Hospital sewage treatment process

1 Process selection principles

According to the scale and nature of the hospital and the destination of the sewage treatment, the process selection is carried out. According to hospital classification, it is divided into infectious disease hospitals and general hospitals. The discharge destination of hospital sewage after treatment is divided into two types: discharge into natural water and discharge into urban sewage treatment plants through municipal sewers.

The process used in hospital sewage treatment must ensure that the treated effluent meets the standards. The three main processes used are: primary treatment to enhance the treatment effect, secondary treatment and simple biochemical treatment.

The principle of process selection is:

1.1 Infectious disease hospitals must adopt secondary treatment and require pre-disinfection treatment.

1.2 County and above hospitals that treat effluent into natural water bodies must adopt secondary treatment.

1.3 The general hospital that treats the effluent discharged into the city sewer (the secondary sewage treatment plant is downstream) recommends the use of secondary treatment. The treatment effect must be strengthened for those who adopt the primary treatment process.

1.4 For small general hospitals in economically underdeveloped areas, when conditions are not available, simple biochemical treatment can be used as a transitional treatment measure, and then the second-stage treatment or the first-stage treatment to strengthen the treatment effect is gradually realized.

2 Primary treatment process to enhance treatment effect

For comprehensive hospitals that treat the effluent and eventually enter the secondary treatment urban sewage treatment plant, the treatment effect should be strengthened, the SS removal rate should be increased, and the amount of disinfectant should be reduced. Strengthening the primary treatment effect should be achieved in two ways: transforming the existing primary treatment process to enhance the removal effect and using primary enhancement treatment technology.

2.1 Process flow

1. Renovate the existing primary treatment process to enhance the treatment effect
According to the actual situation, the transformation should make full use of the existing treatment facilities, transform the septic tanks and contact tanks used in existing hospitals in terms of structure or operation mode, and add some facilities if necessary to improve the treatment effect as much as possible In order to meet the discharge standards of hospital sewage treatment.
2. First-level strengthening treatment
For the treatment of sewage in general hospitals (without infectious wards), the process of “pretreatment → first-level intensive treatment → disinfection” can be used. Removal of particles carrying viruses and germs through coagulation sedimentation (filtration) improves the disinfection effect and reduces the amount of disinfectant, thereby avoiding the adverse effects of excessive disinfectant on the environment.
Hospital sewage enters the adjustment tank through the septic tank. An automatic grill is set in the front of the adjustment tank, and a lifting pump is installed in the adjustment tank. After the sewage is lifted, it enters the coagulation sedimentation tank for coagulation and sedimentation. The effluent from the sedimentation tank enters the contact tank for disinfection.
Regulation tanks, coagulation sedimentation tanks, contact tank sludge and grid slag and other garbage generated in sewage treatment stations are concentrated for disinfection and transported out. Disinfection can be done by pasteurization or lime addition.

2.2 Process characteristics

Enhance the treatment effect. The first-level enhancement treatment can improve the treatment effect, remove the particles carrying viruses and bacteria, improve the effect of subsequent deepening disinfection and reduce the amount of disinfectant. Among them, the transformation of the existing primary treatment process can make full use of existing facilities and reduce investment costs.

2.3 Scope of application

Intensified treatment effect The first-level enhanced treatment is suitable for the treatment of effluent and finally enters the general hospital of the second-level urban sewage treatment plant.

3 Secondary treatment process

3.1 Process description

The process flow of secondary treatment is “regulating tank → biological oxidation → contact disinfection”. Hospital sewage enters the regulating tank through the septic tank. Adjust the automatic grille in the front of the tank. A lifting pump is installed in the regulating tank. After the sewage is lifted, it enters the aerobic tank for biological treatment. The aerobic tank effluent enters the contact tank for disinfection, and the effluent reaches the standard for discharge.

Regulation tanks, biochemical treatment tanks, contact tank sludge and grid slag and other waste generated in sewage treatment stations are concentrated for disinfection and incineration. Disinfection can be done by pasteurization or lime addition.

Infectious disease hospital sewage and feces are collected separately cheaply. The domestic sewage directly enters the pre-disinfection tank for disinfection treatment and then enters the adjustment tank. The patient’s feces should be independently disinfected, and then enter the septic tank through the sewer or be treated separately (as shown by the dotted line). Each structure must be operated in a closed environment, and the ventilation should be performed through a unified ventilation system. The exhaust gas is discharged after disinfection. The ultraviolet disinfection system can be used for disinfection.

3.2 Process characteristics

Aerobic biochemical treatment unit removes CODcr, BOD5 and other organic pollutants. Aerobic biochemical treatment can choose contact oxidation, activated sludge and high-efficiency aerobic treatment process, such as membrane bioreactor, aerated biological filter and other processes. The use of a highly efficient aerobic treatment process with a filtration function can reduce the concentration of suspended matter and facilitate subsequent disinfection.

3.3 Scope of application

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

3.4 Simple biochemical treatment process

3.4.1 Process flow

The flow of simple biochemical treatment process is “biogas purification tank → disinfection”. The biogas purification tank is divided into a solid-liquid separation area, an anaerobic filter and a sedimentation filter area. The main functions of the three zones are to remove suspended solids, adsorb colloids and dissolved substances, further remove and degrade organic pollutants, and finally remove residual suspended matter and degrade organic pollutants through precipitation and filtration units to ensure the quality of the effluent. The biogas produced is treated differently according to the amount of gas. When the biogas produced by 1m3 sludge is more than 15m3, it is collected and used; when the biogas produced by 1m3 sludge is less than 15m3, it is collected and burned.

3.4.2 Process characteristics

Biogas purification tanks use the principle of anaerobic digestion to degrade solid organic matter. The treatment efficiency of biogas purification tank is better than that of decay tank and biogas tank, with low cost, low power consumption and simple management.

3.4.3 Scope of application

As a transitional measure for hospital wastewater treatment in remote mountainous areas and economically underdeveloped areas, gradually implement secondary treatment or primary treatment that strengthens the treatment effect.

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