Iron in Stormwater FAQs
Iron is white, silvery metal that oxidizes quickly when encountering water and oxygen. Dissolved iron as ferrous iron (Fe2+), ferric iron (Fe3+) and particulate iron, are forms commonly found in stormwater. Naturally present in groundwater, iron in these forms can make its way into the environment through stormwater in contact with groundwater and surface water.[xi] For example, drainage from abandoned mines can deliver toxic levels of iron into rivers and streams.[xii] Elevated levels of iron in stormwater can be caused by rusting steel in constant contact with standing water.
Iron ore (image courtesy of Wikipedia)
Iron should be removed from stormwater because excessive amounts in drinking water and the environment can cause harm to human health and wildlife habitat. Although iron is an essential mineral, diseases of aging such as Alzheimer’s disease, other neurodegenerative diseases, arteriosclerosis, diabetes mellitus, and others have been linked to excess iron intake.[i] High concentrations of iron in drinking water can produce an unpleasant taste and stain home fixtures.[ii]
While iron in in trace amounts is an essential dietary mineral for fish and other animals as it is for humans, iron toxicity has been observed in certain fish species at concentrations in excess of 1,380 mg iron/kg in their diet.[iii]
Indirectly, iron can kill fish by causing algae blooms, which create biological oxygen demand[iv], smother aquatic plants and produce potent neurotoxins.[v] Even low concentrations of iron (0.1-1.0 mg/L) may cause nuisance algae species to replace inoffensive species[vi], adversely affecting fish habitats.
Because iron in stormwater primarily exists in solid, particulate form, passive media filtration and polishing can be used to effectively remove particulate iron from stormwater prior to discharge to help facilities meet benchmarks or NALs. The Aquip passive media filter offers an enhanced level of iron removal from stormwater. Learn more about our stormwater media filtration technologies.