Contaminants in groundwater can harm valuable drinking water and irrigation supplies and can damage aquatic environments in areas where contaminated groundwater discharges to surface water, but EOSi’s MicroC® premium carbon sources can be used to support biological treatment of groundwater contaminated with nitrogen, perchlorate, and selenium.
Biological treatment is often a more cost-effective way to remove contaminants from groundwater than physical or chemical treatment, with the added benefit of converting the contaminants into harmless compounds. In contrast, groundwater contamination is often remediated and/or hydraulically contained using an ex-situ “pump-and-treat” approach, in which the groundwater is pumped from wells, treated to remove the contaminants, and either reinjected into the aquifer or discharged to the surface.
Groundwater pump-and-treat may be a feasible treatment choice for contaminant plumes from point sources. Mining operations, chemical and fertilizer plants, petroleum refineries, and concentrated animal feeding operations (CAFOs) are potential point sources of contaminants. Pump-and-treat is generally not cost effective or feasible for treating widespread contamination from nonpoint sources, such as nitrate contamination of groundwater due to general agricultural activities.
How EOSi can help
EOSi’s services help remediation contractors design and implement MicroC® programs for groundwater treatment. Biologically treating nitrogen compounds may require nitrification in an aerobic reactor to oxidize ammonia and ammonium to nitrate and nitrite, followed by denitrification in an anoxic reactor to covert the nitrates and nitrites to nitrogen gas. Denitrifying bacteria will also degrade perchlorate, reducing it to chloride ions. When neither oxygen nor nitrate is present, microbes will use the forms of selenium typically found in water (selenate and selenite) as electron acceptors, producing elemental selenium that precipitates or is trapped in the biomass.
MicroC® helps establish and maintain the healthy biomass needed for removal of nitrogen, perchlorate, and selenium from groundwater. Unless the groundwater is also contaminated with organic compounds, there may not be enough biodegradable organics to support the biomass needed for nitrification in the aerobic zone. Denitrification and degradation of perchlorate and selenium in the anoxic zone occurs after the aerobic bacteria have already oxidized any biodegradable organic compounds. In both cases, the biomass will need a carbon source such as MicroC® that provides readily available food and energy. MicroC® can be custom blended to provide other essential microbial nutrients, such as phosphorus, that may not be present in sufficient quantities in the groundwater.