Coagulation-Hydrolysis Acidification-Contact Oxidation Treatment Of Automotive Paint Wastewater

In recent years,the rapid development of the automotive industry has gradually become an important part of China's industrial development.In the process of car painting,a large amount of waste water is generated.If it is not disposed of in a reasonable manner and it is directly discharged into the environment,it will cause serious damage to the environment.In this project,we used the paint wastewater from an automobile factory to conduct experiments to investigate the treatment effect and influencing factors of the coagulation-hydrolysis acidification-contact oxidation method.The paint wastewater is generated when the air in the work area of the spray booth is washed,and the paint mist in the air reacts with the organic solvent and is transferred to the water.The paint wastewater contains a large amount of paint mist particles and harmful substances such as paint films,pigments and powders,etc,and the water quality changes largely.This experiment mainly explored the treatment effects of COD,SS,NH4~+-N and TP in wastewater by the coagulation-hydrolysis acidification-contact oxidation process,and analyzed and compared the effects of different HRT and DO concentrations on the test results,determing the best conditions for treating such wastewater.Finally,COD,SS and NH4~+-N of the effluent quality reached the Class I B standard of the“Pollutant Discharge Standard of Urban Wastewater Treatment Plants”(GB18918-2002),and TP reached the Class II standard.First,we could determine the optimal conditions of the coagulation test through multiple sets of single-factor tests.The test results showed that when using the PAC as a coagulant,PAC dosage of 80mg/L,stirring intensity of 300r/min,reaction time of 60min,ambient pH of 8 to 9,the removal rates of COD and SS were up to 87.3%and 89.6%.Second,the coagulated wastewater is treated by biochemical methods,namely hydrolysis acidification-contact oxidation.The basic flow was:the coagulated supernatant was pumped into the anaerobic environment,which is the hydrolysis and acidification reactor,through the air pump,and then into the aerobic environment,which is the contact oxidation reactor.COD,NH4~+-N and TP in the wastewater was treated by combining anaerobic and aerobic methods.First,through the domestication of sludge,a reactor membrane test was performed.A total of 15 days for the start-up of the membrane-initiating experiment were completed.On the 12th to 13th days,the hydrolysis and acidification reactor was successfully detached;On the 10th to 11th days,the contact oxidation reactor was successfully detached.During the startup of the membrane,the removal rates of COD in the hydrolysis acidification reactor were 49%;During the startup of the membrane,the removal rates of COD,NH4~+-N and TP in the contact oxidation reactor were 89.5%,96.9%and 93.7%,respectively.In order to explore the influence of operating parameters on the test results,multiple sets of tests were designed to study the influence of HRT and DO concentrations on the test results.The hydraulic retention time of the control system was 6h,9h,12h,15h,and the best HRT was obtained from the analytical test results.Based on the best HRT,explore the effect of different DO concentrations further in the hydrolysis acidification and contact oxidation tanks on the test results.The DO concentration in the anaerobic tank which is hydrolysis and acidification reactor was 0~0.2mg/L,and the DO concentration in the aerobic tank that is the contact oxidation reactor was 1~2mg/L,2~3mg/L,3~4mg/L,respectively.Analyze the test results to the optimal DO concentration.After several sets of test analysis,comprehensive energy consumption,economical and other factors,the best HRT for the appropriate test run was 12h,and the removal rates for COD,NH4~+-N,and TP were 77%,83%,and 88%,respectively.The optimum DO concentration was 3 to 4 mg/L,and the removal rates of COD,NH4~+-N,and TP were 89%to 92%,89%to 94%,and 74%to 77%,respectively.The tests showed that the use of coagulation-hydrolysis acidification-contact oxidation method for the treatment of automotive paint wastewater had the stability of the effluent,good economy,and positive significance for the environment,society,businesses and so on.