title: Selenium: environmental significance, pollution, and biological treatment technologies.
abstract: Selenium is an essential trace element needed for all living organisms. Despite its essentiality, selenium is a potential toxic element to natural ecosystems due to its bioaccumulation potential. Though selenium is found naturally in the earth's crust, especially in carbonate rocks and volcanic and sedimentary soils, about 40% of the selenium emissions to atmospheric and aquatic environments are caused by various industrial activities such as mining-related operations. In recent years, advances in water quality and pollution monitoring have shown that selenium is a contaminant of potential environmental concern. This has practical implications on industry to achieve the stringent selenium regulatory discharge limit of 5μgSeL(-1) for selenium containing wastewaters set by the United States Environmental Protection Agency. Over the last few decades, various technologies have been developed for the treatment of selenium-containing wastewaters. Biological selenium reduction has emerged as the leading technology for removing selenium from wastewaters since it offers a cheaper alternative compared to physico-chemical treatments and is suitable for treating dilute and variable selenium-laden wastewaters. Moreover, biological treatment has the advantage of forming elemental selenium nanospheres which exhibit unique optical and spectral properties for various industrial applications, i.e. medical, electrical, and manufacturing processes. However, despite the advances in biotechnology employing selenium reduction, there are still several challenges, particularly in achieving stringent discharge limits, the long-term stability of biogenic selenium and predicting the fate of bioreduced selenium in the environment. This review highlights the significance of selenium in the environment, health, and industry and biotechnological advances made in the treatment of selenium contaminated wastewaters. The challenges and future perspectives are overviewed considering recent biotechnological advances in the management of these selenium-laden wastewaters.
authors.affiliation: UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands. Electronic address: lea_chua_tan@yahoo.com.
authors.forename: Lea Chua
authors.initials: LC
authors.lastname: Tan
authors.affiliation: Biofouling and Biofilm Process Section, Water and Steam Chemistry Division, Bhabha Atomic Research Centre Kalpakkam, 603102 Tamil Nadu, India. Electronic address: venkatany@gmail.com.
authors.forename: Yarlagadda V
authors.initials: YV
authors.lastname: Nancharaiah
authors.affiliation: Université Paris-Est, Laboratoire Géomatériaux et Environnement (EA 4508), UPEM, 77454 Marne-la-Vallée, France. Electronic address: Eric.vanHullebusch@u-pem.fr.
authors.forename: Eric D
authors.initials: ED
authors.lastname: van Hullebusch
authors.affiliation: UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands; Department of Chemistry and Bioengineering, Tampere University of Technology, P.O-Box 541, Tampere, Finland. Electronic address: p.lens@unesco-ihe.org.
authors.forename: Piet N L
authors.initials: PNL
authors.lastname: Lens
mesh_terms: D001673:Biodegradation, Environmental; D019149:Bioreactors; D001709:Biotechnology; D012643:Selenium; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D012643:Selenium; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Bioreactors; Bioremediation; Selenium bioreduction; Selenium environmental impact; Selenium nanoparticles; Selenium pollution; Selenium recovery; Selenium wastewaters