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Practical materialization physical chemistry-biodegradation- 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. Optimum technological parameters were explored. The results showed that the effluent water quality was improved after the treatment, such as CODCr≤120mg/l,NH3-N≤25mg/l.The Other indexes met the second grade of the national discharge standards.Coagulating sedimentation method was applied in Pre- physicochemical treatment. Pilot test determined that the water volume is 3500 m3/h. PAC optimal dosage 500ppm, the best HRT was 1.35h. 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 2.0-4.0 mg/L, pH 7.5-8.0, internal recycle ratio of 120%, sludge return ratio of 120%, SRT of 20d, HRT of 21.6h.Coagulating sedimentation method was applied in the post- physicochemical treatment again combining with High Dense SettlingPond. Experimental results showed that the effective coagulant was PFS.Pilot test confirmed that PFS effective dosage was 800-1000 ppm, the best HRT was 0.79h, single pool of water load for High Dense Settling Pond was 1500 m3/h.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.
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