N-P Fertilization Stimulates Anaerobic Selenium Reduction in an End-Pit Lake

Area of Science:

• Environmental Science
• Microbiology
• Ecotoxicology

Background:

• Selenium (Se) is an essential micronutrient but toxic to aquatic life at elevated concentrations.
• Watersheds with selenium-rich sources necessitate extensive, long-term treatments to reduce toxicity.
• Previous small-scale successes in selenium mitigation using anaerobic bacterial bioreactors.

Purpose of the Study:

• To apply anaerobic bacterial bioreactor principles to a large-scale end-pit lake ecosystem for selenium mitigation.
• To investigate the feasibility of enhancing anaerobic microbial habitats for selenium reduction in a whole lake.
• To develop an effective and inexpensive method for treating large volumes of selenium-contaminated water.

Main Methods:

• Application of anaerobic bacterial bioreactor principles to an end-pit lake ecosystem.
• Fertilization of the lake with nitrogen (N) and phosphorus (P) to stimulate primary production.
• Creation of a meromictic, anoxic layer to foster anaerobic, selenium-reducing bacteria.

Main Results:

• Increased primary production and establishment of an anoxic layer within the lake.
• Enhanced habitat for naturally occurring anaerobic selenium and sulfur-reducing bacteria.
• Tenfold reduction in selenium concentrations within two years, achieving water-quality guideline values.

Conclusions:

• Successful demonstration of a novel, large-scale treatment for selenium-contaminated water bodies.
• Inexpensive and effective method for mitigating a persistent global aquatic pollutant.
• Ecological engineering approach can be used to enhance natural processes for bioremediation.