Research On COD Removal And Decolorization Of Textile Effluent

Textile and dying industry have developed for more than one century, which is one of the most historical national industries in our country, and play a very important role in the national economic development. However, there is a lot of wastewater discharged in processes of printing and dying. If treated in unproper way, textile effluent would not only cause great damagement of ecological environment, but also have adverse effects on local people's physical health. Therefore, it is meaningful to get an efficient and economical method for treating textile effluent.In this work, COD removal and decolorization of polyester scour effluent have been studied experimentally. The effluent was derived from a textile plant in Zhejiang. The dark brown wastewater has properties of the pH value of 13.7, the chemical oxygen demand (COD) of 6800mg/L, the chroma of 1000 times, and the suspended solids (SS) concentration of 210mg/L. There exists a surface active agent (SAA) of fatty alcohol-polyoxyethylene ether (AEO) in the wastewater. The main processes of the wastewater treatment are as follows:acidulated bentonite chemical-coagulate in the initial treatment, O3/UV advanced oxidation processes (AOPs) in the secondary treatment, and fly ash adsorption in the final treatment. An orthogonal table was used to find out the impact of dosage of BNT and polyacrylamide (PAM), stirring time, pH value after acid out on the removal of COD and color during the coagulation phase. After the initial treatment, the sample was treated by O3/UV under different pH value and aeration time. Fly ash was used as an absorbent before the treated wastewater was discharged, and another orthogonal table was used to study the impact of pH value, dosage of fly ash, reaction time on the adsorption effect. Finally, the optimum treatment conditions have been summarized.The valuable results and main conclusions are as follows:(1) For treating 50ml wastewater, the optimum coagulation conditions are to add 0.25g bentonite and 0.5mg PAM, the stirring time is 10min, and the pH value is 2 after acid out. The removal efficiencies of COD and color are 79.7% and 90%, respectively.(2) During the AOPs stage, the COD removal fluctuates over with time. When the pH value is adjusted to 8, the removal efficiency of COD is about 11% after 50min oxidation. There is no decolorization effect under various pH value and oxidation time.(3) For treating 50ml wastewater, the optimum adsorption conditions are to adjust the pH value to 2 and add 2g fly ash under the stirring time of 30min. The removal efficiencies of COD and color are 45% and 75%, respectively.(4) In the whole process of the treatment, the COD value and the chroma of wastewater sample are reduce to 675.7mg/L and 25 times, respectively, and the total efficiencies of COD removal and decolorization are 90.6% and 97.5%, respectively.