Synthetic wastewater was treated with a submerged membrane bioreactor to investigate the organic removal performance, as well as the behaviour of soluble microbial products during long-term operation. Satisfactory chemical oxygen demand (COD), total organic carbon (TOC) and biological oxygen demand (BOD) removal efficiencies were achieved, averaging over 90, 94 and 95%, respectively. The accumulation of TOC in the supernatant of the bioreactor and its degradation after 5 months of operation was observed. Among this accumulation, macromolecules with a molecular weight (MW)\100000 accounted for 34%. A decrease in the supernatant TOC corresponded to a shift from large to small molecules. The organic substances with a MW\100000 decreased from 34 to 16%, whereas those with a MWB30000 increased from 33 up to 52%. The accumulation proved to be inhibitory towards the metabolic activity of the activated sludge, as well as contributing to the poor membrane permeability of the mixed liquor.

通过静态吸附试验表明，粉末活性炭（PAC）为天然腐殖质类物质饱和后仍可吸附二氯酚（DCP），并在连续运行试验中进一步验证了PAC-MBR抗DCP冲击负荷的能力强于投加普通填料的MBR。通过测定进、出水有机物的表观分子质量分布，发现PAC-MBR 能有效去除1～4K（1K=1000u）的有机污染物，对4K～0.45μm有机物的去除与PAC的饱和程度有关，去除率随运行时间延长而逐渐降低。PAC-MBR和普通填料-MBR均能有效去除可生物降解有机物，前者对可吸附有机物的去除率受PAC饱和程度的影响较大。采用磷脂法可测定PAC上附着的活性微生物量，连续运行中PAC-MBR内的微生物量为0.6×10 8个活细胞PmL，与普通填料- MBR相当。耗氧速率测定结果表明，PAC-MBR内的微生物活性略高于投加普通填料的MBR。

采用普通微网材料加工的过滤组件与生物反应器一起构成动态膜-生物反应器，研究了微网上所形成的生物动态膜的过滤性能。生物动态膜所具有的较强截留能力主要是由附着的凝胶层产生。动态膜对相对分子质量<3×10 3至>1×10 5的各个级别的溶解性有机物都有30%～60%的截留率，但过滤的精度并不很高，不能完全截留相对分子质量大于1×10 5的溶解性有机物。已经覆盖有凝胶层的膜片与未使用过的新膜片的清水过滤阻力几乎相等，约为119×10 9m-1，由滤饼产生的过滤阻力占运行中动态膜片总过滤阻力的绝大部分，新膜片在清水通过时有明显的初始阻力，而有凝胶层覆盖时的膜片几乎没有初始过滤阻力。

In the present study, an orthogonal array design was adopted to investigate effects of operational parameters including aeration intensity, membrane flux, suction time and non-suction time on sludge accumulation on membrane surfaces respectively at a high SS concentration of 10g 1-l and a low SS concentration of 1g I-1 in a submerged membrane bioreactor. Average transmembmne pressure (TMP) increase rate over the operation time was used to evaluate sludge accumulation. Among the four factors, membrane flux was found to influence Th4P the most obviously. The effect of aeration intensity became significant only at a high SS concentration of 10g I-1TMP increased with suction time and decreased with non-suction time. There was a critical membrane flu over which sludge particles were deposited, and accordingly, ThW increased sharply. Two zones, predicting whether sludge particles are deposited or not, could be comprehensively determined by the critical flux, correspondent aeration intensity and SS concentration. For long-term stable operation, it is suggested that a membrane bioreactor be operated in the zone with prediction of no obvious sludge deposit on membrane surfaces.

To clarify the effect of sludge retention time (SRT) on performance and microbial behaviour in a submerged membrane bioreactor for the treatment of domestic wastewater, four runs of a laboratory scale reactor with hydraulic retention time of 5h and SRTs of 5, 10, 20 and 40 days, respectively, were conducted. The membrane bioreactor process was capable of achieving over 90% removals both for chemical oxygen demand and ammonia nitrogen, on average, almost independent of SRT. With prolonged SRT, concentrations of suspended solids and volatile suspended solids in the bioreactor increased accordingly, whereas sludge growth kinetic parameters, sludge yield and endogenous decay coefficients, declined slightly and exponentially, respectively. The mean sludge particle sizes at different SRTs were in the range 14.82-48.24m, providing a favourable environment for enhancement of mass transport. Characterized by an oxygen consumption rate, sludge specific activities both for organic decomposition and nitrification of ammonia nitrogen varied with SRT. However, volumetric oxygen consumption rates of the membrane bioreactor, representing the whole ability of the process for decomposing pollutants, were enhanced as SRT increased.