The sulfate content in domestic sewage is usually between 20 and 10 mg / L, and industrial wastewater directly entering the human drainage system will significantly increase the sulfate content in the water. Because hydrogen sulfide corrosion occurs on the inner surface of sewage pipes, people do not get enough attention.
Once the pipeline structure is seriously corroded and damaged, it will cause major accidents such as road surface collapse and sewage overflow, affecting the city's production and life. A large amount of capital is required to repair these pipes damaged by corrosion. Hydrogen sulfide corrosion in sewage pipes is a widespread phenomenon, and the losses caused by it are huge.
Therefore, it is very important to understand the mechanism of this corrosion and master the prevention and control measures. Under anaerobic conditions, anaerobic microorganisms reduce the sulfates in sewage to sulfides and combine with the hydrogen ions in the water to produce hydrogen sulfide. The hydrogen sulfide gas escapes from the sewage and dissolves in the condensed water on the inner surface above the water level of the sewage pipe.
Generally, sulfuric acid corrosion is the main cause of pipeline corrosion, while hydrogen sulfide has a much smaller direct corrosion effect. The rate of hydrogen sulfide corrosion is affected by many factors, including sewage water quality and pipeline materials.
In addition to the above factors, there are other factors that affect the hydrogen sulfide corrosion of the pipeline. Appropriate pipe slope can reduce the sludge layer on which microorganisms depend; the turbulence of sewage in the pipe will increase the Do value. The humid environment in the space above the water level of the pipeline is a necessary condition for the conversion of gas phase HZS to HZSO4. Keeping the pipeline above the water level dry or full of pipeline flow can reduce the corrosion of hydrogen sulfide. Pipes are also factors that affect corrosion. Most gravity drainage pipes are concrete pipes or cast iron pipes. These pipes are susceptible to acid corrosion.
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