Real-Time Monitoring of Selenium Species in Power Plant Wastewaters via Optical Spectroscopy
Energy Research Company (ERCo) and Lehigh University are developing a new rapid sensor for measuring trace amounts of selenium in coal-fired power plant wastewater streams down to the single parts-per-billion (ppb) level. With EPA regulations pending on releases of selenium in wastewaters from power plants, plant operators are finding that commercially available technology is not suitable for ensuring compliance with the new regulations. These regulations require monitoring selenium at the single ppb level. There are several important advantages of our instrument as compared to other potential methods such as ICP-MS or ICP-OES. First, the method is rapid, allowing for analyses within minutes. Second, the method is amenable to automation, so dedicated lab personnel are not required. Third, the apparatus is compact and comprised of off-the-shelf components that are inexpensive compared to other laboratory instruments. Fourth, our instrument is designed to be used in the field and will collect data from any water source in near real time. Fifth, maintenance is minimal and finally, the cost is quite low. Furthermore, selective concentration of different ionization states of selenium was also demonstrated. Selenium is present in wastewaters in two main ionization states, +4 and +6. The fraction of each ionization state is important to know because it affects selenium treatment technologies. We were able to measure each one with a single instrument. The Phase II work plan will automate our instrument and expand the measurements to other heavy metals such as mercury and arsenic, the two other heavy metals covered in the new EPA regulations. We will also field test the instrument at an operating coal fired power plant.