sulfur and tellurium in Group VIA and between arsenic and bromine in Period 4. Selenium originated from the Greek word “Selene,” which means “moon.” It was discovered in 1817 by Jo¨ns Jacob Berzelius, “Father of Swedish Chemistry,” during the manufacturing of sulfuric acid, when he observed and analyzed a red deposit on the wall of lead chambers (Tinggi 2003). Selenium, mostly in combination with minerals that contain sulfur, is found in the Earth's crust. It generally exists in four oxidation stages, i.e. elemental selenium, selenites, and selenates. The oxidation states of the selenium found in nature are −2, 0, +4, or +6. Selenium is an essential micronutrient for its development and reproduction for humans, insects, fish, and many other species, but is known often to be toxic in amounts beyond the acceptable limits (Stadtman and TC 1978). Selenium's Acceptable Limit (AL) for groundwater is fixed at 0.01 mg/l (ppm) by the Bureau of Indian Standards (BIS). The spectrum of selenium consumption for optimum human and animal safety is very narrow, meaning that low selenium consumption is correlated with developmental defects and disease and a high amount of selenium contribute to toxicity (Reilly 2006; Kurokawa and Berry 2013). It is required for healthy joints, heart, and eyes. Its role in DNA synthesis, the immune system, and the reproductive system is of critical value. A well‐known example of selenium toxicity is Keshan disease in Hubei Province, China, where several deaths have been reported (Yang and Xia 1995; Kipp 2015). Selenium is primarily found in water as selenate (SeO42−) and selenite (SeO32−). Among the two compounds, selenate is the more stable and thus comparatively difficult to remove from water solutions. Different physiochemical qualities, including oxidation reduction, pH, their chemical types, and sorbing surfaces, regulate selenium in soils or irrigation waters (Mondal et al. 2004). While being widely used in the production of photocells, rectifiers, photocopy machines, paints, crystal glass, and pesticides, it is extremely hazardous if found in drinking water exceeding 10 μg/l where the extent of selenium use for industrial applications comprising electronics, photocopying machinery, glass, rubber, etc. varies from 1 to 7000 μg/l. Proclamation of selenium adulteration to the surroundings is frequently connected with copper casting accomplishments. Selenium can enter water supplies through interaction with selenium carrying minerals or through contact with polluted soil or from emancipation from excavations, earthen deposits, discharge from factories, or from agricultural overflow escaping natural selenium amalgams from desiccated, undeveloped terrestrial areas. Selenium (Se) compounds in groundwater have attracted the attention of scientists due to the increased contamination as result of increasing industrialization and activities like mining, combustion of coal, and use of selenium‐contaminated water for irrigation (Luoma and Presser 2009; Gibson et al. 2012). Selenium generally enters the food chain through both surface and underground waters which are used for irrigation and drinking purposes (Dhillon and Dhillon 2003; Zhang et al. 2014).
The objective of this chapter is to discover the noteworthy research going on in this domain using a scientometric approach and visualization tools. This study explores the most‐cited investigations, authors, institutions, and countries since 2000. It also presents insights about the leading technological developments in the removal of selenium.
This chapter systematically reviews high‐impact literature to identify, evaluate, and interpret the work of researchers, scholars, and practitioners so as to develop insights into various removal methods, such as sedimentation, filtration, activated carbon adsorption, ion exchange, reverse osmosis, and biological techniques for removing selenium from water and wastewater.
1.1.1 Contamination Status of Selenium
The authors have searched relevant literature related to the contamination status of selenium. Results indicate that selenium contamination is a global problem that affects a wide variety of human actions, from the most traditional farming methods to the most modern production processes. The USA, Canada, Republic of China, India, Japan, and Brazil are continuously making efforts to find out the technological solutions to remove the selenium.
In India, many areas are contaminated with selenium (Table 1.1). Punjab is the most affected region in Northwest India, with over 1000 ha of polluted fields. The main factors for the mobilization of Se and its bioavailability are alkaline soil pH, production of Se bioaccumulators, and inadequate industrial effluents/emissions treatment (Paikaray 2016). In the Majha belt of Punjab, which includes the Amritsar, Gurdaspur, and Tarn Taran districts, underground water is mainly contaminated with selenium and many other heavy metals (Virk 2018). Another belt which has groundwater quality‐affected habitations is the Doaba belt of Punjab, which includes the Jalandhar, Kapurthala, and Hoshiarpur districts (Virk 2019). As per Punjab Water Supply and Sanitation Department (PWSSD) data, selenium contamination of groundwater is greatest in the Jalandhar district in this belt. Selenium was detected in 105 habitations in Jalandhar, 30 in Kapurthala, and 19 in Nawanshahar. High‐level contamination of selenium was reported in the Malwa region of Ludhiana, with 90 habitations having higher than permissible limit of the metal with up to 0.140 mg/l content of selenium against the permissible limit of 0.01 mg/l. Another belt in Punjab, the “Malwa belt” of Ludhiana, Ferozepur, Roop Nagar, and Fatehgarh Sahib districts, also has selenium content in water sampled from tube wells (Virk 2019). The Doaba belt is the most selenium‐contaminated belt of Punjab. Also, in Punjab, surface soils are three to five times richer in selenium content compared to sub‐surface soils (Dhillon and Dhillon 1991).
Table 1.1 Selenium contamination status in Indian States.
| Author | Year | State | Districts | Contamination level |
|---|---|---|---|---|
| Virk | 2018 | Punjab (Majha Belt) | Tarn Taran | 0.010–0.076 |
| Gurdaspur | 0.010–0.094 | |||
| Amritsar | 0.010–0.039 | |||
| Virk | 2019 | Punjab (Doaba belt) | Jalandhar (Most contaminated) | 0.016–0.022 |
| Kapurthala | 0.01–0.082 | |||
| Hoshiarpur | 0.011–0.029 | |||
| Virk | 2019 | Punjab (Malwa belt) | Ludhiana | 0.016–0.14 |
| Roop Nagar | 0.01–0.20 | |||
| Ferozpur | 0.011–0.025 | |||
| Fatehgarh Sahib | 0.011–0.028 | |||
| Yadav et al. | 2005 | Rajasthan | Jaipur | Lower selenium level in Soil |
| Alwar | ||||
| Ghosh et al. | 2008 | Maharashtra | Mumbai |
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