Hazard identification and control in sewage treatment plants!

Pay more attention to the public account: environmental protection water treatment

In addition to ensuring the normal discharge of effluent up to the standard, the safe operation of the sewage treatment plant is very important. Therefore, the focus of safety management in sewage treatment plants is to control dangerous point sources in a safe state and controllable range. The risk factors of sewage treatment plants will be slightly different due to the characteristics of sewage and sludge treatment processes, equipment selection, elevation design, and location.

1. Process flow and structure of sewage treatment plant

With the promulgation of the "Pollutant Discharge Standard for Urban Sewage Treatment Plants" (GB18918-2002) in December 2002, the sewage treatment technology has developed from only focusing on the removal of organic matter in the past to having the function of phosphorus and nitrogen removal. Many new technologies, new processes and new equipment have been introduced abroad, and AB method, oxidation ditch, A/O process, A/A/O process, SBR, CASS and other processes have been widely used in mainland urban sewage treatment plants, and imported grids, pumps, blowers, dehydrators, agitators and other equipment are widely used. The main structures include metering wells, coarse inlet grids, inlet pump rooms, fine grids, grit tanks, primary sedimentation tanks, biological reaction tanks, distribution wells, secondary sedimentation tanks, effluent pump rooms, sludge thickening tanks, sludge storage tanks, sludge pump rooms, sludge digesters, dewatering machine rooms, sludge silos, biogas compressor rooms, and biogas generator rooms. The main buildings include office buildings, substations, blower rooms, chlorination rooms, dosing rooms, dehydration machine rooms, etc.

Main teams: central control room, sewage treatment class, sludge treatment class, total substation, laboratory, machine repair class, warehouse, driver class.

2. Identification and distribution of hazards

According to the design and operation of sewage treatment plants, the major dangerous point source hazards are mainly there.

1. Distribution of occupational poisoning hazards.

The source water of the sewage plant comes from the municipal domestic sewage and industrial wastewater, which is already in a state of anoxic when it is transported in the municipal pipe network, and the toxic and harmful gases such as hydrogen sulfide and biogas in the sewage will be generated, dissolved, deposited or overflowed during the treatment process, so poisoning events will occur when the staff enter the following areas: water inlet grid, submersible pump room, grit tank, water distribution well, process gate well and box culvert, mud storage tank, digester, biogas cabinet, dewatering machine room, rain and sewage pipeline and inspection well. Liquid chlorine, sulfuric acid, chemical flocculants used in the production process and analytical reagents used in laboratories are released or inhaled by the human body.

2. Distribution of electric shock hazards.

The sewage treatment plant is a large electricity consumer, designed with a high and low voltage substation and distribution system, about 300 sets of control boxes of equipment, and the operator is prone to electric shock casualties due to improper operation, equipment failure and grounding lightning protection system in the process of maintenance and operation. The main parts are: high and low voltage substation, inlet pump room distribution room, dosing room distribution room, blower room distribution room, ultraviolet disinfection canal distribution room, sludge control room distribution room, dehydration machine room distribution room, central control room, equipment control box

3. Distribution of fire hazards.

In addition to the process structure, the sewage treatment plant also supports the construction of ancillary structures, which not only store flammable materials, but also the construction materials are flammable, and fire hazards will occur when the structure power supply is aging, lightning strikes, improper use of electrical appliances, open flame operations and other unsafe behaviors: warehouse, comprehensive office building, high and low voltage substation, training building, access pump room, machine repair workshop, blower room, dosing room, sludge control room, dewatering machine room.

4. Distribution of explosion hazards.

The biogas produced in the sludge digestion process is not only a toxic and harmful gas, but also a flammable and explosive gas, so the staff must take effective measures when entering the digester, biogas cabinet and sludge control room area, and the fire order issued by the security and safety technology department can only be operated. Equipment with high-pressure vessels or pipelines used in the production process (dehydrator room, air compressors, blowers, high-density pumps) may explode due to the failure of safety devices.

5. Distribution of drowning hazards.

The process of sewage treatment requires a certain residence time, and the effective water depth of the treatment structure is generally 3~6 meters. The main structures are: inlet grid channel, grit tank, primary sedimentation tank, raw and negative tank, secondary sedimentation tank, disinfection tank (channel), inlet and outlet pump room collection tank, mud storage tank.

6. Distribution of falling hazards.

The structure of sewage and sludge treatment has the characteristics of large volume, in order to ensure that the treatment process realizes gravity flow, the top of the structure is generally 2~3 meters from the ground during the elevation design, and some structures will reach more than 10 meters, and the pool depth of the structure is generally 3~7 meters, and the operator accidentally falls into the pool or on the ground, which may cause a fall accident. The main structures are: inlet grid channel, grit tank, primary sedimentation tank, bio-reaction tank, secondary sedimentation tank, disinfection tank (channel), pump room collection tank, sludge storage tank, digester, biogas cabinet, sludge silo.

7. Distribution of mechanical injury hazards.

Sewage treatment is a mechanized and automated production process, and each sewage treatment plant has thousands of sets of mechanical equipment (coarse grid and press, fine grid and press, primary sedimentation tank scraper, blower, secondary sedimentation tank scraper, dosing pump, digester sludge pump, dehydrator mud pump, high-density pump, crane, electric gate), and its rotating parts will cause mechanical injury to personnel, and the lifting injury will be caused by the lifting of items hoisted by the crane or the breaking of the wire rope.

3. Management and control of hazards

Safety management is a systematic work, not only to establish a safety management organization, implement the safety production responsibility system, carry out effective safety inspection, education, training, prepare and implement various safety operation procedures and technical operation procedures, and formulate various safety emergency plans, so that everyone understands safety and everyone will be safe. Moreover, it is necessary to manage and control the dangerous point sources of sewage treatment plants, and take necessary technical measures to control them, so as to ensure that people, objects and the environment are in a safe state.

1. Control measures for occupational poisoning hazards:

(1) Set up toxic and harmful gas detectors, automatic alarm instruments, safety belts, safety ropes, air respirator safety equipment and personal protective equipment.

(2) Protective masks and gloves must be worn during operation and rescue.

(3) Set up necessary ventilation equipment.

(4) Set up safety warning signs at the source of danger.

2. Control measures for electric shock hazards:

(1) Regularly inspect and inspect electrical equipment.

(2) Strengthen the insulation protection of electroscopes, insulating boots, insulating gloves, insulating rubber, etc., and do a good job of grounding protection.

(3) Regularly inspect the lightning protection and grounding system.

(4) Install a leakage protector.

(5) Use electrical facilities that meet the specifications.

(6) Compile safety operation procedures, adhere to the job training of electrician operators, and take up posts with certificates.

(7) Set up safety warning signs at the location of the hazard source.

3. Control measures for fire hazards:

(1) Regularly inspect, inspect, maintain and replace fire-fighting equipment and equipment.

(2) Regularly inspect the fire protection system and structure facilities.

(3) Replace the fire extinguisher regularly.

(4) Use fire-fighting facilities that meet the specifications.

(5) Implement the fire order system.

(6) Strengthen personnel training.

(7) Set up safety warning signs at the source of danger.

4. Control measures for explosion hazards:

(1) Regularly inspect pressure vessels, pressure gauges, safety generators, and pressure relief devices.

(2) Strengthen the operation and maintenance of electrical equipment.

(3) Regularly inspect and detect hazards.

(4) Compile safety operation procedures and strengthen personnel training.

(5) Set up safety warning signs at the source of danger.

5. Control measures for drowning hazards:

(1) Regularly overhaul protective railings.

(2) Equipped with life-saving equipment such as safety belts, safety ropes, lifebuoys, and life jackets.

(3) Remove the stagnant water, snow and debris on the pool in time.

(4) Compile safety operation procedures and strengthen personnel training.

(5) Set up safety warning signs at the source of danger.

6. Control measures for falling hazards:

(1) Regularly overhaul ladders, protective railings, and baseboards.

(2) Equipped with life-saving equipment such as safety belts, safety ropes, lifebuoys, and life jackets.

(3) Remove the stagnant water, snow and debris on the pool in time.

(4) Strengthen personnel training and improve attention.

(5) Set up safety warning signs at the source of danger.

7. Control measures for mechanical injury hazards:

(1) Regularly inspect and inspect the transmission parts of the equipment.

(2) Strengthen the safety protection device of exposed moving parts.

(3) Regularly inspect special equipment such as cranes and forklifts.

(4) Strengthen the training of special operators of field trucks and forklifts, and take up posts with certificates.

(5) Prepare safety operation procedures.

(6) Set up safety warning signs at the location of the hazard source.

The safety control of the sewage treatment process should be effectively prompted according to the status of safety risks. It is necessary to take necessary technical and engineering measures to strengthen the repair and maintenance of equipment and facilities and ensure that they are in good condition. Strengthen team safety management, implement the post safety responsibility system, and strictly implement safety and technical operation procedures to ensure normal production and operation.