Bioremediation of Chlorate and Chromium Contamination with Native Microbial Culture in Cold Climate

Chlorate and hexavalent chromium are two chemicals with adverse health effects that may cause groundwater contamination in industrial areas. The objective of this study was to determine if the native microorganisms collected from a site contaminated with chlorate and chromate can lower the concentration of these chemicals in groundwater to acceptable regulatory levels. Several anaerobic microcosm experiments were conducted with synthetic groundwater (media), native microorganisms, acetate as an electron donor, nitrogen, phosphorus, and minerals. The microorganisms utilized 2200 mg/L acetate to remove 1000 mg/L of chlorate and 3 mg/L of hexavalent chromium entirely from the media provided that the groundwater is supplemented with additional nitrogen and phosphorous (with the Carbon:Nitrogen:Phosphorous molar ratio of 100:10:5). The added trace minerals solution prepared based on American Type Culture Collection (ATCC) 1191 medium did not improve the remediation process. Native microbial culture derived from the contaminated site removed the chlorate and chromate from the synthetic groundwater at 20 °C in about 40 days. The same removal was achieved at 10 °C, but in a longer timespan of 80 days. This work confirmed the importance of ensuring the presence of sufficient N and P to stimulate chlorate- and chromate-reducing bacteria in the groundwaters.