Hydrogen sulfide is a gas with a characteristic rotten-egg odor. In groundwater systems, it is common and originates from bacterial reactions with organic matter or hydrocarbons often associated with oil and natural gas. In groundwater, hydrogen sulfide may occur in water dissolved or as a gas. What kind of problems does hydrogen sulfide cause? Hydrogen sulfide is pungent to humans at low concentrations—often at levels above 0.03 parts per million (ppm). Human reactions to hydrogen sulfide may include:
Discomfort, at 0.04 ppm
Headaches, depression, dizziness, 0.08 to 2 ppm
Coughing, throat irritation, shortness of breath, 2.5 to 5 ppm
Nausea, vomiting, 0.32 to 20 ppm
Irritability, sleep loss, fatigue, memory loss, 0.32 to 20 ppm
Loss of appetite, weight loss, 0.7 to 40 ppm
Bronchitis, 10 ppm
Eye irritation, 10 to 20 ppm
Conjunctivitis and pain, 50 ppm for one-hour exposure
Eye damage, 50 to 100 ppm
Pulmonary edema (fluid in the lungs), 200 ppm
Death, 600 to 800 ppm.
Hydrogen sulfide forms an explosive mixture with air from 5.9 percent to 77.2 percent by volume. Ten (10) ppm is the standard concentration in air established by the federal Occupational Safety and Health Administration (OSHA) to trigger an on-site warning; 50 ppm is the standard for trigging emergency actions. Unless properly ventilated, hydrogen sulfide will remain in places such as a well house or pump house because it is heavier than air. Effects on well systems As little as 1 ppm can corrode iron, steel, copper, and brass found in pumps, faucets, appliances, and some well casings. Corrosion can leach metal into the water. Often high dissolved sulfide concentrations in a well can be reduced by mechanical cleaning of the well and disinfection that kills the type of bacteria that causes it. Sometimes a rotten-egg odor is present in hot water only. This could be caused by the reaction of sulfur ions in the water with a magnesium rod in the hot water tank. If so, these rods can often be replaced with aluminum fixtures or removed (check with the manufacturer) to eliminate the problem. Testing Testing is best done on site because hydrogen sulfide evaporates and oxidizes rapidly. If you buy a test kit, test immediately after collecting a sample. If using a laboratory, the lab will provide bottles with a stabilizing agent to ensure an accurate result.
Eliminating the problem Sometimes it is possible to deepen an existing well or drill a new well that yields water without unacceptable hydrogen sulfide levels. A gas-venting well cap also can be effective. In other cases, some form of water treatment may be needed. Among the technologies used are:
Aeration, which mixes air with water to separate out sulfide
Ion exchange in which a resin absorbs hydrogen sulfide
Manganese greensand filtration
Oxidizing filters that change the hydrogen sulfide to sulfur for removal
Ozone treatment that chemically separates sulfur for removal.
Always work with qualified water well system or water treatment professionals when considering well system modifications or water treatment. Learn more at www.WellOwner.org.
Water rights compilation available
A summary of groundwater rights in the United States, Who Owns the Water?, is available from the Water Systems Council through support by the U.S. Environmental Protection Agency. The report summarizes common law and statutory rules for groundwater rights in the 50 states and is intended for educational purposes only. An electronic version is available for download on the WSC website. Hard copies can be obtained by firstname.lastname@example.org.
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The Private Well Class: webinars and workshops
What Environmental Health Professionals Need to Know about Wells November 7, 2016 from 1-2:30 p.m. CDT The event has been submitted for pre-approval of 1.5 NEHA CE Credits and will be recorded. Register for the webinar
Private Well Assessment and Outreach for EHPs Learn private well fundamentals, how to assess a private well using the assessment tool, effectively engage private well owners, develop a program for outreach to well owners, and best practices for managing a well owner program.
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