滤层厚度对慢滤池深度处理污水的性能影响

将慢滤池用于污水二级出水的深度处理，并利用小试装置研究了滤层厚度对慢滤池性能的影响。选取浊度、COD和色度三个指标，在滤层不同深度处多次取样，分析各指标沿滤层厚度的变化。结果表明，采用粒径为0．4～0．6mm，滤层厚度为800mm的石英砂做滤床时，慢滤池对二级出水具有较好的净化效果：当进水浊度、COD和色度分别为1.3～6．9NTU、30．4～70．0mg·L^-1和20．6°～57．6°时，平均去除率分别达到86．5％、45．0％和46．3％。从试验结果可以看出，慢滤池类似一个微缩的污水二级处理系统，滤层表面的粘性滤膜起到类似初沉池的作用，可以对各指标实现较好的去除，58．6％的浊度、52．7％的COD和45．7％的色度是在滤层上部去除的；慢滤池中部起到类似曝气池的作用，下部起到类似二沉池的作用，对水质指标也能实现一定的去除。

Experimental study of the filter bed depth on performances of a slow sand filter used for wastewater advanced treatment

A lab-scale slow sand filter was used for advanced treatment of secondary effluent of domestic wastewater. Performances of the slow sand filter along the filter bed were deliberately studied. Results showed that the average removal rates of turbidity, COD and color were 80.0%, 46.3% and 35.1% during a period with the influent turbidity, COD and color were 1.3～6.9 NTU, 30.4～70.0 mg·L~(-1) and 20.6～57.6 degree respectively. The test shows that slow sand filter is like a miniature wastewater secondary treatment systems. The schmutzdecke layer of the upper filter bed is similar with the Primary sedimentation tank, and contributes 58.6%, 52.7% and 45.7% of the total removal amount of turbidity, COD and color; the central and lower regions of filter can respectively play the role of Aeration tank and secondary settling tank, they also achieve a certain purifying effect. All data showed that 800mm depth of sands with grain sizes of 0.4～0.6 mm are suitable for a slow sand filter used for secondary effluent of wastewater polishing.