A two-dimensional numerical solute transport model was developed for simulating an enhanced in situ denitrification experiment performed in a nitrate-contaminated aquifer on Cape Cod, Massachusetts. In this experiment, formate (HCOO-) was injected for a period of 26 days into the carbon-limited aquifer to stimulate denitrification. Calibration of the vertical-profile site model was demonstrated through error analysis and comparison with formate, nitrate, and nitrite concentration data monitored along a transect of three multilevel groundwater sampling wells for 75 days after initial injection. Formate utilization rates were approximately 142 and 38 ??M/day for nitrate and nitrite reduction, respectively. Nitrate and nitrite utilization rates were approximately 29 and 8 ??M/day, respectively. Nitrate utilization rates under enhanced conditions were 1 order of magnitude greater than previously reported naturally occurring rates. The nitrite production rate was approximately 29 ??M/day. Persistence of nitrite was attributed to a combination of factors, including electron donor (formate) limitation late in the experiment, preferential utilization of nitrate as an electron acceptor, and greater nitrite production relative to nitrite utilization.
Additional Publication Details
Modeling enhanced in situ denitrification in groundwater