Sulfates and Hydrogen Sulfide
Sulfates are a combination of sulfur and
oxygen (SO4, SO3) and are a part of naturally
occurring minerals in some soil and rock formations that contain
groundwater. The mineral dissolves over time and is released into
Sulfur-reducing bacteria, which use sulfur
as a food source, are the primary producers of large quantities of
hydrogen sulfide (H2S). These bacteria chemically change
natural sulfates (SO4) in water to hydrogen sulfide.
Sulfur-reducing bacteria live in oxygen-deficient environments such as
deep wells, plumbing systems, water softeners and water heaters. These
bacteria strip the O2 molecule from the sulfate ion to leave
(S) which combines with Hydrogen in water to form H2S.
These bacteria usually flourish in large recirculating water tanks and
Hydrogen sulfide gas also occurs naturally
in some groundwater. It is formed from decomposing underground deposits of
organic matter such as decaying plant material. It is found in deep or
shallow wells and also can enter surface water through springs, although
it quickly escapes to the atmosphere. Hydrogen sulfide often is present in
wells drilled in shale or sandstone, or near coal or peat deposits or oil
is a powerful oxidizer that
can destroy the sulfur reducing bacteria, this will reduce odors emanating
from your water and improve water quality. Air Stripping is another
common method used to remove H2S odors from water. See
our air-stripping injection
Sulfate minerals can cause scale buildup in
water pipes similar to other minerals and may be associated with a bitter
taste in water that can have a laxative effect on humans and young
livestock. Sulfur-oxidizing bacteria produce effects similar to
those of iron bacteria. They convert sulfide into sulfate, producing a
dark slime that can clog plumbing and/or stain clothing. Blackening of
water or dark slime coating the inside of toilet tanks may indicate a
sulfur-oxidizing bacteria problem. Sulfur-oxidizing bacteria are less
common than sulfur-reducing bacteria.
Hydrogen sulfide gas produces an offensive
"rotten egg" or "sulfur water" odor and taste in the
water. In some cases, the odor may be noticeable only when the water is
initially turned on or when hot water is run. Heat forces the gas into the
air which may cause the odor to be especially offensive in a shower.
Occasionally, a hot water heater is a source of hydrogen sulfide odor. The
magnesium corrosion control rod present in many hot water heaters can
chemically reduce naturally occurring sulfates to hydrogen sulfide.
A nuisance associated with hydrogen sulfide
includes its corrosiveness to metals such as iron, steel, copper and
brass. It can tarnish silverware and discolor copper and brass utensils.
Hydrogen sulfide also can cause yellow or black stains on kitchen and
bathroom fixtures. Coffee, tea and other beverages made with water
containing hydrogen sulfide may be discolored and the appearance and taste
of cooked foods can be affected.
High concentrations of dissolved hydrogen
sulfide also can foul the resin bed of an ion exchange water softener.
When a hydrogen sulfide odor occurs in treated water (softened or
filtered) and no hydrogen sulfide is detected in the non-treated water, it
usually indicates the presence of some form of sulfate-reducing bacteria
in the system. Water softeners provide a convenient environment for these
bacteria to grow. A "salt-loving" bacteria, that uses sulfates
as an energy source, may produce a black slime inside water softeners.
Sulfate may have a laxative effect that can lead to
dehydration and is of special concern for infants. With time, people and
young livestock will become acclimated to the sulfate and the symptoms
disappear. Sulfur-oxidizing bacteria pose no known human health risk.
The Maximum contaminate level is 250 mg/L.
Hydrogen sulfide is flammable and poisonous. Usually
it is not a health risk at concentrations present in household water,
except in very high concentrations. While such concentrations are rare,
hydrogen sulfide's presence in drinking water when released in confined
areas has been known to cause nausea, illness and, in extreme cases,