Q and A: I have an open aerator on my water system that now smells like rotten eggs. Do you have any ideas for troubleshooting this problem?

from G.M., via e-mail

Hydrogen sulfide or sulfur is a naturally occurring contaminant, which gives water a disagreeable “rotten egg” odor and taste. Hydrogen sulfide is a gas that is found in well water and makes water corrosive to metals, tarnishes copper and silverware, and produces slugs of black material that stains laundry and porcelain at concentrations as low as 1.0 milligram per liter (mg/l). Hydrogen sulfide is detectable by most people at 0.1 mg/l and is usually caused by certain types of bacteria that may be present in the ground water. These bacteria form hydrogen sulfide from organic matter or from sulfates, sulfides, and sulfur itself.

For those considering hydrogen sulfide removal equipment, have a good water analysis completed to determine other water characteristics such as iron content, pH, and hardness that may influence the type of equipment used. Suppliers of such equipment will usually analyze water free of charge. If you are having an independent test completed specifically for hydrogen sulfide, check with the testing lab because this test usually requires a special sample bottle with an additive to prevent loss of the dissolved gas before the sample reaches the lab.

There are no known health effects caused by hydrogen sulfide. However, in high concentrations it affects the palatability of the water. In reconstruction of an existing well, hydrogen sulfide gas can accumulate in excavations since it is heavier than air. In such concentrations this can be dangerous to anyone working in the well.

Equipment for hydrogen sulfide removal can be selected after a proper water analysis and interpretation of the water analysis report. There are generally three types of hydrogen sulfide removal equipment:

  1. chlorination followed by filtration,
  2. filtration with a manganese greensand filter, or
  3. aeration.

Aeration, the method in question, can be used to oxidize and remove hydrogen sulfide by forcing air into a pressure tank with an air compressor or by spraying water into a cistern or other non-pressurizing storage tank. There is usually an offensive odor around the aerator, and unless the aerator is a pressurized type, a second pump is needed. Filtration is often needed after aeration.

Aerators, like most water equipment, require some maintenance. First, clean the aerator thoroughly with a 10% Clorox solution using a long handled brush. Slime may build up in the aerator and cause it to function improperly, hence not removing the hydrogen sulfide. Second, check to be sure the nozzles are spraying a fine mist when the pump is running (if applicable). If everything seems to be in order and you are still experiencing problems you will need to call to have the aerator serviced and/or to replace malfunctioning parts.

If you purchase equipment, make sure to find a reputable dealer who has training and experience with this problem and who can provide proper installation and service. Also, ask about how to maintain and service the equipment on your own. Always get more than one opinion about the matter because most dealers would like to sell you their products. Make sure the equipment comes with a performance guarantee for specific water properties. Some situations (extremely poor water properties detected) may require equipment to be used on a trial basis. In other cases it may be less expensive and troublesome to rent equipment with a service contract than to actually buy it. It is up to you to make the best decision for your situation.