A Study On The Treatment Process Of Chlorinated Methanes Of Chlorinated Polypropylene Production Wastewater

Chloromethane wastewater is characterized by high biotoxicity,difficult natural degradation,long cycle of environmental harm and carcinogenicity.The paper set the wastewater as the research subject,and take advantage of low p H value and high iron ion content of wastewater,use the combination technology of“zero-valent iron reduction-fenton oxidation-chemical precipitation”in the treatment of wastewater to reduce its content of chloroform and carbon tetrachloride so as to make the tail water meet both the discharge standard of pollutants for petrochemical industry（GB31571-2015）and the acceptance standard of sewage treatment plant in a chemical industrial park in Jinchang.The main contents of the paper are as follows:（1）The industrial wastewater temperature of the experimental wastewater is 20°C,and the p H is 0.30-0.35.The content of trichloromethane is 50.45-53.27 mg/L and that of carbon tetrachloride is 1.07-1.32 mg/L.Besides,the content of iron ion is 2.385-2.397 g/L.（2）The paper uses the zero-valent iron reduction process treat the wastewater,and explores the factors affecting the removal effect of trichloromethane and carbon tetrachloride.The optimal combination of factors is determined as follows:the iron powder dosage was 8 g/L,the iron powder particle size was 120 mesh and the reaction time was 10 h,when the removal rate of trichloromethane in the wastewater can reach 92.48%,and the carbon tetrachloride in the wastewater can also meet the discharge standard.It is determined that the process of degradation of trichloromethane by zero-valent iron reduction technology follows the second-order reaction kinetics.Moreover,the degradation of carbon tetrachloride and trichloromethane is accompanied by the production of some reduction products that is dichloromethane,which need to be treated later.（3）Dichloromethane appears in the wastewater treated by zero-valent iron reduction process.The subsequent treatment of dichloromethane and trichloromethane is carried out by Fenton oxidation process.The removal effects of various factors on dichloromethane and trichloromethane are discussed respectively.The optimal combination of factors is determined as follows:p H was 5,the H₂O₂ dosage was 40ml/L,and the reaction time was 1 h,when the removal rate of dichloromethane in the wastewater can reach 82.16%,which meets the discharge standard,and the removal rate of trichloromethane can reach 86.91%.（4）Finally,the wastewater,after zero-valent iron reduction and Fenton treatment,was sedimentated to further reduce its content of trichloromethane to eventually make the dichloromethane,trichloromethane and carbon tetrachloride in the wastewater all meet the discharge standards.