Study On The Treatment Of Highly Concentrated Dyeing Wastewater Of Cotton Woven Includes Desizing Wastewater

The wastewater discharged from the production process of printing and dyeing enterprises which dyeing of cotton woven fabrics mainly includes desizing, boiled refining, bleaching, mercerizing, dyeing and printing wastewater and so on. To improve the smoothness and wear resistance of the fabric, large amounts of slurry were used in the process of warp sizing. As a consequence, the dyeing mixed wastewater often contains a large number of desizing wastewater with high concentrations of CODCr, strong alkalinity and poor biodegradability, resulting in the serious environmental problems. It seems to be very urgent to exploit an efficient economic and stable technology to ensure the discharge of wastewater meet the emission standards. At the same time, this study possesses very essential realism significance.According to the characteristics of the mixed wastewater and problems in the treatment process, this study converts the current approaches on the treatment of desizing wastewater and then proposes Coagulation Discoloration→Anaerobic Baffled Reactor (ABR)→Contact Oxidation Method→Fenton Oxidation→Biological Aerated Filter (BAF) combined process for advanced treatment of wastewater. The study has investigated the optimal operation parameters in the coagulation pretreatment stage, conventional biochemical treatment stage and depthstandard processing phase. The experimental results are summarized as follows:(1) The optimal reaction conditions for coagulation tests are:the dosage of WH-6 and FeCl2 are 200 and 600 mg/L, respectively. Under the initial pH condition of 12, CODCr decreases from 3600 to 1750 mg/L, whose removal efficiency is 51.5%. The chroma of effluent is 80 times. Besides, the concentration of SO42- is 450 mg/L. The wastewater treatment cost is 0.782-0.818 yuan/t.(2) Using an improved ABR contact oxidation reactor after the coagulation pretreatment, the effluent receives a good CODCr removal efficiency. With the HRT of ABR and Contact Oxidation reactor are 24 h and 20 h, respectively, the CODCr decreased from 1750 to 214 mg/L, whose removal rate is about 87.78%. The BOD5 reduced to 17.1 mg/L. The B/C is about 0.08, which indicates that the wastewater has a poor biodegradability. So it is necessary to have further treatment to meet the discharging standards.(3) A Fenton Oxidation-BAF combined process has been adopted to further treat the above effluent. With the condition of initial pH=4, the concentration of H2O2 is 50 mg/L,ρ(Fe2+)/ρ(H2O2)=0.5, after reaction 60 min, while HRT=2.5 h, then the COD of effluent decreased from 214 to 73.04 mg/L. The removal rate is more than 65%. The chroma reduced to less than 35 fold. This result reveals that the Fenton Oxidation-BAF combined treatment process can achieve high efficiency. The running costs of the process is about 1.15 yuan/t wastewater.(4) Through the advanced treatment includes Coagulation Discoloration→ABR→Contact Oxidation Method→Fenton Oxidation→BAF combined process in proper sequence, the CODCr of the initial wastewater decreased from 3600 to 73.04 mg/L, i.e. the removal rate is 98%. While the chroma reduced from 1000 to 35 fold, which removal efficiency is 99% approximately. The final effluent quality is better than the discharging standards. The whole running costs for this technique is about 2.5 yuan/t, which suggest that it is a cost-effectively solution for the wastewater emission problems.