Membrane fouling is the major problem that hinders the practical application of membrane bioreactor (MBR) systems. Since the MBR system includes living microorganisms and their metabolites, the fouling mechanism is even more complex than that of conventional membrane separation processes. This paper provides an improved understanding of the influence of filamentous bacteria on membrane fouling in microfiltration of activated sludge wastewater. In order to make clear the membrane fouling mechanism of filamentous bacteria, the physicochemical characteristics of sludge flocs, including extracellular polymeric substance (EPS), zeta potential, relative hydrophobicity (RH) and floc morphology were systematically investigated. The results showed that the sludge flocs with negligible filamentous bacteria led to severe membrane pore blocking, and the sludge flocs with filamentous bacteria created the formation of a non-porous cake layer on the membrane surface. The excess growth of filamentous bacteria resulted in much more release of EPS, lower zeta potential, higher hydrophobicity of sludge flocs and more irregularly shaped flocs, which did great harm to membrane filtration. The sludge flocs with a small quantity of filamentous bacteria had a positive effect on membrane permeation. It is important to control filamentous bacteria concentration in the operation of MBRs.

This paper examines the influence of activated sludge properties such as the mixed liquid of suspended solids (MLSS) concentration, sludge particle size distribution (PSD), extracellular polymeric substances (EPS), soluble microbial products (SMP), suspended solids in supernatant (SSs), dynamic viscosity (µ), relative hydrophobicity (RH), and zeta potential on membrane fouling. ctivated sludge samples from different full-scale and lab-scale membrane bioreactor processes were used to study their impacts on membrane fouling. The influence of activated sludge properties on membrane permeation was identified with statistical methods. The results showed that MLSS concentration had an exponential relationship with membrane fouling resistance. The sludge particle size (rp=−0.730) was correlated inversely to the membrane fouling resistance significantly. The total EPS (rp=0.898) and protein (rp=0.810) had strong positive effect on membrane fouling resistance, but carbohydrate (rp=0.626) had a moderate correlation with membrane fouling resistance due to its low amounts. SMP (rp=0.757), SSs (rp=0.810), dynamic viscosity (rp=0.691), RH (rp=0.837), and zeta potential (rp=−0.881) also had significant influence on membrane permeability. However, protein (rp=0.936), SMP (rp=0.725), SSs (rp=0.783), dynamic viscosity (rp=0.633), RH (rp=0.877), and zeta potential (rp=−0.953) mainly resulted from the change of EPS concentration. These results confirm that MLSS concentration, PSD and EPS were the predominant factors affecting membrane fouling during membrane filtration of sludge suspension. The membrane fouling resistance can be predicted using a simple model based on MLSS concentration, PSD and EPS.

The membrane bioreactor (MBR) is an important process widely used in wastewater treatment. However, membrane flux declines rapidly due to membrane fouling, which limits the application of MBR. In order to alleviate membrane fouling, a precoated dynamic membrane (PDM) was studied systematically. The membrane module consisted of of 56-µm terylene filter cloth as the support membrane and powder-activated carbon (PAC) as the precoating reagent. The precoated dynamic membrane bioreactor (PDMBR) was used in municipal wastewater treatment practice. Meanwhile, from the viewpoint of retention capacity, flux recovery and alleviating membrane fouling, the suitable thickness of the PAC dynamic membrane was also investigated. The experimental results showed that the formation of PDM from PAC on a support membrane belonged to the cake filtering model, and the relationship of PDM resistance (Ra) and its thickness (D) was in accord with log-function; the suitable thickness was controlled around 0.3 mm. It was found that while the flux of PDM was kept at a high value, the operating pressure of PDM rose to 42 kPa after 43 days of stable operation of the PDMBR, and the removal efficiency of effluent COD and NH4+-N were as good as traditional hollow membrane bioreactors. Furthermore, the flux of the fouled membrane could be totally recovered just after being cleaned by brushing, and it did not consume any chemical reagents. Moreover, it was also found that the PDM could prevent biomass contaminations diffusing from the surface inwards by scanning electron microscopy (SEM).

采用孔径56μm的工业滤布制作膜组件，以PAC作为预涂剂，组成预涂动态膜-生物反应器。对比预涂膜、未预涂膜和014μm中空纤维膜的污染物去除效果和膜污染状况。试验结果发现，预涂动态膜2生物反应器不仅污染物质去除效果更好，而且预涂膜可以防止污染物质与微生物向膜材料表面和内部扩散，从而减轻膜污染，运行1128h后，操作压力仅上升至6kPa，并且只需刷洗，膜通量就可以恢复，无须消耗化学试剂。

对序批式运行方式强化膜生物反应器脱氮除磷效果进行了研究。在试验过程中逐渐降低进水CODPTN值，提高总氮负荷，比较序批式膜生物反应器和传统膜生物反应器的脱氮除磷性能与膜污染状况。试验结果表明，进水CODPTN降至318～813，总氮负荷提高至0122kg·m-3·d-1时，传统膜生物反应器无法脱氮，而序批式膜生物反应器通过改变周期、提高交换比等方式，TN和氨氮去除率分别保持在6716%和9311%.序批式的运行方式还可以减轻膜污染.