Laboratory Simulation of Pentachlorophenol / Phenate Behaviour in an Alluvial Aquifer

Abstract

Abstract In 1978, about 18,000 litres of a chlorophenol/phenate solution leaked from a sawmill dip tank located approximately 120 metres from the Okanagan River in Penticton, B.C. Results of field studies indicated that the chlorophenol/phenate migrated through a surficial alluvial aquifer toward the river and that the retardation factor for the contaminants was between 1,05 and 1.43. A purge we 11 remedial operation recovered only about 40% of the spilled chlorophenol/phenate. More than five years after the purging operation, low levels of chlorophenol/phenate were still present in the groundwater. A column test to simulate the subsurface transport and purging behaviour of pentachlorophenol/phenate was conducted in the laboratory under conditions which duplicated, as closely as possible, those in the field. Results, which suggest a retardation factor of about 1.25 and non-equilibrium (i.e. slow) sorption/desorption, can account for the behaviour of the contaminants in the aquifer under natural flow conditions and during purging. The success achieved in the simulation indicates that these types of tests can be applied usefully in the study of contaminant behaviour in the subsurface. In addition, they could play an important role in waste site assessment and remediation programs where purging is an alternative. Data can be obtained at relatively low cost and at an early stage in an investigation, and could be employed to provide a preliminary assessment of the probable efficiency of purging. Moreover, the results could be applied to establish parameters and operating conditions that will improve the effectiveness of costly field tests that must precede the design of an optimal purging system.