Coal contains a number of heavy metals that when combusted can end up in the fly and bottom ash as well as the wastewater streams from coal-fired power plants. Common elements of concern include mercury, arsenic, chromium, sulfur, boron, and many others. One of the most challenging elements to treat in the wastewater or nearby waterways is selenium. Elevated concentrations of selenium are often seen in certain types of coal, particularly from sources that are high in sulfur, and can be problematic when trying to meet the impending EPA effluent limitation guidelines (ELG) and coal combustion residuals (CCR) regulations.
Efficient selenium treatment and understanding ecological risks associated with the contaminant requires detailed molecular information to make educated decisions. As with any element, the molecular form of selenium, or chemical species, dictates its interaction with the environment and uptake into organisms.
More than a dozen selenium species have been identified in both natural and anthropogenically-impacted waters, including volatile forms like dimethylselenide and reduced forms like selenocyanate. As analytical technology has advanced, more information regarding the complexity of selenium chemistry is available. This is especially important in situations where biological activity can produce complex organic selenium species, as found in natural environments as well as biological treatment systems. Regulatory agencies in North America and other parts of the world are increasing their understanding regarding the implications of the different molecular forms of selenium and have already begun to implement regulations based upon not only discrete limits, but the uptake, or bioaccumulation rates, of the various selenium species in the surrounding ecosystem.
Our typical chromatogram for Selenium Speciation by IC-ICP-MS:
Brooks Applied Labs offers highly advanced analytical services for the determination of selenium species with our customized methods coupling an array of chromatographic systems with inductively coupled plasma – mass spectrometry (ICP-MS), employing interference removal technologies (DRC, CRC, and QQQ). Using these methods, Brooks Applied Labs supports the identification and quantitation of numerous selenium species, including the following: selenite, selenate, selenocyanate, methylselenocysteine, selenomethionine, dimethylselenide, dimethyldiselenide, selenosulfate, methylseleninic acid, dimethylselenoxide, selenomethionine oxide, and selenoproteins.
Standard regulatory practices limit the total concentration of toxic metals, such as mercury, when discharged from industrial sources, ignoring the importance of speciation and bioavailability. This can result in dischargers spending more on wastewater treatment than...