Selection of hospital sewage treatment process flow:

（1） Select the process based on the scale, nature, and discharge direction of the hospital's treated wastewater. According to hospital classification, it is divided into infectious disease hospitals and comprehensive hospitals. The discharge direction of hospital sewage after treatment is divided into two categories: discharge into natural water bodies and discharge into urban sewage treatment plants through municipal sewers.

The processes used in hospital sewage treatment must ensure that the treated water meets the standards. The three main processes used are: primary treatment to enhance treatment efficiency, secondary treatment, and simple biochemical treatment. The principle of process selection is:

1. Infectious disease hospitals must adopt secondary treatment and undergo pre disinfection treatment.

2. Hospitals at or above the county level that discharge effluent into natural water bodies must adopt secondary treatment.

3. Comprehensive hospitals that discharge treated effluent into urban sewers (with downstream secondary sewage treatment plants) recommend using secondary treatment. For those using primary treatment processes, it is necessary to strengthen the treatment effect.

4. For small comprehensive hospitals in economically underdeveloped areas, simple biochemical treatment can be used as a transitional treatment measure when conditions are not available, and then gradually achieve secondary treatment or enhance the treatment effect of primary treatment.

（2） Considering the above principles, the application of different treatment processes is compared in the hospital sewage treatment process designed in this plan

With the continuous development of sewage treatment technology, the commonly used processes developed in recent years both domestically and internationally include:

1. Primary treatment process to enhance treatment effectiveness

For comprehensive hospitals that treat wastewater and ultimately enter secondary urban sewage treatment plants, their treatment efficiency should be strengthened, the removal rate of SS should be improved, and the amount of disinfectant used should be reduced. There are two ways to enhance the effectiveness of primary treatment: modifying the existing primary treatment process to enhance removal efficiency and adopting primary enhanced treatment technology.

1) Process flow

For sewage treatment in general hospitals (without infectious disease wards), the process of "pre-treatment → primary enhanced treatment → disinfection" can be adopted. By using coagulation precipitation (filtration) to remove particles carrying viruses and pathogens, the disinfection effect is improved and the dosage of disinfectants is reduced, thereby avoiding adverse effects on the environment caused by excessive dosage of disinfectants.

The hospital sewage enters the regulating tank through a septic tank, and an automatic grille is installed in the front of the regulating tank. There is a lifting water pump inside the regulating tank. After being lifted, the sewage enters the coagulation and sedimentation tank for coagulation and sedimentation. The effluent from the sedimentation tank enters the contact tank for disinfection, and the effluent from the contact tank meets the discharge standards.

The waste generated in the sewage treatment plant, such as sludge and grid residue from the regulating tank, coagulation sedimentation tank, and contact tank, is centrally disinfected and transported out. Disinfection can be carried out using methods such as pasteurization or adding lime.

2) Process characteristics

Strengthening the first level of treatment can improve the treatment effect, remove particles carrying viruses and pathogens, improve the subsequent deepening disinfection effect, and reduce the dosage of disinfectants. Reforming the existing primary treatment process can fully utilize existing facilities and reduce investment costs.

3) Applicable scope

The primary enhanced treatment for enhancing treatment efficiency is suitable for comprehensive hospitals that treat effluent and ultimately enter secondary treatment urban sewage treatment plants.

2.Secondary treatment process

1) Process Description

The secondary treatment process flow is "regulating tank → biological oxidation → contact disinfection". Hospital sewage enters the regulating tank through septic tanks. Automatic grille is installed at the front of the regulating pool. The regulating pool is equipped with a lifting water pump. After the sewage is lifted, it enters the aerobic pool for biological treatment. The effluent from the aerobic pool enters the contact pool for disinfection, and the effluent meets the discharge standards.

The waste generated in the sewage treatment plant, such as sludge and slag from regulating tanks, biochemical treatment tanks, and contact tanks, is centrally disinfected and transported for incineration. Disinfection can be carried out using methods such as pasteurization or adding lime.

Sewage and feces from infectious disease hospitals are collected separately at a lower cost. Domestic sewage directly enters the pre disinfection tank for disinfection treatment before entering the regulating tank. The patient's feces should be disinfected independently before entering the septic tank or being treated separately through the sewer (as shown by the dotted line). Each structure must operate in a closed environment, with ventilation through a unified ventilation system. The exhaust gas is discharged after disinfection, and ultraviolet disinfection system can be used for disinfection.

2) Process characteristics

The aerobic biochemical treatment unit removes organic pollutants such as CODCR and BOD5. The aerobic biochemical treatment can choose from contact oxidation, activated sludge, and high-efficiency aerobic treatment processes, such as membrane bioreactors and aerated biofilters. Adopting an efficient aerobic treatment process with filtering function can reduce the concentration of suspended solids, which is beneficial for subsequent disinfection.

3) Applicable scope

Suitable for sewage treatment in infectious disease hospitals (including comprehensive hospitals with infectious wards) and comprehensive hospitals discharged into natural water bodies.

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