A Experimental Research Of Treating Rare Earth Ammonia Wastewater By A Submerged Membrane Bioreactor

With the development of rare earth industry, the emissions of Rare Earth (RE) wastewater are increasing and are difficult to deal with it, so a suitable technology path needs to be found urgently. And Membrane bioreactor (MBR) is a new water treatment technology, which is the combination of an efficient membrane separation and activated sludge. It can be applied to treat the high concentration organic wastewater that was not only to remove nitrogen, but also was structure reasonable, small footprint and without the secondary settling tank. The wastewater is treated by the bioreactor which is feasible, and is more appropriate treatment process.The UASB treated water was mainly as raw water in this paper. The wastewater was studied by the bioreactor. The treatment effect and the kinetic parameters were analysised, and the cleaning method was determined.The start-up of reactor were mainly the cultivation and domesticated of sludge, using glucose as nutrient medium, which made sludge proliferated, and gradually increased the concentration of ammonia water, kept the sludge in the lower C/N conditions, to achieve better removal effect. After a month, sludge concentration didn't change, and when the C/N was 0.87, removal efficiency of COD was stable, which was about 85%, ammonia nitrogen removal was up to 50%.During the operation, the removal of reactor was investigated with the load increased. COD and ammonia removal were influenced by pH, dissolved oxygen, hydraulic retention time (HRT).And the best experimental conditions were: HRT was 10, pH = 7.5, dissolved oxygen : 3mg/L, The removal rate of COD and ammonia nitrogen were 88.7% and 54.6%.The kinetic analysis showed that the bacterial specific growth rate and substrate concentration equation was satisfied monod equation: , maximum specific degradation rate was 0.012d_-1, substrate saturation constant was 23.47mg/L, digestion kinetic model can be expressed as: .In order to ensure better operation effect, it was required to clean the membrane to reduce membrane blockage. First of all, physical cleaning was used. About 15 minutes was used by water washing, then one hour was used by backwash water, flux could be recovered of 20.9%. Secondly the NaOH was used, cleaning concentration was 0.25%, cleaning time was 30min, the temperature was 40℃,flux can be recovered more than 70%.