Sulfate is a naturally occurring anion in freshwater, both surface water and groundwater.   Thus, a major source of sulfate in domestic waste water is from the source water that was processed into tap/drinking water and then became waste water.  There is general information on sulfate in this document: USEPA (U.S. Environmental Protection Agency). 2003b. Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Sulfate. www.epa.gov/safewater/ccl/pdf/sulfate.pdf; EPA 822-R-03-007. Washington DC.

Concerning sulfate concentrations, these vary depending on the geology and region.  It is common for sulfate concentrations to be between 10-50 mg/L in freshwater, although some water sources can have higher concentrations.

Industrial inputs can also contribute sulfate to waste water.

Sulfate is a naturally occurring anion in freshwater, both surface water and groundwater.   Thus, a major source of sulfate in domestic waste water is from the source water that was processed into tap/drinking water and then became waste water.  There is general information on sulfate in this document: USEPA (U.S. Environmental Protection Agency). 2003b. Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Sulfate. www.epa.gov/safewater/ccl/pdf/sulfate.pdf; EPA 822-R-03-007. Washington DC.

Concerning sulfate concentrations, these vary depending on the geology and region.  It is common for sulfate concentrations to be between 10-50 mg/L in freshwater, although some water sources can have higher concentrations.

Industrial inputs can also contribute sulfate to waste water.

Thank you very much Prof. Andrea M Dietrich for your help

Odor-producing substances found in domestic wastewater and sludge are small, relatively volatile molecules having molecular weights between 30 and 150 g/mole. Most of these substances result from anaerobic decomposition of organic matter containing sulfur and nitrogen. Inorganic gases produced from domestic wastewater decomposition commonly include hydrogen sulfide, ammonia, carbon dioxide, and methane.

Of these gases, only hydrogen sulfide and ammonia are malodorous. Often, odor-producing substances include organic vapors such as indoles, skatoles, mercaptans and nitrogen-bearing organics.

Hydrogen sulfide is the most commonly known and prevalent odorous gas associated with domestic wastewater collection and treatment systems. It has a characteristic rotten egg odor, is extremely toxic, and is corrosive to metals such as iron, zinc, copper, lead and cadmium. Hydrogen sulfide is also a precursor to sulfuric acid formation, which corrodes lead-based paint, concrete, metals and other materials.

The conditions leading to H2S formation generally favor production of other malodorous organic compounds. Thus, solving H2S odor problems can often solve other odor problems as well. Many of the odors detected in wastewater collection and treatment systems result from sulfur-bearing compounds being present. 

origin of Sulfur in Domestic Wastewater

Sulfur is present in human and livestock excreta and sulfates are found in most water supplies. Sufficient sulfur is normally available in domestic wastewater in the form of organic sulfides such as mercaptans, and disulfides for the production of odorous gases by anaerobic and facultative bacteria.

The sulfate ion (SO42-) is one of the most universal anions occurring in rainfall, especially in air masses that have encountered metropolitan areas. Sulfate concentrations in wastewater can vary from only a few milligrams per liter (mg/L) to hundreds of milligrams per liter. Generally, for domestic wastewater, the main source of sulfide is sulfate.

Aluminium sulphate is also added to drinking water supplies in many areas to flocculate particulates. An interesting study in science recently linked this sulphate addition to drinking water to increased corrosion in sewer pipes http://www.aaas.org/news/science-replace-chemicals-not-pipes-save-worlds-crumbling-sewers due to H2S production.

The comment about alumninum sulfate from water treatment is important. Mustapha  can confirm which coagulant is used by local water treatment facilities.  While convention is to associate sulfurous odors with only hydrogen sulfide, in actuality a series of sulfurous compounds form that are oligomers of sulfide (e.g., di sulfide, trisulfide) and these are further methylated by bacteria to form methylated derivative. The dimethyl sulfides have lower odor thresholds and different sulfurous descriptors compared to hydrogen sulfide. Many researchers have shown that the volatile organic sulfur compounds (VOSCs) are the primary odorants in wastewater.

Sulphate in amounts of tens of mg/L can be added to groundwater through septic systems and unsewered sanitation. In areas where background concentrations of sulphate are naturally low, e.g. in reducing groundwaters where natural SO4 has been removed by reduction, sulphate can be used as a tracer for sewage.