Technical Research On Pretreatment To Improve BOD5/CODcr Of Printing And Dyeing Wasterwater

The purpose of this study is to improve the biodegradability of dyeing and printing wastewater through the pretreatment. This study takes BOD5/CODcr (hereinafter referred to as "B/C") as main investigation index, takes field test and quantitative analysis as the main research method, explore the possibility of raising B/C under the treatment of physicochemical method and physicochemical-biochemical method, and the advantage of them. Physicochemical method mainly includes Fenton oxidation, ferrous sulfate coagulation method. Physicochemical-biochemical method mainly refers to the synergy effects of ferrous sulfate coagulation method and ABR reaction pond.Fenton oxidation process treats with printing and dyeing wastewater, when hydrogen peroxide and ferrous sulfate's Moore dosing ratio (n (H2O2)/n (Fe2+)) is between 5-10, H2O2 dosage is between 1.3-2.5 mmol/L, reaction time is between 20-30 min, initial pH is between 3-5, the COD removal rate can stabilize in below 40 percent, and the B/C can be improve to 0.3 above. In this operation condition, this reaction can both reduce COD load in a small degree for the subsequent processing, and improve B/C to 0.3 above.Ferrous sulfate coagulation method processes printing and dyeing wastewater, when ferrous sulfate dosage is 500mg/L, initial pH is 10, reaction time is 5min, adjusting pH to 10, precipitation time is 60min, the ratio of B/C basic maintaining at 0.3 above, and the preprocessing COD removal rate would below 40 percent.Through technology and economic comparison, this study thinks ferrous sulfate coagulation process is more suitable for preprocessing section, and selects ferrous sulfate coagulation process as the main technology for pilot test.In the pilot test with ferrous sulfate method running separately, no pH value adjustment, ensuring precipitation time 60min, ferrous sulfate dosage is 300ppm,400ppm, 500ppm, B/C then can ascend to 0.18-0.33, and for COD removal rate 20% to 30%.The treatment results of physicochemical-biochemical method are in better shape than both run separately.The study is the research project of the subproject(the study on spot informantion survey and sewage farm pretreatment technology) of the major science and technology project on national water body pollution control and treatment(the study on water environment management technology in water town and integrated demonstration) during 11th Five-year plan. (subproject:No.2008ZX07313-006-02)...