曝气膜生物反应器运行过程中污泥活性特征变化及其对膜污染的影响

研究了曝气膜生物反应器运行过程中活性污泥主要活性特征变化及其对膜污染的影响.通过排出剩余污泥的办法维持活性污泥浓度在4000 mg·L-1左右,并连续运行75 d.运行期间,每日检测活性污泥的各项性质指标便于反映污泥特性的变化.结果表明,随着反应器运行时间的延长,污泥脱氢酶活性逐渐增加,其对反应器的运行有着两方面的作用,一方面会强化微生物对污染物的去除,但另一方面则导致了胞外聚合物的增加,并加速膜污染.而污泥表观产率则随着运行时间的延长先增加后有所减少,其粒径逐渐减小,且胞外聚合物呈现增加的趋势,总的出水水质情况逐渐提高,与此同时,反应器内原生动物及后生动物在运行前期较少,而在后期大量出现.膜污染分析结果表明运行后期膜污染速度明显加快,其原因在于:污泥粒径的减小以及胞外聚合物的增加导致细小颗粒及胞外聚合物堵塞或在膜表面沉积数量增加.

Variations in the Active Characteristics of Sludge During the Operation of an Aerobic Membrane Bioreactor and Their Effects on Membrane Fouling

The present work investigated the variations in the active characteristics of sludge during the operation period of an aeration membrane bioreactor, as well as their effects on the fouling of membrane module. Through discharging the excess sludge, the concentration of the mixed liquor was maintained at around 4000 mg·L^-1 for 75 days, during which the characteristics of sludge were carefully tested every day to reflect its variation. Results indicated the dehydrogenase activity increased with the prolonging operation time. The increased activity of dehydrogenase had two effects on the operation of the bioreactor, one was the enhancement of pollutant removal by the microorganisms, while the other effect was the increase of extracellular polymeric substance (EPS), which led to a deteriorative effect on the membrane fouling. During the operation of the bioreactor, the sludge yield coefficient first increased, and then decreased to a certain degree with obvious decrease in particle size and increase in the amount of EPS, which also enhanced the quality of the effluent. At the same time, protozoon and metazoan were observed in the whole bioreactor at the late operational phase but relatively rare at the initial phase. Analysis of membrane fouling showed that the fouling rate of the membrane module increased during the late operational period, which was attributed to the deposition of fine sludge particles and EPS caused by the decreased particle size of the sludge and the increased amount of EPS.