PROBLEM OVERVIEW This site is an open pit coal mining operation, where water flowing through waste rock requires treatment for
selenium and nitrate. Coal mining waters are often a difficult target for conventional metal and inorganic
treatments. Various metal species, including selenium, leach out from the waste rock, when exposed to
rainwater. In addition, nitrates enter the mine runoff from nitrogen-containing blasting compounds. A
combination of moderate to high nitrate and selenium levels is a common problem in many coal mines across
North America. Presence of nitrates is problematic, as they are a preferred electron acceptor to selenate and
selenite. Sufficient and stable electron provision is necessary to achieve both nitrate and selenium reduction.
ELECTRO-BIOCHEMICAL REACTOR TECHNOLOGY
All biological and chemical metal and inorganic reduction/removal methods are based on redox reactions.
Electrons are needed for contaminant transformations, and conventional treatments rely on chemicals and
nutrients to provide these electrons. The Electro-Biochemical Reactor (EBR) technology reduces the amount
of chemical needed by directly supplying excess electrons to the reactor and microbes, using a low applied
voltage. 1 to 3 volts is all that is required, (1-volt supplies approximately 1 trillion, trillion electrons). These
electrons replace the electrons normally supplied by excess nutrients and chemicals, at a considerable
savings. The provided electrons make reactors more controllable, economical, and robust than past
generations of biological treatment systems. Moreover, they provide readily available electrons for microbial
growth and contaminant removal, resulting in better performance in less time and space and with greater
efficiency. Using selenium as an example, in the EBR biological treatment system, the selenium oxidation state
is not as crucial as it is in other treatment processes. Selenate is reduced to selenite, which in turn is reduced
to elemental selenium, which is virtually insoluble.
The pilot system is completely contained and designed for flow rates of 0.5 to 3 LPM, and PLC-controlled.
The EBR technology, while using only slightly modified standard treatment equipment, improves conventional
biological treatment process resulting in about 25% savings in capital costs and up to 50% savings in
operational costs.
RESULTS
The EBR pilot system removed selenium and nitrate-N to below
discharge criteria. Selenium was removed from influent values
averaging 105 µg/L to an average 0.3 µg/L in the system effluent.
Selenium discharge goal (10 µg/L) was met within the first 4 hours
of the EBR treatment. Nitrate-N was present in the wastewater at an
average concentration of 50 mg/L and was reduced to below
0.1 mg/L in the system effluent, exceeding the discharge goal of
3 mg/L.
Influent temperature varied between 2-16oC and had little to no
effect on EBR performance.
CONTACT INOTEC
www.inotec.us
Jack Adams, Ph.D.
President and CTO
INOTEC
(801) 712‐2760 - [email protected]
EBR technology starts with the best aspects of proven microbial and chemical systems and
takes them to the next level of performance and cost-effectiveness