Saturday, December 21, 2013

Hydrogen Sulfide Reduction In Waste Water Collection Systems

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.

Chemical treatment is the other way of control used by specialists. The chemical compounds used mostly are chlorine compounds such as bleach, ferric chloride, sodium and calcium hypochlorite. When any of these are added to the sewer system, work by oxidizing sulfides hence the gas will not be formed at all.

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.

The last measure is through the use of a monitoring meter known as the liquid phase sulfide meter to measure amount of sulfide in wastes that come from industries. Therefore when the sulfides are above a certain measure, the wastes have to undergo pre treatment process first they are taken to the sewer system. From this article, we learn on the different measures of hydrogen sulfide reduction in waste water collection systems. Specialists are still researching on other advanced methods to curb this problem.




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