WHAT ARE HYDROGEN SULFIDE AND SULFATE?

Hydrogen sulfide is not considered either a primary nor a secondary contami­nant in the Environmental Protection Agency’s current drinking water stan­dards, but if the concentration of hydrogen sulfide in water is more than 0.5 parts per million (ppm), it will:

  • Have an unpleasant odor (rotten egg)
  • Corrode iron, steel, copper and brass in well casing/plumbing/bathroom fixtures
  • Tarnish or discolor silverware, copperware and brassware
  • Stain laundry and bathroom fixtures yellow or black
  • Discolor beverages
  • Alter the appearance and taste of cooked foods

Sulfate is listed as a secondary contaminant with a secondary MCL (Maxi­mum Contaminant Level) of 250 ppm. High levels of sulfate above 250 ppm:

  • Impart bitter taste
  • Have a laxative effect
  • Cause dehydration
  • Can be especially detrimental to the health of infants and young animals

There are several treatment options for removing hydrogen sulfide and sulfate from household water. The type of treatment will depend on the concentration of hydrogen sulfide and/or sulfate in the water. Whether you need a point-of-entry (whole house treatment) or point-of-use (treatment at one faucet supplying water for drinking and cooking) system also depends on the concentration. If the concentration is high, a whole-house treatment is usually recommended. For this article however, we are going to focus on the use of GAC (granular activated carbon) and Catalytic Carbon for the removal of hydrogen sulfide and sulfate.

Granular Activated Carbon (GAC)

If the hydrogen sulfide level in your water is less than 0.3 ppm, a granular activated carbon (GAC) filter will reduce the unpleasant odor and taste. Be­cause of its limited capacity to adsorb hydrogen sulfide, a GAC filter may be exhausted quickly. As a result, activated carbon may not be effective for remov­ing concentrations of hydrogen sulfide in drinking water greater than 0.3 ppm. These filters can also remove tannins, trichloroethylene and other dissolved organic compounds.

Catalytic Carbon

Catalytic carbon has all of the adsorptive properties of conventional GAC but it can also convert hydrogen sulfide to elemental sulfur. The initial step in the treatment process is adsorption of hy­drogen sulfides onto the carbon surface; the subsequent step is the oxidation of adsorbed hydrogen sulfide to elemental sulfur in the presence of dissolved oxygen. In this capacity, catalytic carbon is similar to manganese greensand and chlorination systems that remove sulfides through oxidation. As a result, catalytic carbon units can be used to treat much higher hydrogen sulfide con­centrations than ordinary GAC filters. It differs in that it maintains a consistent catalytic activity (oxidation) to treat sulfur water without the use of chemical ad­ditives.