摘要
一体式膜生物反应器是新型的污水处理工艺,其膜污染控制是一体式MBR应用的关键。本文研究了一体式膜生物反应器中膜污染过程及膜污染控制方法,分析膜污染的机理,探索有利于一体式MBR长期运行的有针对性的膜污染控制技术。研究表明,在一体式MBR膜过滤总阻力中,沉积层阻力占主导地位,是膜过滤过程膜污染的主要来源,长期运行产生的微生物污染也不可忽视,所以一体式MBR的膜污染防治应围绕如何有效控制沉积层的积累和微生物污染;为了优化反应器的水力条件,运行中采用曝气冲刷、间歇抽吸的工作方式,并确定了最佳曝气量、抽吸时间和周期,对减缓沉积层的积累和膜通量的下降具有较好的效果;通过较长时间持续曝气来进行水力清洗在一段时间里控制了污泥向膜面的对流传递过程,而持续的曝气增强了反扩散作用和膜面的传递作用,可以达到一定的恢复通量的效果;对比普通活性污泥法MBR和生物膜MBR,后者可以有效降低膜内外COD的浓度差,控制生物反应器中优势污染物的积累,进而减缓膜通量下降的趋势;对比帘式膜组件和串式膜组件,由于帘式膜组件中空纤维膜丝垂直布置,膜丝之间的混合液可以更好地受到曝气扰动的影响,因此比串式膜组件的抗污染能力要强;针对膜的生物污染,采用次氯酸钠化学清洗的方法效果很好,可以有效去除膜面有机物及细菌污染。
Submerged membrane bio-reactor is a latest wastewater treatment process and membrane fouling control is the key to its spread. In the paper, the membrane fouling process and fouling control methods for a submerged membrane bio-reactor were studied. At first, the mechanism of membrane fouling was analyzed. Then, pertinent membrane fouling control countermeasures to facilitate long-term operation were investigated. The experiments showed that the cake layer resistance was dominant among the total trans-membrane resistance and was the main source of membrane fouling. Microorganism contamination could not be neglected in long-term operation. Therefore, membrane-fouling control should focus on effectively control the accumulation of cake layer and microbes. In order to optimizing the hydraulic condition in the reactor, constant aeration and intermittent pumping was conducted and optimal aeration quantity, pumping
period and pause period were identified which could slow down cake layer accumulation and flux decline. Hydraulic rinse through constant aeration could hold the convection transfer from the sludge mixture to membrane surface and boost up the counter-diffusion and transfer along the membrane surface so that flux could be recovered to a certain degree. By comparing MBR combined with conventional activated sludge system and bio-film system, the latter showed its advantage in reducing the COD concentration difference between the outside and inside of the membrane, resisting the accumulation of dominant contaminants and relaxing the trend of flux decline. As to different membrane module styles, the flat module was more tolerant to membrane fouling than bunch module since the former was easy to have its hollow fibers and mixture among them vibrant with the disturbance of aeration. To control the microbe contamination, chemical cleaning
using sodium hypochlorous had satisfactory result for eliminating organic and bacteria contamination.
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