Arsenic is a naturally occurring element found in groundwater sources around the world. Human exposure to arsenic can cause short and long-term health effects. In order to protect consumers from drinking water contaminated with arsenic, regulatory standards limiting the amount of arsenic have put into effect.
Chromium species, including hexavalent chromium (Chromium-6), can occur naturally in groundwater at relatively low levels from chromium containing geologic formations. Additionally, there are demonstrated instances of Chromium-6 being released into the environment from leakage, poor storage or inadequate industrial waste disposal practices.
Chlorination is the most widely used water disinfection process with great success in the drinking water industry for over a century. Unfortunately, chlorine reacts with organic matter present in water and results in the formation of toxic halogenated disinfection by-products (DBPs), including trihalomethanes (THMs).
Selenium is naturally occurring trace element and essential nutrient to humans at low exposure levels. However, aqueous forms of selenium at low exposure levels of > 5 ppb, while a health benefit for humans, can pose major risks to aquatic and terrestrial wildlife. Studies have linked elevated selenium levels as the cause of reproductive issues in fish and birds resulting from the bioaccumulation of the substance within animal tissue. Mining, combustion of coal for thermoelectric power production, agricultural and other practices have led to selenium pollution of global water resources. The negative effect of selenium on aquatic wildlife has led to increased regulatory pressure to reduce levels of this trace element.