A review on environmental selenium issues

Abstract

Selenium is an essential element since it is necessary for metabolism and is also toxic to the living things if it is consumed above the desirable limit. For instance, up to 40 µg per d of dietary selenium is essential for human health; however, consumption of a little over 400 µg per d could result in adverse physiological problems. In the environment, selenium occurs in different species; of which selenate and selenite are its most toxic forms accounting for 95% of selenium toxicity. Though, selenium fortification is important for normal human physiology in selenium deficient environments, it needs to be minimized or removed from selenium rich environmental media. Thus, its quantification is significantly important to control per limit. Currently there is advancement in the detection and quantification of selenium in environmental including the use of a Hydride Generating Atomic Absorption Spectroscopy. Due to the excess occurrences of selenium in different locations the removal techniques from geogenic or anthropogenic sources include microbial metabolism, phytoremediation, sorption, membrane separation, coagulation, ion exchange and catalytic reduction. Most of all, the microbial removal is applied in drinking water supply and in selenium recovery from wastewater sludge. Though current selenium removal from sorption studies reported better efficiency, phytoremediation appears attractive due to its field scale application advantage. However, the fate of selenium following phytoremediation remains unaddressed.