Water Education - Water and Health


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Hydrogen Sulfidereverse osmosis banner square

Hydrogen sulfide is a gas present in some waters. There is never any doubt as to when it is present due to its offensive "rotten egg" odor. This characteristic odor is sometimes apparent in concentrations below 1 mg/l. Obnoxious as are the taste and odor of hydrogen sulfide, these are only two of the problems it presents. Hydrogen sulfide promotes corrosion due to its activity as a weak acid. Further, its presence in the air causes silver to tarnish in a matter of seconds. High concentrations of hydrogen sulfide gas are both flammable and poisonous. While such concentrations are rare, their presence in drinking water has been known to cause nausea, illness, and in extreme cases, death. High concentrations of dissolved hydrogen sulfide can also foul the bed of an ion-exchange softener. Its continued presence will lead to lower and lower capacity and may finally necessitate the replacement of the resin bed. Generally, hydrogen sulfide occurs in concentrations of less than 10 ppm (milligrams per liter). Occasionally the amount goes as high as 50 to 75 mg/l. Hydrogen sulfide is more common to well waters than to surface waters supplies.

There are several methods for removing hydrogen sulfide from the water. Most of them involve converting the gas into elemental sulfur. This insoluble yellow powder can then be removed by filtration. Low to moderate concentrations of hydrogen sulfide can be eliminated through the use of an oxidizing filter of the same type satisfactory for iron removal. Because the elemental sulfur precipitate tends to clog the filter material, it is usually necessary to replace this material from time to time.

Chemical treatment is recommended for medium to high concentrations of hydrogen sulfide. In such cases, solutions of household bleach or potassium permanganate serve as satisfactory oxidizing agents.

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