Unit 18 biological filter

1. Unit 18 biological filter 生物膜法

2. Sludge worms, filter-fly larvae, rotifers, and other higher animals frequently find the environment suitable for growth. • 污泥虫，滤池蝇幼虫，轮虫及其它一些高等动物经常生长在（生物滤池）这样适合的环境中。

3. As the waste water flows over the microbial film, the soluble organics are rapidly metabolized and the colloidal organics absorbed onto the surface. • 当废水流过生物膜上，可溶性有机物很快被代谢，胶体状态的有机物则被吸附到生物膜表面。

4. Microorganisms near the surface of the bed ,where food concentration is high , are in a rapid growth phase, while the lower zone of a bed is in a state of starvation. • 靠近底物浓度高的滤床表面的微生物处于快速生长状态，而滤床（生物膜）内较深的区域微生物处于饥饿状态。

5. Plugging of the air passages with excess microbial growth , as a result of organic overload, can create anaerobiosis and foul odors. • 微生物过量生长而堵塞空气通道，结果有机超负荷，从而造成（微生物）厌氧生活及产生恶臭气体。

6. In recent years several forms of manufactured plastic media have been marketed, their main advantages being light weight, chemical resistance and high specific surface (m2/m3)with a large percentage of free space. • 近些年有些人造的塑料介质打入市场，它们的主要优点是重量轻，有化学耐性及高的比表面积，因其具有大的空隙率。

7. Nevertheless, when treating high-strength or cold wastewater ,single-stage filters cannot provide sufficient organic removal to meet the effluent standard of 30mg/L of BOD,and in the case of two-stage systems the first unit under high loading may have problems of bed plugging and emission of foul odors. • 但是，当处理高浓度或低温废水时，单级滤池不能提供足够的有机物去除率来满足出水BOD30mg/L的要求，且二级滤池系统第一个单元在高负荷的情况下可能出现滤床堵塞和释放恶臭气体的问题。

8. A uniform medium also allows even loading distribution, and lightweight packing permits the construction of deeper beds with the ability to handle high-strength wastes. 整齐一致的介质使得负荷分布均匀，而且重量轻的填料使滤池可以建造得更深，从而能够处理高浓度废水。