近年来，膜生物反应器中膜污染的研究日益活跃，取得了较大的成果，并面临着突破性进展。分形理论使膜污染凝胶层微观结构的研究成为可能，为膜污染的研究提供了新的思路。本文对分形理论在过滤滤饼结构中的应用进行了较为全面的综述，并指出了其在膜污染研究中的应用前景。

This study is to evaluate the utility of a strategy of stepwise increased selection pressure for cultivating aerobic granules. Three sequencing batch reactors (SBR; R1-R3) were used. Substrate ammonium-nitrogen (NH4+-N) concentration was a microbial selection pressure for selecting nitrifying bacteria. It was stepwise increased from 50 to 200mg l−1 in R2 and fixed at 50mg l−1 in R1 and 200mg l−1 in R3. Results showed that aerobic granules failed to be developed in R3 due to free ammonia (FA) inhibition, while they formed quickly in both R1 and R2. Filamentous dominated granules in R1 exhibited poor performance and started to disintegrate from day 131. Stepwise increased selection pressure in R2 selected slow-growing nitrifying bacteria gradually, and this suppressed filamentous growth and improved the stability of aerobic granules. During the 283 days operation, R2 produced aerobic granules with incrementally higher biomass concentration, better settleability, and larger granule size. Larger granules further favored denitrification and the optimal granule size is suggested to be controlled within 2-3mm. This study demonstrates the successful application of the strategy of stepwise increased selection pressure for avoiding the failure of aerobic granulation and improving the stability and performance of aerobic granules.

采用平行试验的方式对比序批式膜生物反应器与传统膜生物反应器在不同进水碳氮比条件下对污染物质的去除效果。试验结果表明，序批式膜生物反应器强化了传统膜生物反应器的脱氮除磷性能。进水碳氮比在（7.8～32.2）:1范围内，序批式膜生物反应器TP平均去除率为93.9%，TN平均去除率由传统膜生物反应器的31.8%提高至87.4%，且保持稳定，无需外加碳源.序批式膜生物反应器混合液EPS含量高于传统膜生物反应器。

Cake layer formed on membrane surface presents a major challenge to membrane permeation, and it can be considered as a porous media. Determination of the cake layer permeability is critical for an accurate analysis and design of membrane filtration. A permeation model, based on fractal theory and Darcy's law, for evaluating cake layer permeability in microfiltration of activated sludge wastewater was developed. The cake layer permeability was derived and found to be a function of the pore-area fractal dimension and microstructural parameters. The validity of the model was studied systematically in this paper. The permeation model was applied to study the effect of mixed liquid suspended solids (MLSS) concentration, particle size distribution (PSD) and extracelluler polymeric substance (EPS) on cake layer permeability in a submerged membrane bioreactor. Results showed that the permeation model was a useful tool to study the micromechanism of membrane fouling. There was a close correlation between MLSS concentration and cake layer permeability. There were a slight and a distinct decrease of the cake layer permeation as MLSS increased less and larger than 10,000mg/L, respectively. PSD and EPS are two significant factors affecting cake layer permeability in membrane bioreactor. Effect of activated sludge on cake layer permeability was mainly caused by EPS and small particles attached on membrane surface.

An operation of a membrane bioreactor in sequencing batch mode named a sequencing batch membrane bioreactor (SBMBR) was investigated for enhancing nitrogen and phosphorus removal. Its performance was compared with a conventional membrane bioreactor (CMBR) at various influent COD/TN ratios of 3.4-28.2. The operational parameters were optimized to increase the treatment efficiency. COD removal averaged at 94.9 and 97.7%, respectively, for SBMBR and CMBR during the 8 months experimental period. The SBMBR system demonstrated good performance on nitrogen and phosphorus removal at different COD/TN ratios. When COD/TN was 6.3 and the total nitrogen (TN) load was 0.22kg/(m3 days), the TN and ammonium nitrogen removals of the SBMBR were maintained over 65 and 90%, respectively. Total phosphorus (TP) removal of the SBMBR was approximately 90% during most of the experimental time. In comparison, the CMBR did not perform so well. Its effluent TN concentration was close to that in the influent at COD/TN=6.3 and TP removal was not stable. The specific nitrification rate test showed that pH value affected the activity of nitrifiers but no irreversible harm was induced. Furthermore, the sequencing batch mode operation of MBR retarded membrane fouling according to the monitoring of trans-membrane pressure (TMP).