| Pesticide wastewater has become one of the most difficult organic high pollution wastewater treatment problems because of its toxic substances, high concentrations of organic matter, high salt content, complex composition and variation in properties which lead to unsatable water quality and quantity.According to the characteristics of the research object, a pesticide chemical plant mesotrione wastewater, this paper works on a project to explore a more feasible wastewater treatment method, and ultimately determines the composition process using ferrous sulfate complex precipitation-H2O2 cyanide oxide digestion-three-effect evaporator + iron oxide + carbon micro electrolysis-Fenton coagulation + biochemical process to treat mesotrione waste water. The test shows that by using the method, after a strong chemical oxidation process, the toxicity of the wastewater decreases and biodegradability increases, so that the wastwater can ultimately reach the discharge standard by biochemical process.For tis high concentrations of cyanide-containing, this paper uses ferrous sulfate complex precipitation-H2O2 cyanide oxide digestion-three-effect evaporator pretreatment process.The optimal experimental conditions oxidation of ferrous sulfate complex precipitation-H2O2 are : ratio of FeSO4 · 7H2 O actual dosage and theory dosage is 1.3(the theory dosage is 4.32g/L), reaction time is 1.5h, The reaction pH value is between 5 and 6; the 30% H2O2 dosage is 8ml/L, the reaction pH is between 5 tand 6, the reaction time is 3h. Under the reaction conditions, after the process, the Total Cyanide of the wastewater can reduce from 810 mg/L to 13mg/L,with a removal rate of 98.4%; the chroma fell to 400 with a removal rate of 86.7%. COD is about 12000 mg / L, total salt content is about 170000 mg/L. After the three-effect evaporation desalination process, the quality of the wastewater is: the total cyanide is 6 mg/L, COD is about 1300 mg/L, chroma is 50, pH value is 8. After the homogenization with other wastewater, The total cyanide can decrease to 0.15 mg/ L,which can ultimately reach the discharge standard.Under the the reaction conditions, which the pH value is between 2 and 3 and the reaction time is 4 hours, the COD of the wastewater can reduce from 2320 mg/L to 1620mg/L, COD removal rate is about 30.2%, through the iron-carbon micro-electrolysis.The wasterwater still has a great oxicity with a high concentration of pollutants.The Feton is formde by mixing the Fe2+ from the filtrate of the iron-carbon micro-electrolysis and the hydrogen peroxide. The optimum conditions of Fenton oxidation are: the dosage of 30% H2O2 is10 ml / L, pH value is 3, the stirring time is 2h, COD of the wastewater can dropp from 1620 mg/L to 1030mg/L, the COD removal rate is 36.4%.After the homogenization between the wastewater after feton process and the domestic sewage, the mixd wastewater will be treated by coagulating sedimentation.And the optimum conditions of this are: the dosage of PAC is 120mg/ L, the dosage of PAM is 8mg/L, stirring time is 30 min. Under the reaction conditions, the COD of the wastewater can drop from 620 mg/ L to 428mg/L, the COD removal rate is 31%.After being treated by combination of wastewater pre-treatment process, the wastewater can be Non-toxic and harmless, which lead to a higher Biodegradability. Therefore,the wastewater can reach the first degree discharge standard then through subsequent hydrolysis acidification and aerobic biological deep treatment.According to the treatment effect and economic costs, the study shows that the combined process to treat mesotrione wastewater is effective and technically, economically feasible.And the combined process of this study is valuable in engineering application, which can provide a reference guide for other types of refractory wastewater. |
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