Investigating the redox sensitivity of para-toluenesulfonamide (p-TSA) in groundwater

The groundwater downstream of a former sewage irrigation farm in Berlin is contaminated with ammonium (NH4 (+)) and para-toluenesulfonamide (p-TSA), besides other anthropogenic pollutants. In the field, in situ removal of NH4 (+) by gaseous oxygen (O-2) and air injection is currently being tested. A laboratory column experiment using aquifer material and groundwater from the site was performed to determine whether this remediation technology is also feasible to reduce high p-TSA concentrations in the anoxic groundwater. First, the column was operated under anoxic conditions. Later, compressed air was introduced into the system to simulate oxic conditions. Samples were collected from the column outlet before and after the addition of compressed air. The experiment revealed that whereas p-TSA was not removed under anoxic conditions, it was almost fully eliminated under oxic conditions. Results were modelled using a transient one-dimensional solute transport model. The degradation rate constants for p-TSA increased from 2.8E-06 to 7.5E-05 s(-1) as a result of microbial adaption to the change of redox conditions. Results show that O-2 injection into an anoxic aquifer is a successful strategy for p-TSA remediation.