Important Information On Hydrogen Sulfide Reduction In Sewage System

By Harriett Crosby


Hydrogen sulfide is a colorless gas produced when organic matter is being broken down by bacteria in absence of oxygen. This procedure is usually referred to as anaerobic digestion and can occur in swamps and sewers. It can also occur naturally as natural gas or in volcanic gases. This gas has a characteristic smell of rotten eggs no wonder the foul smell usually produced by sewers. It is no wonder specialists are concerned with hydrogen sulfide reduction in the sewer system.

There are usually a lot of concerns among environmental specialists with the production of this gas in the sewage system. This is because it contributes greatly to the rust problems in the sewer structures and also people living near sewage systems always complain of odor problems. For people wondering how corrosion comes about, it results when the sulfide gas produced combines with water in the system resulting to formation of hydro sulfuric acid that corrodes infrastructure.

These negative effects of the gas to sewage system and the environment led to certain control measures to be devised. These measures were to reduce and ultimately control production of this gas. The first method of control is addition of a strong alkali such as magnesium hydroxide or sodium hydroxide to the waste water. The effect of this is increase of the sewer pH and thus limited formation of the sulfide gas.

Another way devised to control the odor problems is through addition of chemical compounds also known as chemical treatment. The most used compounds in this treatment are chlorine compounds like sodium hypochlorite, calcium hypochlorite, ferric chloride and bleach. They are added to the sewage and they oxidize the sulfides hence preventing formation of the gas.

However this addition of chemical compounds can be challenging when there is no pumping post from which the chemicals are fed into the system. Therefore a chemical feed system should be established to make this process easier. The feed system should also be monitored to ensure effective treatment system. Safety measures are usually considered when carrying out this chemical treatment.

For the rust problems, several measures exist to control this. The first one involves increased ventilation in sewer system to allow aerobic digestion to occur rather than anaerobic. The other measure is use of protective coatings when manufacturing sewer pipes and tanks. These coatings can be polythene linings, cement, vinyl, tar products and the do prevent corrosion of the infrastructure.

The other method of corrosion control is crown and manhole spraying. Usually, corrosion is worst at the crown of the pipe since the acid collects at this point. This causes the pipe to weaken and eventually collapse if the problem is persistent. Spraying a Sulfa Lock Hi Gel onto the manhole and sewer surfaces protects them from harsh effects of the acid.

There is also a monitoring instrument known as a liquid phase sulfide meter that monitors the amount of sulfides in industrial wastes. When the sulfide content is beyond the required amount, the industrial discharge undergoes pretreatment before being released to sewer system. All these control strategies used in hydrogen sulfide reduction in sewers work together to prevent corrosion and odors. Scientists are however still coming up with new chemicals and instruments to effectively manage this problem.




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