Selenium is present in its aqueous form as selenate (Se6+) and selenite (Se4+) ions in mining and power plant wastewater. These ions are difficult to treat and remove as they exist in dissolved state. To remove selenium, precipitation is one of the common methods used, which requires a large quantity of chemicals and results in high sludge production and high disposal and chemical costs. One of the benefits of biological treatment is that it avoids addition of large quantity of chemicals. Both selenate (Se6+) and selenite (Se4+) species are reduced to elemental selenium by biological anoxic reaction. Selenium in particulate form is removed by a follow-up solid-liquid separation step.
Certain states in North America and around the world strictly regulate selenium in the treated effluent before their discharge to a water body. Such challenges can be met by the specially designed Anoxic MBBR-based ActiveCell™ selenium removal technology offered by Headworks Bio.