Study on Treatment of Printing and Dying Wastewater by Combined Process of Tubular Membrane Bioreactor

A combined process of coagulation-sedimentation/hydrolysis-acidification/separation tubular membrane bioreactor was studied for treatment of printing and dyeing wastewater in the experiment. The influence of main factors in each unit of the combined process on removal effect of pollutants was discussed, and the results showed that for simulated printing and dyeing wastewater Polymeric Aluminum Chloride was the best coagulant and under the dosage was 50 mg/L removal of Chemical Oxygen Demand and colority was 19.6% and 81% respectively. In hydrolysis-acidification unit hydraulic retention time can significantly affect removal of colority in stead of anaerobic sludge concentration, when hydraulic retention time was 16 h and anaerobic sludge concentration was 8 g/L colour removal was about 76%, compared with which Chemical Oxygen Demand removal was lower (only 42%). For separation tubular membrane bioreactor unit, the optimal condition was that mixed liquor suspended solid was 8 g/L and hydraulic retention time was 8 h, and under this condition removal of Chemical Oxygen Demand and colority was 82% and 80% respectively. Analysis of contributions to pollutants removal for each part of tubular membrane bioreactor unit suggested that Chemical Oxygen Demand removal mainly depended on biodegradation of aerobic reactor (59%), and membrane filtration enhanced and stabilized the removal effect (about 23%), but there was no big difference in colority removal for aerobic reactor and membrane filtration unit (separately 42% and 38%).