Advanced Water
Hydrogen Sulfide (H2S)

Water that is giving off a distinctive odor is often contaminated with hydrogen sulfide. Hydrogen sulfide
does not usually pose immediate health problems at the levels it is found in domestic drinking supplies.
However, it is certainly an inconvenience — especially to one's nose.

Being informed is always an important step in safety issues. What follows are answers to popular hydrogen
sulfide questions.

What is hydrogen sulfide, and how does it form?
Sulfur-reducing bacteria present in ground water use sulfur as an energy source to chemically change
sulfates to produce hydrogen sulfide. The bacteria uses sulfur from decaying plants, rocks, or soil. They
exist in environments that are oxygen-deficient such as deep wells and plumbing systems.

However, hydrogen sulfide can exist naturally in ground water as well. It can enter surface water through
springs and quickly escape into the atmosphere. Hydrogen sulfide crops up other ways too. The
magnesium rod used in water heaters for corrosion control can chemically reduce sulfates to hydrogen
sulfide, and sewage pollution can be a source.

How can hydrogen sulfide affect one's health?
Hydrogen sulfide can be toxic, but its strong odor usually allows for detection long before it reaches
extreme levels. Hydrogen sulfide is flammable and poisonous. Such concentrations are not common, but if
the gas is released in a confined area it can cause nausea, illness, and—in extreme situations—death.
What effects does hydrogen sulfide have on the environment?
Hydrogen sulfide can be corrosive to metals such as iron, steel, copper, and brass, and it can cause
yellow or black stains on kitchen and bathroom fixtures. It can discolor and alter the taste of beverages
and food prepared with contaminated water.

How can hydrogen sulfide be detected?
The nose is the best source. Hydrogen sulfide is one of the few water contaminants that human senses
can detect at low concentrations. The odor is most noticeable when water is first turned on or heated.
Thus, a shower can be an unpleasant experience.

The odor can be detected at levels as low as 0.5 parts per million. At less than 1 ppm, hydrogen sulfide will
give water a musty odor. At 1 to 2 ppm, it will have an odor similar to rotten eggs. Levels are usually less
than 10 ppm.

Since hydrogen sulfide is dissolved in water and vaporizes from it, samples must be analyzed at the site or
stabilized before sending them to a laboratory. Several test kits are available for less than $10.

How can hydrogen sulfide be treated?
There are various methods. They should be chosen based on the level of hydrogen sulfide, the amount of
water being treated, the levels of iron and manganese, and bacterial contamination. Hydrogen sulfide can
be reduced or removed by activated carbon filtration, shock chlorination, oxidizing chemical injection,
oxidizing filtration, and water heater modification.

Hydrogen sulfide reduction methods:
  • Activated carbon filters are good when hydrogen sulfide is present in low levels. The hydrogen
    sulfide is absorbed onto the surface of the carbon particles.
  • Shock chlorination may reduce, but not eliminate, the hydrogen sulfide-producing bacteria. It
    involves mixing a sufficient amount of a chlorine-based chemical with the water to create a solution
    containing 200 ppm of chlorine throughout the water system. It is left in the system for several hours.
    The system must be flushed with fresh water when the process is complete.
  • Oxidation removes hydrogen sulfide concentrations exceeding 6 ppm. It can be done by aeration,
    chlorination, ozone, and potassium permanganate. There should be at least 20 minutes of contact
    between the chemical and the water.
  • Oxidizing filters will work for concentrations up to 6 ppm. The filter contains sand with a manganese
    dioxide coating that changes hydrogen sulfide gas to tiny particles of sulfur that are trapped inside
    the filter.
  • Water heater modification is necessary when hydrogen sulfide is causing an odor within the water
    heating system. Replacing the magnesium corrosion control rod with one made of aluminum or other
    metals usually improves the situation.
Advanced Water Products & Services
7280 Caswell Street
North Syracuse, NY 13212
(315) 451-2233 phone
(315) 458-0526 FAX
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