In-situ characterization of wastewater flow and transport from at-grade line sources to shallow groundwater

A better understanding of multidimensional unsaturated and saturated flow and transport under boundary conditions typical of on-site wastewater disposal systems is required to assess the risk to groundwater contamination. The main objective of this research is to characterize in-situ wastewater flow and transport from at-grade line sources on a shallow groundwater conditions. The research site was conducted at Wetaskiwin Rest Stop, Alberta, Canada, where ultraviolet disinfected wastewater has been disposed off to the ground via pressurized at-grade line sources since 2007. The site was characterized for wastewater plume and temporal groundwater fluctuation by using Electromagnetic induction (EM31) and (EM38); and by grid of 74 water table wells, 14 piezometers and 11 transducers. Groundwater was analyzed for selected tracers (pH, EC and Cl) and some microbiology (e.g. E. coli). From the results wastewater plume was identified; and wastewater plume center of mass and average flow direction were estimated. Along the horizontal plume center of mass, 30 monitoring wells in 10 nests and 31 temperature sensors in 5 nests were installed to get vertical resolution of the wastewater plume and to track contaminant transport over time. Results, implications and plans for future investigations will be presented. The research output will benefit future research on contaminant fate and transport and groundwater risk assessment plans. Key words: On-site wastewater treatment/disposal system, Wastewater plume, Groundwater contamination.