Study On Advanced Treatment Of Printing And Dyeing Wastewater By Micro Electrolysis-fenton Oxidation Combined With Biological Treatment

Textile printing and dyeing industry occupies an important position in China's economic structure.Its emission is a kind of typical organic wastewater which has high pollution and high chroma.When the printing and dyeing wastewater which was not treated properly is discharged into the natural water body,it could destroy the natural environment and seriously threatens the health of human beings.The quality and quantity of dyes in dyeing and printing industry have been improved over the years and the synthetic process has been improved several times,these lead to the complex structure of dye molecules and the difficulty of wastewater treatment.In 2015,the modified version of "Discharge Standard Of Water Pollutants For Dyeing And Finishing Of Textile Industry"(GB4287-2012)was released,it improves the emission standard of printing and dyeing wastewater.The printing and dyeing wastewater treated by biological oxidation process has been unable to meet the emission requirements.In this experiment,the physical and chemical methods combined with biochemical treatment technology were used for the advanced treatment of printing and dyeing wastewater in order to solve the limitation of existing technology.With a series of experimental researches carried out,the parameters of printing and dyeing wastewater treatment process were optimized,which would provide theoretical basis and practical guidance for practical engineering design and application.In this experiment,the micro electrolysis-Fenton oxidation process was used to treat the dyeing wastewater.Through the single factor influencing experiment,Optimum reaction conditions of the experiment were found for the pretreatment of micro electrolysis:the ratio of iron to carbon was 2:1,pH:5,the retention time was 120 minutes.The Fenton oxidation was used to retreatment the wastewater from micro electrolysis in order to oxidize the organic compounds in wastewater.The azo bond and the double bonds of the chromophoric group were destroyed and broken after the treatment of Fenton,the biodegradability was significantly improved.Through the single factor influencing experiment,the best conditions found for the pretreatment of Fenton oxidation were as follows:the dosage of H2O2 was 8 mL/L,the dosage of FeSO4·7H2O was 1.0 g/L,the pH value was 4 and the retention time was 120 minutes.After the pretreatment of micro electrolysis-Fenton oxidation,the COD of effluent was 750 mg/L,the removal rate of COD was 57%,the chroma of effluent was 10 times,and the B/C was increased to 0.33.After pretreatment,there was still a certain concentration of pollutants in dyeing wastewater.Dyes and intermediates can strongly inhibit the activity of microbial,The effluent was difficult to meet the emission standard with the treatment of aerobic biological treatment.In this experiment,hydrolysis acidification process was used for the last step before biochemical treatment.Single factor influencing experiments were carried out to establish the best process parameters.The best conditions were found for the hydrolysis acidification process were as folllows:the influent pH was 6.5,the retention time was 12 hours.Under this condition,the concentration of VFAs could reach to 720 mg/L and the rate of hydrolytic acidification was 11.43%.In order to achieve the discharge of wastewater,the biochemical system was used for the final treatment.In this experiment,the biological contact oxidation was used to treat the effluent of pretreatment process.Biological contact oxidation process was started by the method of feeding and culture.In this process,a lot of sludge was growing and the color of the biofilm was light yellow.Microbes were clustered together and formed a fibrous community,then attached to the surface of the filler.In the experiment,the treatment of dyeing wastewater by biological contact oxidation process under different operational condition was studied.The best conditions were found for the biological contact oxidation were as follows:the retention time was 12 hours,the ratio of gas and water is 28:1.Under this condition,the effluent COD could reach 100 mg/L,the pollutant in wastewater was removed basically.