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. 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.
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. 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.
How EOSi can help
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 supplemental 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.
EOSi’s services help remediation contractors design and implement MicroC® programs for groundwater treatment. We can perform bench scale treatability studies to select the appropriate MicroC® product and estimate the required feed rate. EOSi can conduct nutrient deficiency analyses and, if necessary, design a custom blend that is nutritionally complete. EOSi will monitor and refine the MicroC® program as needed as the remediation project proceeds through our Objective Based Programs such as ongoing technical and application support, remote process monitoring, troubleshooting and optimization programs to our MicroC® customers.