Development and application of wastewater treatment system using membrane separation

本课题旨在研究利用膜分离进行固液分离的污水处理工艺。本项目特别注重实践方面，取得了以下成果：(1)膜过滤的特点：采用平板式Uitra膜和微膜，考察活性污泥曝气池与膜组件连接时的过滤阻力和滤液水质。滤液质量与膜的孔径大小无关。过滤速率与曝气池中MLSS无关，对膜孔径不敏感。在曝气池中观察到高分子量有机物的积累。凝胶色谱法测定分子量分布。(2)中空纤维膜在好氧废水处理中的应用：孔径为0。将1 μ m的活性污泥直接浸入实验室规模的曝气池中进行处理。流出物通过这层膜被吸走。连续抽吸造成过滤器堵塞问题，而引入间歇抽吸解决了这一问题。操作成功近一年，MLSS高达40000 mg/L左右。然而，非常高的生物量降低了溶解氧水平，COD去除率显著降低。只要间歇操作，中空纤维膜的应用前景广阔。(3)膜分离在厌氧工艺中的应用：采用平板式膜与混流式厌氧反应器相结合。该系统实现了传统厌氧工艺无法实现的长时间生物质停留。以牛奶为合成底物的实验表明，MLSS可达1.5万mg/L，产甲烷量高，出水质量好。过滤通量逐渐下降，但通过清洗膜可恢复膜。该系统对生活污泥进行了处理。膜法在10天的滞留时间内，甲烷产出量比常规法高出20-40%。研究了聚乙烯醇（PVA）对厌氧细菌的固定化作用。得到的微球在相当长的时间内稳定，并且固定化后的孵育可以提高细菌的生物活性。少

This research project aims at the development of wastewater treatment process in with employing membrane separation for solid-liquid separatikon. This project especially focused on practical aspects and the following results were obtained.(1) Charecteristics of membrane filtration: Uitra membrane and micro membrene in flat type was used to examine the filtration resistance and filtrate water quality when aeration tank of activated sludge was connected with membrane module. Filtrate quality did not at all depend on pore size of membrane. Filtration rate was independent from MLSS in aeration tank, and was not sensitive to pore size of membrane. Accumulation of organic materials of high molecular weight was observed in aeration tank. Molecular weight distribution was examined with gel chromatography.(2) Application of hollow fiber membrane to aerobic wastewater treatment: Hollow fiber membrene of pore-size of 0. 1 micron was directly submerged into laboratoryscale aeration tank of activat … More ed sludge process. Effluent was suctioned through this membrane. Continuous suctioning caused filter clogging problem, while introducing the intermittent suction solved this problem. Successful operation was achieved for nearly one year with MLSS as high as about 40,000 mg/L. However, very high biomass dropped dissolved oxygen level, and COD removal decreased significantly. Application of hollow fiber membrene is very promising as long as intermittent operation is done.(3) Application of membrane separation to anaerobic process: A flat type of membrane was used in combination with mixed-flow type anaerobic reactor. This system enabled long biomass residence time which can not be achieved in conventional anaerobic process. The experiment using milk as a synthetic substrate showad that MLSS reached as high as 15,000 mg/L, and good methane production with excellent effluent was achieved. Filtration flux decreased gradually but the membrene was recovered by cleaning the membrane. Domestic sewage sludge was gtreated in this system. Membrane process can produce 20-40% more methane than conventional process at betention time of 10 days. Immobilization of anaerobic bacteria by using polyvinyl alcohol (PVA) was examined. The obtained beads were stable for reasonably long period, and incubation after the immobilization could raise the biological activity of bacteria. Less