Remediation of Nitrate in Drinking Water and Accumulation of Lipids using Microalgae

Abstract

The use of fertilizers in agriculture, and especially nitrogen to improve crop yield has resulted in the accumulation of high levels of nitrates in the groundwater (wells) throughout the mid‐western US states. This can lead to high levels of nitrates in drinking water, which exceeds the Safe Drinking Water Act, which the EPA limits at 10 mg/L. Drinking water containing nitrate levels above 10 mg/L is associated with significant health risks, particularly to unborn infants, as it can cause blue‐baby syndrome, a condition caused reduced capacity of hemoglobin to carry oxygen. Our laboratory has been employing microalgae to remediate nitrates to reduce this burden on water supplies. Two of the algal strains we have used were able to reduce Bold Basal Media (BBM) level nitrate (42mg/L) down to below 1 mg/L in 4 days, with an optical density (OD550) absorbance of around 3.0. In addition to remediating nitrate from contaminated sources, these microorganisms also accumulate lipids (triglycerides) under certain nutrient conditions and have been promoted as a feedstock for biofuels. Our lab has discovered several small compounds including WD30030 and WD20067 that induce lipid accumulation in algae without reducing growth and biomass in Chlamydomonas reinhardtii. In the present studies, we evaluated the impact of the compounds on several algal strains that have shown good growth in large bioreactors, Coccomyxia subellipsoidea – C169, Scenedesmus acutus f. alternans (UTEX B72), Chlorella kessleri (UTEX 2229) and Bumilleriopsis filiformis. Both nitrate removal and lipid accumulation during growth were monitored to assess whether or not these organisms can be used to couple nitrate remediation to production of high value lipid products.Support or Funding InformationNebraska Department of Economic Development and Vestal W2O, LLC