The effectiveness of injected carbon sources in enhancing the denitrifying processes in groundwater with high nitrate concentrations

The single-well push-pull test (SWPPT) was adapted to quantify in denitrification rates and to assess microbial population dynamics in a highly nitrate-contaminated aquifer (105-311 NO3 mg L-1). In SWPPT through addition of fumarate as carbon source into test wells, significant NO3-consumtion was monitored in the well. The average zero- and first order rate coefficients were 7.85 and 0.82 mmol L-1 day(-1), respectively. Degradation rate of injected fumarate is 15.22 (zero-order) and 0.51 (first-order) mmol L-1 day(-1), respectively. Significant fumarate (electron donor, ED) and NO3(electron acceptor, EA) consumption, the production of dissolved CO2 during denitrification tests, and N2O production strongly indicate that the EAs consumption was mainly due to microbial activity. Therefore, SWPPT may be useful for quantifying in situ denitrification rates and for assessing microbial population dynamics in nitrate-contaminated aquifers in Silty Clay layer. (C) 2019 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.