At different stages of sewage treatment, various combustible, toxic, and harmful gases such as methane, hydrogen sulfide, and ammonia are produced. These gases will greatly endanger the health and well-being of workers, and it is extremely important to choose gas detectors suitable for sewage treatment processes.

1、 Introduction to sewage treatment process

At present, the mainstream process of sewage treatment plants is anaerobic anaerobic aerobic process (AAO). The AAO process is suitable for secondary wastewater treatment, tertiary wastewater treatment, and reclaimed water reuse, and can simultaneously remove nitrogen, phosphorus, and organic matter.

1. Pre processing stage

After entering the sewage treatment plant, the raw water first enters the coarse grid sewage lifting pump room. After the coarse grid intercepts larger suspended solids, it is transferred to the fine grid pump room to further remove smaller suspended solids. Subsequently, the sewage enters the aeration sedimentation tank to remove organic matter from the gravel, and finally enters the sand water separator for separation. The sand is transported out of the factory, and the separated wastewater enters the next step.

2. AAO processing stage

In sewage, nitrogen mainly exists in the form of ammonia nitrogen and organic nitrogen. Therefore, an anoxic section is set up at the front end of the anaerobic section of the AAO process, and the sludge in the anoxic section is refluxed for denitrification reaction, ultimately achieving the goal of denitrification.

3. Deep processing stage

4. Sludge treatment stage

The mixed odor enters the deodorization room through the ventilation duct in the sludge buffer tank for activated carbon deodorization, while the sludge enters the sludge dewatering room. After adding flocculant through the feeding machine, it is transferred to the centrifugal pump for dewatering. After dewatering, it enters the sludge storage bin and is discharged and transported away through the discharge port.

2、 Main hazards

1. Poisoning and suffocation

During the sewage and sludge treatment stage, toxic gases such as ammonia, hydrogen sulfide, and hydrogen chloride (sodium hypochlorite decomposition) are mainly produced during the process of decomposing sewage and sludge. Under normal production conditions of the sewage treatment plant, the staff mainly carry out inspection operations. When staff enter process sections such as grid rooms, sand removal rooms, and secondary sedimentation tanks, there may be a risk of poisoning.

In addition, during equipment maintenance and dredging of treatment tanks, equipment, pipelines, etc., due to limited or enclosed space, operators may encounter dangers such as suffocation and hydrogen sulfide poisoning.

2. Burning and explosion

Methane accumulation is prone to occur in spaces with poor ventilation, such as pipelines, trenches, and storage yards, where sewage and sludge are stored. When exposed to a source of fire, it can lead to fires and explosions.

3、 Selection of combustible gas toxic gas detector

When selecting gas detectors for common harmful gases in sewage treatment plants, staff should prioritize detecting combustible gases (methane), oxygen, hydrogen sulfide, ammonia (optional), and hydrogen chloride (optional). The main performance indicators are as follows:

Fixed gas detector:

according toGBZ 1-2010 "Hygienic Standards for the Design of Industrial Enterprises" and GBZ/T 223-2009 "Specification for the Installation of Toxic Gas Detection and Alarm Devices in the Workplace"Requirement: For indoor workplaces that may suddenly release large amounts of harmful substances or easily cause acute poisoning or flammable and explosive chemicals during production, toxic gas alarms or flammable gas alarms should be installed and interlocked with the accident exhaust system.

When working in a confined space, a pump suction gas detector should be used. After sampling and testing to ensure safety, personnel can enter the work.