Hydrogen Sulfide

Hydrogen sulfide is a gas present in some water. There will never be a doubt when it is present as it smells strongly of "rotten eggs". It is often noticeable at levels as low as 1 mg/L.

Hydrogen sulfide presents two problems: it promotes corrosion due to its activity as a weak acid and high concentrations are both inflammable and poisonous. High concentrations of hydrogen sulfide can also foul the bed of an ion exchange softener. It is most common in deep-well water rather than surface water.

Low to moderate concentrations of hydrogen sulfide can be eliminated through the use of an oxidizing filtration, as is used to remove iron. Chemical treatment is not recommended for medium to high concentrations of hydrogen sulfide. In such cases, chlorine injection can be used or iron filtration with potassium permanganate. After the chemical injection feeder an activated carbon filtration is used to filter out the chlorine.

Many conditions can cause taste and odours in water, such as decayed organic matter, living organisms, chlorine, dissolved gases and high mineral concentrations. Water that contains hydrogen sulfide, for example, can cause an odour that is extremely obnoxious -- it will smell unmistakably like rotten eggs. The cause of the taste and/or odour should be determined before treatment is recommended.