Evaluating Treatment and Options for Wastewater Treatment at Rest Areas and Truck Stations

Project summary:

The Minnesota Department of Transportation (MnDOT) is responsible for 52 safety rest areas (SFA) and truck stations (TS) across Minnesota served by subsurface sewage treatment systems (SSTS). Managing these SSTS is a critical activity of MnDOT, and a better understanding of the functionality and treatment of these systems is critical. The first project will continue field-based verification of groundwater mounding to estimate the influence of larger wastewater treatment systems on groundwater systems. The field data collected will be compared to commercially available mounding software estimates. This information will assist MnDOT in prioritizing upgrades.

Several studies will be conducted to better understand the treatment occurring in SSTS. The soil prior to and after septic system installation will be studied to understand the impacts of applying wastewater. A laboratory experiment will be conducted to determine the fate and transport of chemical of emerging concern (CEC) from wastewater in soil and vegetation. Two systems will be evaluated to determine if septic tank performance can be improved with the goal of increasing longevity, reducing blockages, and the frequency of maintenance.

MnDOT creates several related waste streams on which research is needed to better manage. Data will be collected on septage characteristics and recommendations provided on how to increase interest in the required maintenance on these systems from licensed pumpers and therefore increase competitive bidding. Flammable waste trap sand waste from TS will be evaluated to determine if less costly methods of disposal or reuse exist. In addition, reuse options for wash-down water from salt trucks will be explored to determine if more economical options could be employed to reduce the chloride contribution to wastewater treatment plants where this wastewater typically goes.

Each year of the project the University of Minnesota will serve as technical resource for MnDOT on upcoming projects.