Well Water Quality Problems – Hydrogen Sulfide

No one wants to smell foul odors coming from the faucet when they turn on the water, yet homes across New England commonly face this problem due to the growth of naturally-occurring bacteria and hydrogen sulfide gas. It is easily identified by its rotten egg smell, and can be removed with the installation of a water filtration system.


What is hydrogen sulfide?

Hydrogen sulfide is a colorless gas that can exist naturally in groundwater. It is most common in shales and sandstones and has been connected to groundwater with low pH and high levels of iron or manganese. Hydrogen sulfide is the result of sulfur-reducing bacteria present in groundwater using sulfur as an energy source to chemically change sulfates to hydrogen sulfide. These bacteria are often in oxygen-deficient environments where decaying plants and other organic matter are found, such as deep or shallow wells, plumbing systems, water heaters, and sewage pollution. Hydrogen sulfide also can even enter surface water through springs.


How does hydrogen sulfide impact my water quality?

It only takes a small amount of hydrogen sulfide in water before homeowners will be able to smell it. While these low levels are unlikely to pose any health risk, it can be harmful if the source of the rotten egg smell is from sewage contamination.



How a homeowner manages hydrogen sulfide contamination depends on the level of hydrogen sulfide, the amount of water being treated, the levels of iron and manganese, and the water pH, among other factors. Once these factors are determined, your well water technician should talk to you about filtration choices. This includes carbon filtration, shock chlorination, ion exchange, manganese greensand filtration, oxidation, oxidizing filtration, ozone treatment, and water heater modification.


For low levels of contamination, you may want to choose a granulated activated carbon filter system. The hydrogen sulfide is absorbed onto the surface of the carbon particles. Over time, the filters fill up with the contaminant and must be replaced. Filters left in the system too long can harbor sulfate-reducing bacteria.


If the source of the hydrogen sulfide causing bacteria is your well or water heater, shock chlorination may reduce the hydrogen sulfide-producing bacteria.  It’s most effective in water with a pH between 5 and 7. This process can take hours to a few days, depending on a concentration of chlorine in the water, water temperature, and pH. An activated carbon filter may be necessary to remove residual chlorine or small amounts of remaining hydrogen sulfide.


An ion exchange resin can be effective in absorbing hydrogen sulfide, such as a water softening system. The resin removes the contamination until the resin is exhausted, then the resin is regenerated with salt.  Suspended solids and precipitated iron can clog the unit and may require an additional pretreatment system. Filters used to remove iron and manganese can also be useful with small concentrations of hydrogen sulfide.  These systems are specialized and require frequent maintenance.


Oxidation removes hydrogen sulfide in larger concentrations. It can be done by aeration, chlorination, and potassium permanganate. Oxidizing filters contain sand with a manganese dioxide coating that changes hydrogen sulfide gas to tiny particles of sulfur that are trapped inside the filter. Another option for large amounts of hydrogen sulfide is ozone treatment, which creates a chemical reaction that precipitates sulfur.


Water heater modification may be necessary when hydrogen sulfide is causing an odor within the water heating system, especially if the contamination continues to return after treatment. Replacing the magnesium corrosion control rod with one made of aluminum or other metals usually improves the situation. However, such action could void the manufacturer’s warranty on the water heater.


If your water smells like rotten eggs or sulfur, contact the well water technicians at Skillings and Sons for an estimate on a water treatment solution.