©2018 Mahoning Valley Water Inc.  What Is Sulphur?      Sulphur is one of the most misunderstood contaminants in water.  It is characterized by that obnoxious “rotten egg” odor and is offensive at very low concentrations.  Because it is a gas, it is non-filterable and its’ strength (at the same location) varies with different environmental conditions.      Two forms of sulphur are commonly found in drinking water:  sulfate and hydrogen sulfide.  Neither form poses a health risk in normal concentrations.  In higher concentrations, however, hydrogen sulfide can be flammable (20 ppm) and even toxic (50 ppm).  High concentrations are rare in water.      Sulfate is a combination of sulphur and oxygen, part of naturally occurring minerals in some soil and rock.  The minerals dissolve over time and are released into ground water as a salt.      Hydrogen sulfide is produced by sulfate reducing bacteria (Desulfovibrio) which live in oxygen deficient environments such as deep wells, plumbing systems, and water heaters.  These bacteria form enzymes that accelerate the reducing of sulfates to sulfides by decreasing the activation energies required for the reduction to occur.  In plain words, sulfate salts are changed into hydrogen sulfide gas which has the obnoxious rotten egg odor.  Hydrogen sulfide gas also occurs naturally in some ground water.  It is found in both deep or shallow wells and often is present in wells drilled in shale or sandstone, or near coal or peat deposits or oil fields. Effects And Facts Of Sulphur Rotten Egg Odor—Sensory detection occurs as low as 0.05 ppm (parts per million).   Corrosivity—Sulphur is highly corrosive to metal plumbing and fixtures.  This corrosivity is generally proportional to the amount of sulphur but can be aggravated by pH, TDS (total dissolved solids), etc.  Evidence of this corrosion is “black water” described as periodic bursts of grey-black water coming out of the taps when first turned on.  The sulfide-induced corrosion flakes off the inside of the metal pipe or fixture.  If left uncorrected, this process will “thin-wall” the plumbing and cause leaks and serious damage.  This corrosion can also cause heavy metals such as copper and lead to leach into the water. Water Softeners—Sulphur can damage a water softener over time by causing chemical damage to the resin beads. Beverages & Foods—Sulphur adversely affects the taste and appearance of cooked foods, coffee, teas and other beverages. Stains—Sulphur can cause grey or black stains on kitchen and bathroom fixtures, and will tarnish silverware and discolor copper and brass utensils. Sulphur is a Gas—If left in an open container, it will dissipate in the air.  More gas will be released when the air is heavy.  The smell will be worse on cloudy days than on sunny days. Temperature—The solubility of sulphur decreases as temperature increases which is why the smell is always worse in hot water.   Sulphur Testing      Because hydrogen sulfide is treated in different ways, depending on the amount of sulphur present, an accurate test is very important.  The “nose knows” approach will tell if sulphur is present but a more sophisticated “gas release” test is necessary to determine the amount of sulphur for treatment purposes.  It is wise to test both cold and hot water to determine if the sulphur gas originates from the well or from the hot water tank.   Hot Water Sulphur      The method used to provide corrosion protection in most hot water tanks produces an environment that is ideal for the production of sulphur.  Modern water heaters are glass-lined to prevent corrosion, however, it is nearly impossible to assure 100% glass coverage especially as cracks may occur while the tank is in service.  In order to prevent tank corrosion where small cracks or voids in the glass coating may occur, a long magnesium rod or “anode” rod is used to provide cathodic protection.        Basically, due to the properties of magnesium and steel, the magnesium will corrode before the steel will.  As the magnesium rod dissolves, it gives off an abundance of electrons.  These electrons concentrate the corrosion forces to themselves, thereby protecting the steel tank and will do so until the magnesium rod is fully dissolved.        The amount of the electrons given off by the dissolving rod is far greater than what is needed to protect the exposed steel.  These excess electrons provide external energy that allow the sulfate reducing bacteria to convert sulfate salts to the hydrogen sulfide gas which, in turn, gives off the rotten egg smell.   Treatment Methods Hot Water Sulphur—Replace or remove the anode rod.  The magnesium rod can be replaced with a less reactive aluminum or copper rod.  Chlorinate and flush the hot water tank after removing or replacing the rod. Air Induction—Air induction systems add dissolved oxygen to the water allowing the sulphur to be oxidized.  Backwashing the filter removes the accumulated particulate matter. Iron / Sulphur Oxidizing Filter—An oxidizing filter (manganese dioxide based) may be used where concentrations of sulphur do not exceed 5 ppm and family size is not excessive.  The pH of the water should be above 6.8 and no sulfate reducing bacteria may be present.  The home well pump should be strong enough to effectively backwash the heavier material in the filter.   Chlorination / Dechlorination—When sulfate reducing bacteria is present, the family size is large, or when concentrations of sulphur exceed 5 ppm, a chlorination system is necessary.  Retention times and chlorine dosages must be calculated correctly. Other Treatment—Birm Filters, Carbon Filters and Ozone treatments may be effective under certain circumstances.