This study examined several lines of evidence to determine effective strategies for the remediation of the nitrogen-contaminated groundwater surrounding a water treatment plant. Understanding the hydrogeology, chemistry and ecology and how they interact is essential to selecting an appropriate bioremediation strategy.
Design and methodology
To determine the most effective bioremediation strategy, statistical analysis was conducted on sampling data collected over >10 years in and around the water treatment plant. This allowed for further understanding of the hydrogeochemical site characteristics, to help inform the experimental phase. As a result, seven triplicate microcosms using the native groundwater ecosystem were established. The microcosms were used to test how inorganic electron donors at different concentrations affect the natural attenuation of nitrogen. Simultaneously, the effects of the different treatments on the microbial ecosystem were explored to determine any detrimental effects nitrogen plumes and the accompanying remediation efforts may have on the groundwater ecosystems.
Original data and results
Multivariate statistical analysis of sampling data showed that iron concentrations were significantly correlated with total N and NH4+ but not NO3- (P-values of 2.54*10-14, 1.65*10-4 and 0.283 respectively) and sulphur was significantly correlated with NH4+ but not total N and NO3- (P-values of 6.54*10-7, 0.18, 0.05627 respectively). These correlations are consistent with an important role for redox in the behaviour of N contamination in the groundwater.
The findings of the statistical analysis of the sampling data show correlations between iron and sulphur concentrations and total nitrogen, NH4+ and NO3- concentrations. By combining these data with microcosm experimental results, we hope to delineate how different concentrations of these ions affect the natural attenuation of nitrogen-contaminated groundwater. This in turn can be used to design bioremediation strategies based upon biostimulation of the native ecosystem.