Sewage treatment

① Environmental protection requirements for sewage treatment degree;

(2) The amount and quality of sewage;

(3) Investment capacity. Sewage treatment technology is to use various methods to separate the pollutants contained in the sewage, or convert the pollutants into harmless substances, so that the sewage can be purified.

Treatment method

According to the function;

Sewage treatment can be divided into physical method, biological method and chemical method according to its role.

Physical method: The main use of physical action to separate insoluble substances in sewage, in the treatment process does not change the chemical properties. Commonly used are gravity separation, centrifugal separation, reverse osmosis, air flotation and so on. The physical method is simple and economical to treat structures, which is used for the situation of large water capacity, strong self-purification ability and low requirement of sewage treatment degree in villages and towns.

② Biological method: Using the metabolic function of microorganisms, the organic matter in the sewage is dissolved or colloidal state is decomposed and oxidized into stable inorganic substances, so that the sewage is purified. Activated sludge method and biofilm method are commonly used. The degree of treatment by biological method is higher than that by physical method.

Chemical method: It is a method of using chemical reaction to treat or recycle dissolved substances or colloidal substances of sewage, which is mostly used in industrial wastewater. Commonly used are coagulation method, neutralization method, REDOX method, ion exchange method, etc. The chemical treatment method has good treatment effect and high cost, and is mostly used as the effluent after biochemical treatment for further treatment to improve the effluent quality.

According to the degree of treatment

Sewage treatment can be divided into primary treatment, secondary treatment and tertiary treatment according to the degree of treatment.

Primary treatment is mainly to remove solid substances in the suspended state of sewage, and physical methods are commonly used. The removal rate of BOD of wastewater after primary treatment is only 20%, which is still not suitable for discharge, and secondary treatment is also required. The main task of secondary treatment is to greatly remove colloidal and dissolved organic matter in sewage, and the BOD removal rate is 80% to 90%. Generally, after secondary treatment, the sewage can meet the discharge standard, and the activated sludge method and biofilm treatment are commonly used. The purpose of tertiary treatment is to further remove a special pollutant, such as fluorine removal, phosphorus removal, etc., which is an advanced treatment and commonly used chemical method.

1. The transformation of the existing primary treatment process to strengthen the treatment effect should be based on the actual situation, make full use of the existing treatment facilities, and transform the structure or operation mode of the septic tank and contact tank that are widely used in the existing hospital, and add some facilities if necessary to improve the treatment effect as much as possible. To meet the discharge standards of hospital sewage treatment.

Primary enhanced treatment

1. Process description

For sewage treatment in general hospitals (non-infectious wards), the process of "pretreatment → primary intensive treatment → disinfection" can be adopted. Through coagulation precipitation (filtration) to remove the particles carrying viruses and germs, improve the disinfection effect and reduce the amount of disinfectants, so as to avoid the adverse impact of excessive disinfectants on the environment. The hospital sewage enters the regulating tank through the septic tank. The regulating tank is equipped with an automatic grille in front of the regulating tank and a lifting pump in the regulating tank. After the sewage is lifted, it enters the coagulation sedimentation tank for coagulation and precipitation. The effluent from the sedimentation tank enters the contact tank for disinfection, and the effluent from the contact tank is discharged according to the standard.

The waste generated in the sewage treatment station, such as sludge and grid slag in the regulating tank, coagulation settling tank, contact tank, etc., is centrally disinfected and transported. Disinfection can be done by pasteurizing steam or adding lime.

2. Process characteristics

The first-level intensive treatment can improve the treatment effect, remove the particles carrying viruses and germs, improve the effect of further disinfection and reduce the amount of disinfectant. The transformation of the existing primary treatment process can make full use of the existing facilities and reduce the investment cost.

3. Scope of application

The primary intensive treatment is suitable for general hospitals where the treated effluent ends up in the secondary municipal sewage treatment plant.

Secondary treatment technology

1. Process description

The secondary treatment process is "regulation tank → biological oxidation → contact disinfection". Hospital sewage enters the regulating tank through the septic tank. An automatic grille is provided at the front of the regulating pool. The lifting pump is set in the regulating tank. After the sewage is lifted, it enters the aerobic tank for biological treatment. The effluent from the aerobic tank enters the contact tank for disinfection.