Groundwater contains contaminants that pose environmental and health risks. Heavy metals precipitate in water at neutral and basic pH, but are soluble at a low pH. Hydrocarbons including kerosene and diesel have low specific gravities and float on the surface of groundwater. In contrast, halogenated hydrocarbons have high specific gravities and infiltrate water-bearing permeable rock known as aquifers. Pharmaceuticals including hormones, antibiotics and cosmetics enter groundwater via sewage treatment plants and waste deposits.
Groundwater is defined as water found underneath ground surfaces in soil pores and rock formations. An important water source, groundwater supplies 50% of drinking water in the United States, and 80% in Europe, according to an article in the Journal of Zhejiang University. Industrialization and agricultural production contaminate groundwater sources. Effective methods for groundwater purification are essential for ensuring a safe water supply.
Artificial Groundwater Recharge
Artificial groundwater recharge is a purification process using artificially installed sand and gravel layers which increases the quantity and quality of stored water by natural processes such as filtration, precipitation and sedimentation. This process is particularly conducted in sedimentary plains and river valleys and removes a range of inorganic and organic contaminants. The specific technique used depends on the availability of ground space and the level of purification required.
Phytoremediation uses genetically modified plants and bacteria to remove toxic contaminants from groundwater. Plants and bacteria are able to metabolize toxic compounds; however, naturally occurring plants and bacteria lack the enzymatic machinery to completely degrade compounds such as polychlorinated biphenyls (PCBs). Hence, since 2007, up to 300 million U.S. dollars have been invested annually in developing genetically altered organisms with this capability.
Iron possesses reductive and adsorptive properties, enabling it to remove groundwater contaminants. Iron with a 3+ valence state removes electrons from microbes during respiration. These oxidised microbes then remove electrons from metals such as chromium and uranium, precipitating them for easy uptake. Iron-based nanoparticles utilize the surface area, enhanced mobility and increased reactivity of nanoparticles to improve efficiency. Iron is also used in permeable reactive barriers (PRBs), which intercept and degrade contaminants in groundwater.
- "Science of the Total Environment"; Use of Iron-Based Technologies in Contaminated Land and Groundwater Remediation: A Review; Andrew Cundy, et al.; July 2008
- "Journal of Zhejiang University"; Natural Water Purification and Water Management by Artificial Groundwater Recharge; Klaus-Dieter Balke, et al.; January 2008
- "Journal of Zhejiang University"; Groundwater Protection: What Can We Learn From Germany? Yan Zhu, et al.; January 2008
- "Environmental Science Technology"; Phytoremediation of Polychlorinated Biphenyls: New Trends and Promises; Benoit Van Aken, et al.; April 2010
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