Case Study: Selenium

Selenium compounds can be removed from water by physical, chemical, or biological processes. Some of these methods, however, can be cost prohibitive and are not always successful at meeting discharge limits. BRT’s successful method of removing selenium from water is “biological transformation”. This involves changing the soluable oxide forms of selenium (selenate and selenite) to the elemental form, which is non-soluble in water, and as a result causes selenium to precipitate out of solution to meet discharge limits. Microbiological methods of selenium detoxification have been documented to be both successful and cost-effective

In anaerobic environments (those devoid of oxygen), bacteria have evolved respiratory mechanisms which utilize compounds other than oxygen to generate energy. Certain bacteria have been found that can breathe using selenate and selenite as a terminal electron acceptor instead of oxygen.

As part of their metabolism, and in the presence of our proprietary nutrients and substrate, the bacteria will then reduce selenate and selenite to elemental selenium. Therefore, as a result of the activity of selenate-respiring bacteria, selenate and selenite are converted from water-soluble compounds into non-soluble elemental selenium which precipitates out of the water.

selenium_molecules

 

 

 

 

 

BRT has demonstrated enhanced in situ bioremediation. The treatment technology utilizes a combination of carbon substrate and nutrient injections in tandem with application of a selenate-degrading bacterial culture. This treatment process has significantly reduced total selenium concentrations in the discharge waters by 91% in just 13 days. The technology has proven to be an efficient and cost effective method of removing selenium from surface water discharges. BRT’s process requires no electricity, produces no sludge and allows discharge limits to be obtained, even in winter months.

Selenium_graph2

Date: April 9, 2013
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