The Study On Membrane Pollution And Cleaning Methods During Recovery Of HS From MBR Effluent Of Leachate By UF

The Sanitary Landfill is the main treatment technology for municipal waste disposal currently. Landfill leachate, produced in the process of landfill disposal, contains high concentration of organic substances. It is usually considered that the difficulty of leachate disposal is resulted from the following factors :the fluctuation of water quality and quantity, the decrease of BOD/COD ,the high concentration of ammonia and the imbalance of nutriments. But recent studies have shown that the fundamental reason is the presence of a large amount of Humic Substances (HS),even after the microbial treatment.Membrane Bioreactor(MBR) is gradually applied to the leachate treatment in recent years, for example in Beijing, Shanghai and Chongqing etc. But Nanofiltration (NF) or Reverse Osmosi(sRO) has to be used to further remove the pollutants and make the effluent meet the emission requirements. Separation and recovery of HS from MBR effluent by Ultrafiltration Membrane(UF) is not only the further treatment method ,but also a way to recover the HS . It can considered to substitute for NF and RO. Separation of HS from leachate by UF has been proved to be feasible. This paper focuses on the UF membrane fouling behavior and cleaning method in the process of separation and recovery of HS from MBR effluent. It focuses on several index, such as temperature, pressure, flux change, membrane resistance and membrane cleaning effect. The experimental material is from BeiShenShu landfill in Beijing. Sequence batch is applied in the experiment and the biggest concentration factor (CF) is 5 .Samples are got at times including different CFs . Pressure ranges from 0.3MPa to 0.7MPa. Main experimental results are in the following:1. Fresh water flux and temperature change linearly while flux of MBR effluent and temperature change exponentially Through experimental analysis, the formulars under different pressures are got.2. Flux dramatically increases with the rise of pressure ,but the flux under 0.7MPa is almost the same with flux under 0.6MPa. 0.6MPa is the critical pressure. Unit consumption of energy decreases with the rise of pressure.But the unit comsuption of energy under 0.7MPa is higher than that under 0.6MPa. The smallest unit consumption of energy is under 0.6MPa.3. The concentration of organic matter and HS increase greatly with the rise of CF but the ratio of HS to organic matter varies with pressure. The ratio of HS to organic matter gets to about 90% when CF is 5 under the pressure of 0.4MPa, 0.5MPa and 0.6MPa,but only 60% which is lower than that of the feed at 0.7MPa.The metal ions don't concentrate in the retentate under any pressure.4. The membrane resistance consists of resistance resulted from the membrane itself and pollutants ,in which the latter is only a small part ,nearly 10%~20% of the whole .The resistance resulted from pollutants rises quickly at 0.7MPa.5. Concentration polarization and inorganic scale, instead of microbial adsorption ,are the two main factors which cause membrane to be polluted .Hydrocleaning and acid-cleaning are much more efficient than alkali-cleaning. The recovery ratio of flux after hydrocleaning,acid-cleaning and alkali-cleaning is 99.5%. Through experiments, the recommended procedure of cleaning contains 30 minuts of hydrocleaning ,50 minutes of acid-cleaning and 50 minutes of alkali-cleaning .If the membrane is heavily polluted , it will need 1h~2h soak period in the acid or alkali.