Study On Print And Dye Wastewater Treatment By Coagulating Sedimentation-Hydrolytic Acidification-Membrane Bioreactor Coulping Process

At present, the printing and dyeing wastewater is one of the most difficulty treated wastewater in industry wastewater. In this paper, the coulping treatment process of sedimention – hydrolytic acidification – membrane bioreactor was carried out on the printing and dyeing wastewater. The influence of each process opreating conditions on the treatment effeciency was investigated. The main results are as follows:(1) The printing and dyeing wastewater was treated by coagulation sedimentation process. FeCl3 was used as coagulant. When the dosage of FeCl3 is more than 500 mg/L, the removal rate of both COD and chroma increased insignificantly. The FeCl3 dosage of 500 mg/L was considered as the best dosage. The COD removal rate is 55.3% and the chroma removal rate is 68.8%. In addtion, the pH value of 8.0 was choosed as the final pH value due to the hydrolysis acidification process as the further treatement process.(2) In the hydrolysis acidification process, 12 h of hydraulic retention time, 4850 mg/L of sludge concentration, 6.5 ~ 8 of pH value, 20 ~ 30 ? of operating temperature were choosen as the optimal operating conditions for 2 months stably operating. The average effluent COD was in the range of 300 ~ 360 mg/L. The value of B/C increased from 0.270 to 0.354. The biodegradability of the wastewater was improved.(3) The hydrolysis acidification effluent was treated by effluent membrane bioreactor(MBR). The COD removal rate reached more than 80% under the optimal operating conditions of MBR(7000 mg/L of sludge concentration, 12 h of hydraulic retention time, 4 mg/L of dissolved oxygen concentration).(4) The coupling process of sedimention – hydrolytic acidification – membrane bioreactor was carried out in long-term by using the optimization conditions of each process. The quality of effluent was stable and reached the indirect emission standard of ?Discharge Standard of Water Pollutant for Dyeing and Finishing of Textile Industry ?.(5) The structures of the coulping process were designed for the daily average of 2400 tons of wastewater. The operating cost was about 1.95 yuan per ton wastewater by estimating.