Meeting the criteria: linking biofilter design to fecal indicator bacteria removal

The capture, treatment, and reuse of storm-water runoff are win-win propositions that can lead to improvements in both human water security and ecosystem health. Although not all treatment technologies facilitate the capture, treatment, and reuse of water, biofilters do. Biofilters are engineered analogues of natural systems that use low energy, natural processes to treat stormwater. Biofilter design is closely linked to treatment efficiency. As such, specific design components, such as submerged zones (SZs: saturated, organic-rich layers near the base of biofilters), can significantly affect contaminant removal. Of particular interest, is the utility of SZ biofilter designs for removing indicators of pathogens, the so-called fecal indicator bacteria (FIB). FIB exist at high concentrations in stormwater, sometimes several orders of magnitude above recreational, nonpotable reuse, or drinking water standards, and have been identified as one of the primary barriers to stormwater reuse. A comparison of FIB removal values from literature indicates that SZ systems significantly enhance FIB removal (similar to 10-fold) relative to other design configurations (p<0.05). Processes that may contribute to this effect include physicochemical filtration, biofilm formation, and protistan grazing, amongst others. A high degree of synergy exists between processes, and many unknowns remain. Model frameworks developed for evaluation of similarly synergistic systems, including biofilter analogues like the vadose zone, may be useful for addressing these unknowns and informing future biofilter design. (C) 2015 Wiley Periodicals, Inc.