Iron
Chemical symbol/abbreviations:
Fe, Fe2+, Fe3+
Forms commonly found in stormwater:
Dissolved iron as Fe2+ (ferrous iron) and Fe3+ (ferric iron), particulate iron
Adverse human impacts:
Adverse impacts on the environment:
Even low concentrations of iron (0.1-1.0 mg/L) may cause nuisance algae species to replace inoffensive species[vi]
Background:
Iron is a white silvery metal that oxidizes quickly when coming into contact with water and oxygen. It is the fourth most abundant element in the earth’s crust, making up about 5% of its mass. It is soft, malleable, and strongly magnetic. Within humans and all other animals, iron plays a crucial role of carrying oxygen within the blood in the form of hemoglobin.1
Pure iron is not often used to manufacture products. Iron is much stronger and more useful when alloyed with carbon. Wrought iron and steel are examples of such iron alloys with carbon contents of 0.2 – 1.5%.[viii] Due to its abundance and mechanical strength, iron in the form of steel is used as a common building material for anything from bicycles to bridges.
| Freshwater – Aquatic Organisms (Total Recoverable; pH 6.5-9.0) | Saltwater– Aquatic Organisms | Human Health for the consumption of | |||
|---|---|---|---|---|---|
| Acute (µg/L) | Chronic (µg/L) | Acute (µg/L) | Chronic (µg/L) | Water + Organism (µg/L) | Organism Only (µg/L) |
| na | 1000 | na | na | 300 | na |
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.
Stormwater Treatment to Remove Iron
The Aquip® industrial stormwater filtration system uses an innovative enhanced media filtration process to effectively remove soluble and insoluble aluminum and other metals as well as oils, suspended solids, organics and nutrients from industrial stormwater runoff.
The Purus® Stormwater Polishing System provides the most advanced level of stormwater treatment and is designed for challenging stormwater conditions or targeted pollutant removal.
Footnotes
[i] George Brewer, Risks of Copper and Iron Toxicity during Aging in Humans 23 Chem. Res. Toxicol. 2, 319–326 (Dec. 2009).
[ii] Illinois Dept. Public Health, Iron in Drinking Water (1999) http://www.idph.state.il.us/envhealth/factsheets/ironFS.htm (last visited July 25, 2019).
[iii] National Research Council Subcommittee on Fish Nutrition, Nutrient Requirements of Fish 19 (1993) available at http://www.nap.edu/openbook.php?record_id=2115&page=19 (last visited July 25, 2019).
[iv] Florida Dept. of Environmental Protection, EcoSummary BioRecon Report, Camp Five Branch below Camp Five Landfill, Escambia County (Mar. 21, 2002) available at http://publicfiles.dep.state.fl.us/DWRM/eco/Camp%205%20Landfill%20Branch.pdf (last visited July 25, 2019).
[v] Queensland Univ. of Tech., Is Iron from Soil a Factor in Algae Blooms? ScienceDaily, Feb. 4, 2010, http://www.sciencedaily.com/releases/2010/01/100128101855.htm; Brandon Keim, Climate Quick Fix Could Create Toxic Algae Blooms, WIRED, Mar. 16, 2010, http://www.wired.com/wiredscience/2010/03/neurotoxic-geoengineering/ (last visited July 25, 2019).
[vi] Stephen Morton & Terrence Lee, Algal Blooms – Possible Effects of Iron 8 Environ. Sci. Technol. 7, 673 (1974) available at http://pubs.acs.org/doi/abs/10.1021/es60092a005 (July 25, 2019).
[vii] U.S. EPA, National Recommended Water Quality Criteria, https://www.epa.gov/environmental-topics/water-topics (last visited July 26, 2019).
[viii] HyperPhysics, Iron http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/fe.html#c3 (last visited July 26, 2019).
[ix] U.S. Geological Survey, Minerals Commodity Summaries-Iron Ore (2019) available at http://minerals.usgs.gov/minerals/pubs/commodity/iron_ore/feoremcs05.pdf (last visited July 25, 2019)
[x] U.S. Geological Survey, Minerals Commodity Summaries-Iron Ore (2019) available at http://minerals.usgs.gov/minerals/pubs/commodity/iron_ore/feoremcs05.pdf (last visited July 25, 2019).
[xi] The Earth’s Ferrous Wheel, The Nature Education Knowledge Project https://www.nature.com/scitable/knowledge/library/earth-s-ferrous-wheel-15180940 (last visited July 26, 2019).
[xii] U.S. Geological Survey, Water, How does mine drainage occur? https://www.usgs.gov/faqs/how-does-mine-drainage-occur?qt-news_science_products=0#qt-news_science_products (last visited July 26, 2019).