It includes physical method, biological method and chemical method based on the function.

① Physical Method: Separate the insoluble matters in sewage by utilizing the physical interaction and will not change the chemical nature during the treatment. The common methods include gravitational separation, centrifugal separation, reverse osmosis and air flotation. To process the buildings with the physical method is simple and economic. So, it is used in the situation with high capacity of water from village and town, strong self-cleaning capacity and lower requirements for sewage treatment degree.
②Biological Method: Use the microorganic metabolism function to decompose and oxidize the organic matter with the dissolved or colloidal state in the sewage into the stable inorganic matter so as to make the sewage purified. The common methods include the activated sludge process and biofilm process. The treatment degree with biological method is higher than that with the physical method.
③ Chemical Method: It is a kind of method to process or recycle the dissolved or colloidal matters in the sewage by using the chemical reaction. It is often applied in the industrial wastewater. The common methods include the coagulation method, neutralization method, oxidation reduction method and ion exchange method. The treatment results with the chemical method are good with high costs. It is used for the further treatment of effluent after biological treatment so as to improve the effluent quality.

The sewage energy saving treatment system can be divided to primary treatment, secondary treatment and tertiary treatment according to the treatment degree.

The primary treatment is mainly to remove the solid matters with suspended state in the sewage. The physical method is often used. The removal rate of wastewater BOD after the primary treatment is only 20%. So, it is not suitable to be discharged. It is necessary for the secondary treatment. The main task of secondary treatment is to sharply remove the organic matters with the colloidal and dissolved state in the sewage. The removal rate of BOD is 80%--90%. The sewage after secondary treatment can meet the discharging standard. The activated sludge process and biofilm process are commonly used. The tertiary treatment is to further remove some special contaminants including fluoride, phosphorus. The deep treatment needs to use the chemical method.

Sewage technical process selection requirement: strengthen the reconstruction of treatment results for the existing primary treatment process. The reconstruction should base on the actual situation and existing treatment facilities. To transform the structure or running way of septic tank and contact tank widely applied in the existing hospitals. If necessary, to add the part of facilities and try to improve the treatment results so as to reach the discharging standard of sewage treatment of hospital. 

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