On Line Monitoring - Hydrogen Sulphide

Overview

Following a review of the materials that we handle and in light of experience on other treatment plants we identified the potential for Hydrogen Sulphide gas to be present in certain materials.

Hydrogen sulphide is a very common gas which is present in a lot of natural materials - for example it is commonly found on farms e.g. to quote a leading website for farmers "Liquid manure storage systems have come into prominent use in recent years. Many dairy, beef and hog operations (and to a limited extent poultry operations) now use liquid manure systems as a fast and economical method of handling animal wastes. These systems, particularly if they are incorporated into the barn construction, may pose a serious hazard because of gases produced. Decomposing animal manure gives off a variety of gases including hydrogen sulphide, carbon dioxide and methane. Of all these gases, hydrogen sulphide or more commonly called manure gas, is the most dangerous. Hydrogen Sulphide (H₂S) has been responsible for many animal deaths as well as occasional human deaths".

It is further commonly found in landfill leachates, waste treatment plants and also in some chemical wastes.

We have always had the ability to test for this as a gas in loads and tanks using portable equipment but at a Health and Safety Meeting agreed to install a Continuous Monitor on our main receiving tank for water based wastes which may contain this Gas - picture below

The monitor was installed in the Spring and we have further spare channels to add further monitors on our plant at a later date if required

More details on Hydrogen Sulphide

PROPERTIES OF HYDROGEN SULPHIDE

Hydrogen sulphide is a clear, colourless gas that can be identified in relatively low concentrations, by a characteristic "rotten-egg" odour. Hydrogen sulphide is approximately 20 percent heavier than air, with a specific gravity of 1.19. Hydrogen sulphide odours can be recognized in concentrations of less than 1 mg/kg (air). The odour of hydrogen sulphide will increase as the gas becomes more concentrated. However, in concentrations of 150 or greater mg/kg (air), a person's ability to detect the gas is affected by temporary paralysis of the olefactory nerves in the nose. Owing to this unique property of Hydrogen sulphide, relying totally on the sense of smell to warn against the gas, can be extremely dangerous. In high concentrations, the ability to smell the gas is lost instantaneously, the disappearance of the odour could mean that the gas concentrations have increased.

PHYSIOLOGICAL EFFECTS OF HYDROGEN SULPHIDE

Hydrogen sulphide is classified as a toxic chemical, in high concentrations it will lead to almost instantaneous poisoning and death. High concentrations will result in the complete arrest of respiration. A person over come by this gas should promptly be removed from the contaminated area and given immediate artificial respiration.

Exposure to lesser concentrations may result in nausea, stomach distress, belching and coughing. Moderate concentrations may result in eye irritation.