Selenium treatment of contaminated water by biological means involves the use of non-pathogenic bacteria, nutrients, project-specific media and electron donors, operated in an anoxic state. In selenium water treatment, selenite and selenate are reduced to insoluble selenium that is removed along with biomass and feed suspended solids by downstream liquid/solids separation. This process is effectively used for selenium removal from mining wastewater and other difficult industrial applications.
Alternatively, our high-efficiency ion exchange technology can be tailored to hard-to-treat waste streams containing selenium, offering high removal rates, cost efficiency, low waste rates and ease of operation with a small footprint.
Additionally, effective selenium water treatment may be accomplished using Envirogen’s Advanced Metals Removal System, which features Zero Valent Iron media.
The selenium dilemma
In the United States and Canada, the issue of selenium discharge (in its many forms) into the environment is becoming a matter of increasing concern. The U.S. Environmental Protection Agency has added selenium to its list of National Resource Water Quality criteria with a recommendation of 5 µg/L. Several states have followed with enforcement actions at this same low level. In Canada, an interim criterion of 1 µg/L has been established as a Canadian Water Quality Guideline, and 2 µg/L in British Columbia.
Envirogen Provides Selenium-Abatement Solutions
Envirogen Technologies offers a technology portfolio designed to respond to the selenium water treatment requirements created by mining, power generation, refining, agricultural and groundwater applications. Envirogen’s team works with consulting firms and directly with facility engineering teams to adapt these technologies to meet the needs of a specific selenium water treatment application. Envirogen’s resources can provide design, build, permitting and operating expertise as required. These initiatives will sustain guaranteed performance and cost-containment over the life of an installation.
Fluidized Bed Reactors
Best-in-class performance for high volume, high concentration clean-up
Envirogen’s patented fluidized bed reactor (FBR) biological treatment technology has been proven as a ‘best in class’ approach for handling large flow rates of selenium-containing wastewater, with low capital and operating costs, and over a wide range of influent and discharge limit conditions.
The FBR technology has a long track record of providing high removal rates with the low cost of operation and “green” benefits typical of biological treatment systems. The advantages of employing an FBR in a selenium water treatment application include an ‘order of magnitude’ cost advantage in system design and installation compared with other commercially available technologies. This is due to smaller system footprints as well as the ability to manage issues such as suspended solids and waste disposal in a far more effective manner over a broad range of influent flow rates.
The FBR works by utilizing project-specific media and electron donors, operated upflow in an anoxic state. Selenite and selenate are reduced to insoluble selenium that is removed along with biomass and feed suspended solids by downstream liquid/solids separation (usually filtration). This fluidized bed allows for very high biomass concentrations and consistent performance. The removal of excess suspended solids and biomass from the fluidized bed is accomplished with Envirogen’s patented biomass control and in-bed cleaning systems. Combining a high concentration of biomass with plug flow allows Envirogen FBR systems to achieve extremely low effluent selenium levels on a consistent basis.
Proven technology in coal mining applications
Envirogen’s FBR technology has demonstrated the ongoing ability to achieve <4.7 µg/Lselenium consistently for a 2800 GPM mining operation. Envirogen is an industry leader in the use of bioreactor technology, with over 200 systems installed in the United States.
Further reading on FBR in selenium applications:
Review of Available Technologies for the Removal of Selenium from Water ( prepared for the North American Metals Council)
Startup and Commissioning of a Full-Scale Selenium Treatment Facility For Mine Water Treatment
New Options for Treating Selenium in the Coal Industry
Advanced Metals Removal System (AMRS)
Envirogen Advanced Metals Removal System featuring Zero Valent Iron (ZVI) technology is another selenium water treatment option and can be utilized as the sole selenium removal treatment.
Zero Valent Iron media delivers high removal efficiencies allowing customers to comply with stringent wastewater discharge permit limits. A recent pilot study for treatment of coal ash pond water has demonstrated the effectiveness of the AMRS to reduce selenium levels to single digit parts per billion, even when faced with the more difficult-to-treat species such as selenate.
Envirogen has evaluated various iron based media for their ability to remove selenium and has the knowledge to recommend the best media for each individual application. Read more in our ZVI Media Evaluation Whitepaper.
High-Efficiency Ion Exchange
Ideal for lower concentrations & remote locations
Envirogen’s patented High Efficiency Ion Exchange technology offers treatment solutions that can be highly tailored to variable waste stream compositions and overall treatment system configurations.
Our High Efficiency Ion Exchange process is based on a patented system design that addresses many of the challenges seen in real world selenium removal applications. These systems are capable of removing selenium to very low levels (< 5 µg/L) – cost effectively. In addition, they have the advantages of a small footprint and automated operation, making them ideal for space restricted treatment facilities and remote locations.
Envirogen’s proprietary multi-bed system configurations offer faster kinetics and long media life while meeting a wide range of volume requirements. We employ remote monitoring and communication capability to enable our customers and field service technicians to ensure proper performance and attend the unit as needed.
Envirogen offers high-efficiency ion exchange systems with low capital investment options and pay-for-performance guarantees over the lifetime of the installation, creating the best opportunity for an optimized lifecycle cost.
Further Reading on Selenium Water Treatment
Envirogen is on the forefront of modeling biological system performance. Read more about our well received presentation at the EPRI Selenium Summit 2019 where Envirogen expert Paul Togna explained all the most recent research and learnings around selenium treatment and our groundbreaking predictive modeling. Envirogen Presents at EPRI Selenium Summit