Life-cycle case study comparison of permeable reactive barrier versus pump-and-treat remediation.

A permeable reactive barrier (PRB) is a passive remediation technology, which over decades of use, may reduce lifetime environmental impacts when compared with a conventional pump-and-treat system (PTS). Greater material production requirements to install PRBs may offset the expected reductions in operational phase impacts and the trade-offs can be investigated in a life-cycle assessment (LCA). The life-cycle environmental impacts of a zerovalent iron (ZVI) containing PRB with a funnel and gate configuration and a PTS were compared in a case study. Potential impacts of the model PRB are driven by the ZVI reactive medium and the energy usage during construction, while for the PTS they are driven by the operational energy demand. Medium longevity governed the magnitude of the potential PRB impacts and the extent to which it was optimal relative to the PTS. Even at conservatively low estimates of longevity, the PRB offers significant environmental advantages in impact categories of human health and ozone depletion. The minimum ZVI longevity for PRB benefit over the PTS system in all impact categories was 10 years. Suggested PRB design innovations to reduce environmental impacts include the development of alternative reactive media and construction methods.