Chiemchaisri C, Yamamoto K
Department of Environmental Engineering, Kasetsart University, 50 Phaholyothin Road, Chatuchak Bangkok 10900, Thailand.
Water Sci Technol. 2005;51(10):85-92.
Biological nitrogen removal in a membrane separation bioreactor developed for on-site domestic wastewater treatment was investigated. The bioreactor employed hollow fiber membrane modules for solid-liquid separation so that the biomass could be completely retained within the system. Intermittent aeration was supplied with 90 minutes on and off cycle to achieve nitrification and denitrification reaction for nitrogen removal. High COD and nitrogen removal of more than 90% were achieved under a moderate temperature of 25 degrees C. As the temperature was stepwise decreased from 25 to 5 degrees C, COD removal in the system could be constantly maintained while nitrogen removal was deteriorated. Nevertheless, increasing aeration supply could enhance nitrification at low temperature with benefit from complete retention of nitrifying bacteria within the system by membrane separation. At low operating temperature range of 5 degrees C, nitrogen removal could be recovered to more than 85%. A mathematical model considering diffusion resistance of limiting substrate into the bio-particle is applied to describe nitrogen removal in a membrane separation bioreactor. The simulation suggested that limitation of the oxygen supply was the major cause of inhibition of nitrification during temperature decrease. Nevertheless, increasing aeration could promote oxygen diffusion into the bio-particle. Sufficient oxygen was supplied to the nitrifying bacteria and the nitrification could proceed. In the membrane separation bioreactor, biomass concentration under low temperature operation was allowed to increase by 2-3 times of that of moderate temperature to compensate for the loss of bacterial activities so that the temperature effect was masked.
研究了用于现场生活污水处理的膜分离生物反应器中的生物脱氮过程。该生物反应器采用中空纤维膜组件进行固液分离，以便使生物质能完全保留在系统内。采用90分钟开/关循环的间歇曝气来实现硝化和反硝化反应以去除氮。在25℃的适中温度下，化学需氧量（COD）和氮的去除率均达到90%以上。当温度从25℃逐步降至5℃时，系统中的COD去除率可保持稳定，而氮的去除率则下降。然而，增加曝气供应可在低温下增强硝化作用，这得益于膜分离使硝化细菌在系统内得以完全保留。在5℃的低运行温度范围内，氮的去除率可恢复至85%以上。应用一个考虑了限制底物向生物颗粒扩散阻力的数学模型来描述膜分离生物反应器中的氮去除过程。模拟结果表明，温度降低期间硝化作用受到抑制的主要原因是氧气供应受限。然而，增加曝气可促进氧气向生物颗粒内扩散。向硝化细菌提供了充足的氧气，硝化作用得以进行。在膜分离生物反应器中，低温运行时的生物质浓度可提高至适中温度时的2至3倍，以补偿细菌活性的损失，从而掩盖了温度的影响。
