TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The city sewage collecting system utilizes the existing sewage processing factory of the system. The conveying system utilizes a large caliber pipeline and a multi-stage pump station. The filter sieve dividing device comprises a trapezoidal table, a coarse filter, a fine filter basket and a sewage collecting slot. The bottom periphery of the trapezoidal table is provided with the sewage collecting slot. The sewage collecting slot is set at the bottom end of a water outlet. The upper part of the trapezoidal table is provided with the fine filter basket. The fine filter basket is set in a thick filter hanging basket. The sewage collecting slot is provided with several filtering net bags. The inclined plane of the trapezoidal table is provided with a filter frame. The sand filter purifying pool comprises a water tank inlet, a water tank outlet, the water tank, a filter plate, a filter material, filter sand and a supporting net. A large slot body is set adjacent to the water tank inlet and water tank outlet. There is an isolation zone between the water tank inlet and water tank outlet. The water tank inlet and water tank outlet is set at the bottom of the filter plate to form a triangle and is parallel to a sewage channel. The length direction of the sewage channel is similar to the length direction of the tank. The sewage channel and the tank are connected to the water inlet tank and water outlet tank. The filter plates are laid on the supporting net. The filter material is filled between the filter plate and the supporting net. The supporting net is spread on a layer of filter sand. The sand filtering purifying pool is set next to a sludge fermentation tank. The sand filtering purifying pool is set at the bottom of the sludge discharging channel. The sludge discharging channel is connected to the sludge fermentation tank. The sludge discharging channel of the sludge fermentation tank is provided with a gate.