Biological sewage treatment: the use of microbial metabolism sewage treatment equipment, the sewage was dissolved or colloidal organic matter oxidative decomposition of stable inorganic material, the sewage purification. Conventional activated sludge and biofilm. Biological treatment level is higher than the physical method. Wetland suitable for handling pure sewage or rainwater and sewage water, sewage treatment equipment larger area where the good, should adopt two series; planar shape biofilter should adopt a circular or rectangular. Packing should be hard and, corrosion resistance, high strength, large specific surface area, porosity, should adopt the gravel, gravel, slag, coke and other inorganic media; geographical environment suitable and technical conditions permit, the village sewage may be considered wasteland, Waste land and ponds, depressions and other stabilization pond treatment system. Stabilization ponds used for secondary treatment system, deal with the scale of not more than 5000m3 / d.