only has important practical significance on the wastewater treatment of the plant, but also takes the demonstration effect on the whole wastewater treatment industry, in a word, it has broad application prospects.