Control of Fouling Substances in Membrane Bioreactors with Intermittent Aeration

通过改变有机负荷和间歇曝气周期对间歇曝气浸没式膜分离活性污泥法的性能进行了小试研究。曝气池采用矩形聚氯乙烯曝气池，在曝气池中浸入孔径为0.2μm的聚烯烃制成的平板型微滤膜。反应器的有机负荷分别为0.3和0.8g-TOC/L/天。在每种条件下，饲料中的C/N比都设定在5.0左右。在不同的有机负荷条件下，曝气周期从10min-10min(曝气-停止)到120min-120min。膜通量设定为0.25m/d。在0.8g-TOC/L/天的条件下，膜污染发展迅速。然而，当有机负荷为0.3g-TOC/L/天时，细菌代谢物质的降解速度比产量快，从而降低了混合液的粘度。对0.8g-TOC/L/d负荷和0.3g-TOC/L/d负荷，脱氮率分别为60%~80%和50%~65%。曝气周期为40~60min时，脱氮效果最好。曝气周期过短不会产生足够长的反硝化缺氧期，而过长的曝气周期会导致硝酸盐耗尽后不必要的厌氧期。间歇曝气对降低混合液粘度也是有效的。

The performance of the submerged membrane separation activated sludge process with intermittent aeration was investigated in a laboratory scale experiment changing organic loading rate and intermittent aeration cycle. A rectangular PVC tank was used as an aeration tank, in which a flat-sheet type Micro-Filtration membrane made of poly-olefin with the pore size of 0.2μm was submerged. Organic loading rate to the reactor was set at 0.3 and 0.8 g-TOC/L/day. C/N ration in the feed was set at around 5.0 for every condition. Aeration cycle was changed from 10min-10min (aeration - stop) to 120min-120min in different organic loading conditions. Flux through the membrane was set at 0.25m/day. Membrane fouling proceeded rapidly in 0.8 g-TOC/L/day conditions. However, when organic loading rate was 0.3 g-TOC/L/day, bacterial metabolic substances were degraded rapidly compared to the production thereby decreasing viscosity in mixed liquor. Nitrogen removal rate was between 60% and 80% for 0.8 g-TOC/L/day loading, and between 50% and 65% for 0.3 g-TOC/L/day loading. And the nitrogen removal was highest in 40min to 60min aeration cycle conditions. Too short aeration cycle did not result in sufficiently long anoxic periods for denitrification while too long cycle resulted in unnecessary anaerobic periods after depletion of nitrate. Intermittent aeration was effective also for decreasing viscosity in mixed liquor.