With enterprises increase, population increase, industrial waste and sewage increase, quality of river water deteriorate,groundwater are polluted seriously and incidence of cancer increases.Due to BOD, COD and oil in discharged water far exceeds national standards and river pollution receiving capacity, pollution is increased.The most serious impact of water pollution is damage ecological environment and ecological system of the whole urban. Once the ecological environment is broken, it is very slow and difficult to recover.The situation does not permit of any delay.Wastewater treatment can improve the quality of life for residents, beautify the urban environment,and be propitious to urban development, also make a good foundation for investment and the construction of town.
Sewage flows into sewage processing factory after pipeline collection, then flows through rough grid that hinder large solid garbage, and then flows to lift pump, which lift sewage to fine grid that further remove the small suspended matter and small fiber and reduce Bio-processing load. Then flow into Grit Chamber with Rotational Flow, using hydraulic Eddy makes sand grain and sewage separate, to protect subsequent device from wear, effectively reduce maintenance. after above pretreatment , sewage flows into hydrolysis acidification pool to homogenize the quality and quantity of the water, and convert organic matter which is difficult to biodegrad into small organic matter which is easy to Aerobic Bacteria Biochemical Treatment ,if necessary, can be used as treatment pool.After sewage is treated preliminarily in the Hydrolysis acidification pool,it flows into CASS reaction pool, which have several stages: aeration , precipitation, decant water and idle (details see CASS reaction pool process figure) ,after that the pollutants are effectively remove, then entered into Ultraviolet disinfection of pool, with UV for disinfection, after that water directly discharge outside.the sludge produced in the process of sewage treatment are dehydrated by dehydration device, and then can be buried or make brick.
（1）The process flow is simple, layout is compact, operation is flexible, it can achieve removal of nitrogen and phosphorus without adding a large number of investment.
（2）The investment is relative low. concrete dosage and construction investment is low, because it is not necessary to set early sinking pool and the secondary sinking pool. it is not necessary to set the huge scraping mud bridge, lots of mixing device and huge Sludge reflux and internal reflux pump in the system, so the investment system machinery/device is low.
（3）The operational cost is low. Because sludge reflux ratio is low and mixing is without energy consumption, it saves a lot of energy. The operation of the process system is fully automated, and minimize the cost of maintenance and personnel.
（4）Adaptability. That adjust the cycle time and the timing of the stage can be adapted to the actual water load.
（5）Occupay small area. generally use the modular construction of the rectangular pool structure, whose layout is very compact and system expansion is easy.
（6）It can minimize the impact to the surrounding environment. The noise can be controlled in less than 60 decibels .