| Leachate from sanitary landfill is a high concentration organic effluent whose composition is complicated and its quality and quantity is fluctuant wildly. If the garbage leachate is not treated properly, it will seriously contaminate the soil, groundwater and surface water and even air, causing a secondary pollution. Therefore, landfill leachate treatment is still a worldwide problem.Leachate from sanitary landfill is a high concentration organic effluent with a high chemical oxygen demand(COD) and ammonia(NH3-N) concentration, but low carbon-nitrogen ratio and BOD5/COD( B/C). So the current research is focused on physical and chemical methods, especially with the reverse osmosis membrane. Landfill leachate used in this study were taken from the Li Ling sanitary landfill located in Zhu Zhou, Hunan province, south of China and was treated with innovative radiation channel disc tube reverse osmosis(RCDTRO) system. Its performance was evaluated by removal efficiency and membrane fouling resistance. Besides, a bench-scale experiment was conducted to determine the optimal operating conditions. Finally, fouled membrane was detected by scanning electron microscopy(SEM) and cleaned by ultrasonic wave. These results revealed the major mechanism of fouling, and provided scientific evidence for RCDTRO system operation.In this paper, the performance of RCDTRO for leachate treatment was evaluated from organics removal efficiency and membrane fouling resistance(cycle). It was found that the removal rate of COD and NH 3-N was 98.89±0.26% and 96.04±0.21% respectively, and desalination rate was 97.53±0.18% for the single-stage RCDTRO system without any pre-treatment or post-treatment. Besides, longer cleaning cycle suggested strong membrane fouling resistance of the RCDTRO system. A bench-scale experiment was conducted to determine the optimal operating conditions, where the speed of pressuring pump was 35 Hz, recovery rate was 65% to 75% and operating pressure was 42 bar to 50 bar. The experimental results demonstrated that RCDTRO system was technically and economically applicable for the treatment of landfill leachate, meanwhile could maintain high treatment efficiency at relatively low pressure.The composition of the reverse osmosis membrane surface pollutants were analyzed by SEM. The fouling membrane were cleaned by the organic solvent of acetone and the surface layer change at different time was analyzed. Simultaneously, the fouling membrane also was cleaned by the ultrasound and the composition of surface material before and after cleaning w as studied. Finally, to further determine the reverse osmosis membrane surface pollutants ch anges before and after cleaning, the membrane surface roughness before and after cleaning using AFM-electronic force microscope. Conclusions were followed:(1) A large number of organic matter and heavy metals, non-metallic elements mainly including silicon and sulfur elements gathered on the contaminated reverse osmosis membrane surface.(2) The metal elements, mainly mercury, copper, iron, which were formed colloidal substance in water, adhesive on the membrane surface.(3) The formation process of membrane pollution could attributed to heavy metals or materials such as silicon which were formed colloidal substance and adhesive on the membrane surface, and then co nstantly adsorbed organic matter, the organic matter and colloid chelate.(4) Reverse osmosis membrane fouling,which immersed in organic solvent of acetone, could be reduced the concentration of the surfac e material of membrane fouling, especially organic matter.(5) The fouling reverse osmosis membrane could effectively reduce the organic pollution and reduce the membrane surface roughness, increasing its smoothness after ultrasonic cleaning. |
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