Pilot-scale evaluation of a permeable reactive barrier with compost and brown coal to treat groundwater contaminated with trichloroethylene

Abstract

This study evaluates, under field conditions, the efficiency of a permeable reactive barrier (PRB) with compost and brown coal to remove trichloroethylene (TCE) (109 μg/L) from contaminated groundwater. Three stainless steel boxes (1.2 × 0.5 × 0.5 m) with the brown coal-compost mixture at three different mixing ratios of 1:1, 1:3, and 1:5 (by volume) were installed to simulate the PRB. Groundwater from the TCE-contaminated aquifer was pumped into the system at a flow rate of 3.6 L/h. Residence times in the boxes were of: 25, 20, 10 h, respectively. Effluent samples were analyzed for TCE and its daughter products: dichloroethylene (DCE), vinyl chloride (VC) and ethane. During the 198-day experimental period TCE concentrations in groundwater decreased below ≤1.1 μg/L, i.e., much lower than groundwater and drinking water standards in Poland. After 16 days cis-1,2-DCE was monitored indicating possible reductive dechlorination of TCE. However, complete transformation of TCE into non-toxic byproducts was not evidenced during the time of experiments, indicating that reductive dechlorination slowed down or stopped at DCE, and that the designed residence times were not long enough to allow the complete dechlorination process.