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.

There is thus need to control the production of this gas in waste water collection system to very low levels. One way which specialists have found to reduce production of this gas is through addition of a strong alkali or soluble basic solution. The basic solution for instance sodium hydroxide (NAOH) or magnesium hydroxide when added to sewage increases the pH and this leads to limited formation of the 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.

But with this chemical treatment, certain requirements have to be met. First there needs to be a feed system established from which the chemicals are pumped into the waste water. This feed system might take some time and even money to be established. Another thing is that the feeding system needs to be monitored constantly to ensure it is working well. At all times, safety measures must always be considered.

When it comes to corrosion problems there are certain measures that are taken to reduce or prevent this. Increasing ventilation in the sewer infrastructure to prevent break down of organic matter conditions with no oxygen is one way. The other way is through the use of protective coatings on tanks and sewer pipes on their inner part. These coatings are usually composed of tar products, polythene linings, vinyl, cement, plastics and many other materials.

Yet another method of corrosion control is by spraying the crown and manhole. At the crown of a pipe is where rust is mostly at its worst because the acid collects on this area. The effect of this is weakening and collapse of the pipe. The agent that is sprayed on these structures is known as Sulfa Lock Gel and this one guards the surfaces from intense acid effects.

Lastly, a monitoring instrument called the liquid phase sulfide meter has been formulated to help in observing sulfides levels in industrial wastes. If the instrument shows the sulfide to be higher than the wanted amount, the waste undergoes pre treatment before its release to the waste water collection system. All in all, these strategies on hydrogen sulfide reduction have helped a lot in control of the negative effects of the gas. But specialists are still coming up with other methods to manage this issue more effectively.




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