Technologies to Remove Selenium from Water and Wastewater

After major pollution by nitrates and pesticides, soils and groundwater in some parts of the world are now facing the emergence of a third major issue of selenium (Se) contamination. Selenium occurrence in ecosystems results naturally from weathering of Se-containing rocks, and is further aggravated by human activities. Selenium is ubiquitous in the environment, and the two main sources of human exposure by Se are food and water. Se, a metalloid, is an important micronutrient due to Se antioxidant, anti-inflammatory and chemo-preventative properties. At normal dietary doses, selenium is an essential diet element that has nutritional properties and is necessary to maintain good health in humans and animals. Nonetheless, exposure to high concentrations of selenium is harmful to living beings. In terms of contamination, selenium as an emerging hazardous substance is receiving particular attention in developing countries, where research is focussing on water treatment. Actual remediation techniques are limited because removing Se from complex mixtures of substances is very challenging. Yet, techniques of water decontamination are developing rapidly. Here, we review selenium occurrence, pollution, properties and remediation. Advanced remediation include technologies based on zero-valent iron, iron-oxy-hydroxides, supported materials, nanofiltration, reverse osmosis, enhanced ultrafiltration, electrodialysis, and activated granular sludge.