Processing Sugar Wastewater And Membrane Fouling In Membrane Bioreactor Cleaning

Strong waste water produced in the sugar industry contains a large number of organic pollutants .Without a firm and complicated treatment, direct discharge of this kind of waste water into surrounding environment water bodies would cause serious pollution.At present, a major treatment technology for waste water produced from sugar refinery is aerobic biological method, and its process mainly contains two steps, physical chemistry pretreatment and biochemical disposal system for advanced treatment.A conclusion of the major problem of the sugar refinery waste water treatment, based on lots of field research and literature review, is how to choose a more economical, reasonable, and steady waste water treatment technology. After study and discussion, this sugar refinery waste water treatment experiment was conducted by using membrane bioreactor technology as its core treatment process.During the experiment, the test reactor operation was optimized through control of the operation parameters such as dissolved oxygen concentration (DO), hydraulic retention time (HRT), and sludge concentration (MLSS). Meanwhile, changes were tracked by monitoring effluent COD, NH₄⁺-N, total nitrogen, and total phosphorus. After a long time stable operation, the test result is concluded as following:(1) The membrane bioreactor runs steadily during the treatment of sugar wastewater with large amounts of organic carbon in it, and the effluent is good.(2) After test and study, established the circumstance under which the effluent of membrane bioreactor will be the best, that is oxygen concentration, hydraulic retention time respectively in 5 6 mg/L, and 20 hours.(3) When MBR is in stable running, COD removal can reach 91.13%, NH₄⁺-N removal is 90.84%, TN removal rate can reach 84.74%, TP removal can reach 62%, and it has no odor.(4) Based on the analysis of the membrane resistance, we know that formation of cake layer is the major cause of the membrane fouling, cake layer resistance makes up 81.21% of total resistance.(5) During the test, we used three kinds of chemical solution to clean the fouled membrane, 0.1% sodium hypochlorite, 0.1% hydrochloric acid, and 0.1% sodium hydroxide solution. It is concluded after comparison of their cleaning efficiency, 0.1% sodium hypochlorite has the best performance, flux recovery rate can reach more than 90%. 0.1% hydrochloric acid has less efficiency, and 0.1% of sodium hydroxide has the minimum.