PAHs and PFAS Stormwater Concentrations and Treatment at Seven Current and Recommissioned Military Facilities

The primary objective of the case study reported in this presentation, sponsored by SERDP (Strategic Environmental Research and Development Program) ER18-1371, was to evaluate the effectiveness of stormwater controls for reducing sediment recontamination in areas previously dredged. Composite stormwater samples were collected during a total of 23 storms at seven U.S. Department of Defense base locations having existing stormwater controls in the southwest, northwest, and arid southwest. The monitored influent, untreated, concentrations were generally similar to untreated stormwater quality found elsewhere. Paired influent and effluent stormwater concentrations were examined using several graphical and statistical tools for data grouped into sedimentation, media filter, and biofilter treatment categories.

The media filter removals of PFAS compounds were mixed, with most showing effluent concentration increases with only a few having moderate and low reductions, while biofilters had moderate to high removals of several PFAS compounds, with one (particulate PFOS) having increased effluent concentrations. Sedimentation resulted in many of the particulate and filtered PAH compounds having moderate to high concentration reductions, with several particulate PAHs having consistently low effluent concentrations. Media filters resulted in many moderate to high particulate and filtered PAH removals, but also with many increased effluent concentrations. Biofilters resulted in moderate removals of many filtered PAHs with several particulate PAHs having constant low effluent concentrations.

As expected, sedimentation was most effective for constituents mostly associated with larger particles. The biofilter installations were relatively large compared to their drainage areas, in contrast to the media filter installations. The resulting treatment flow rates and media contact times were therefore larger, resulting in generally increased performance for the biofilter systems. The most suitable treatment controls for a wide range of constituents of concern was found to be large biofilter systems, if space is available, and if groundwater can be protected.