Nitrate contamination in water resources, human health risks and its remediation through adsorption: a focused review

The level of nitrate in water has been increasing considerably all around the world due to vast application of inorganic nitrogen fertiliser and animal manure. Because of nitrate's high solubility in water, human beings are getting exposed to it mainly through various routes including water, food etc. Various regulations have been set for nitrate (45-50 mgNO(3)(-)/L) in drinking water to protect health of the infants from the methemoglobinemia, birth defects, thyroid disease, risk of specific cancers, i.e. colorectal, breast and bladder cancer caused due to nitrate poisoning. Different methods like ion exchange, adsorption, biological denitrification etc. have the ability to eliminate the nitrate from the aqueous medium. However, adsorption process got preference over the other approaches because of its simple design and satisfactory results especially with surface modified adsorbents or with mineral-based adsorbents. Different types of adsorbents have been used for this purpose; however, adsorbents derived from the biomass wastes have great adsorption capacities for nitrate such as tea waste-based adsorbents (136.43 mg/g), carbon nanotube (142.86 mg/g), chitosan beads (104 mg/g) and cetyltrimethylammonium bromide modified rice husk (278 mg/g). Therefore, a thorough literature survey has been carried out to formulate this review paper to understand various sources of nitrate pollution, route of exposure to the human beings, ill effects along with discussing the key developments as well as the new advancements reported in procuring low-cost efficient adsorbents for water purification.

Automated summary

The level of nitrate in water is increasing worldwide due to the widespread use of inorganic nitrogen fertilisers and animal manure. Nitrate is highly soluble in water and humans are exposed to it through various routes, including water and food. Different methods, such as ion exchange and adsorption, can remove nitrate from water, but adsorption is preferred due to its simple design and satisfactory results with modified or mineral-based adsorbents. Adsorbents derived from biomass waste have high adsorption capacities for nitrate. This review paper provides a comprehensive survey of nitrate pollution sources, human exposure routes, health effects, and the development of low-cost efficient adsorbents for water purification.