| The effluent from chemical companies in the park usually should be pretreated and reaching influent requirement before discharging into the park sewage treatment plant for centralized treatment. Because of the emissions from chemical industrial park is featured by high toxicity and,complex composition, high salinity, poor biodegradability and great fluctuation in quality and quantity, water quality indicators such as Chemical Oxygen Demand(CODCr), NH3-N are generally not able to meet the first class criteria of Discharge Standard of Pollutants for Municipal Wastewater(GB18918-2002) by conventional biological treatment. With the energy conservation and emission reduction policy is more and more strict, many chemical industrial park sewage treatment plants should be improved to adapt to the modern requirements. So, researching and developing an effective and economic wastewater advanced treatment technology is the key to implement the centralized treatment of chemical industrial combined wastewater.In this paper, biochemical effluent from a chemical industrial park wastewater treatment plant in Zhejiang province was chosen as the research object, iron-carbon micro-electrolysis coupled with calcium hypochlorite oxidation process were utilized for the wastewater of the CODCr and NH3-N treatment in neutral pH conditions. The resourceful disposal of iron mud from iron-carbon micro-electrolysis were also studied at the same time. The main conclusions can be drawn as follows :(1) Without pH adjustment, through the single factor experiments and response surface analyses of iron-carbon micro-electrolysis process the optimum conditions were determined as follows: the scrap iron dosage of 69.1 g/L, the Fe-C mass ratio of 1:3.4, and the reaction time of3.7 h. The optimum flocculation condition: no pH adjustment, the PAM dosage was 1mg/L, and the flocculation sedimentation time was 30 min, and the removal rates of CODCr could reach 57%,the concentration of CODCr in effluent was 67 mg/L. The iron-carbon micro-electrolysis has obvious removal effect for Tributyamine and 2,2’-Methylenebis(6-tert-butyl-4-methylphenol).(2) The optimum conditions of calcium hypochlorite oxidation reactions were as follows: theoptimum calcium hypochlorite dosage was 400 mg/L, no p H adjustment, and the reaction time was 40 min. Under the optimum operation conditions, the removal rates of CODCr and NH3-N could reach 67.2% and 99.9%, and the concentration of CODCr and NH3-N in effluent were less than 52 mg/L and 0.04 mg/L, respectively, meet the first class criteria of Discharge Standard of Pollutants for Municipal Wastewater(GB18918-2002). The combined process is technically feasible and economically reasonable with processing costs only 2.53 yuan per ton of wastewater.(3) According to the researches on iron mud of iron-carbon micro-electrolysis process, we have the conclusion as follows: water content of iron sludge is 69.9% after centrifugation, p H value is 5.5, the content of iron in the mud is 33.1% of the dry basis, Ca, Na are 4.6% and 3.8%,respectively, and Cu and Al is lower. The dry iron sludge was characterized by XRD and SEM as well. By the acid leaching method was used for molysite recycling from iron mud, and the optimum operation conditions were concluded as follows: sulfuric acid concentration is 4mol/L;solid-liquid ratio(m/V) is 1:4; stirring time 60 min, leaching temperature is 40 ℃. After the acid leaching process, the iron sludge quality decreased by 65.6%, achieving the sludge reduction goals.Sewage coagulation experiment and sludge conditioning experiment shows that the effect of recovery ferric and ferrous sulfate are almost the same. After a cost-benefit calculation, recycling iron possess a certain economical value. |
PDF Full Text Request