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 - jack.adams@utah.edu

 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