Stormwater biofilters are being implemented widely in urban environments to provide green space, alleviate flooding, and improve stormwater quality. However, biofilters with conventional media (sand, soil, and/or mulch or compost) do not reliably remove contaminants from stormwater. Research suggests addition of biochar to the biofilter media can improve the pollutant removal capacity of biofilters. In the current work, we present a systematic review of laboratory and mesocosm studies of biochar-augmented biofilters and an assessment of watershed-scale implementation of biofilters on local water quality. A full text review of 84 papers was conducted; of these, data were extracted from the 14 that met our inclusion criteria. log10 removal of microbial pollutants and trace organic contaminants (TOrCs) by biochar-augmented media is generally greater than those of the controls containing just sand, soil, and/or compost. log10 removal of nitrogen, phosphorous, total organic carbon, and total suspended solids in biochar-augmented biofilters is not clearly higher than those of control experiments. A supplemental analysis of four studies reporting longer-term breakthrough data revealed that TOrC removal effectiveness varies substantially among high temperature wood-based biochars, and that operational lifetimes of full-scale systems constrained by TOrC sorption capacity could range from five months to over seven years depending on the selected biochar. At the watershed-scale, biochar-augmented biofilters can provide enhanced treatment of runoff, resulting in the need for fewer treatment units or a smaller volume of watershed runoff treated to meet water quality criteria compared to their conventional counterparts. While their installation can reduce the load of pollutants to receiving waters, achieving concentration-based water quality targets may prove difficult even when pollutant removal capacity is high. This work highlights the importance of a systems approach to studying how biofilter installation affects water quality within a watershed. We identify several topical areas where further research is needed, especially as installation of biofilters and other stormwater control measures gain popularity in highly urbanized watersheds.
|Original language||English (US)|
|Number of pages||18|
|Journal||Environmental Science: Water Research and Technology|
|State||Published - Jun 2020|
Bibliographical noteFunding Information:
This work received funding from NSF through grant number EEC-1028968, NSF = US National Science Foundation (www. nsf.gov). The sponsor played no role in the study design, data collection and analysis, decision to publish or prep of the manuscript. This work was also partially supported under Assistance Agreement No. R836174 awarded by the U.S. EPA to the Colorado School of Mines, the Nature Conservancy, and the University of California-Berkeley. It has not been formally reviewed by EPA. The views expressed in this document are solely those of the authors and do not necessarily reflect those of the agency. EPA does not endorse any products or commercial services mentioned in this publication.
© 2020 The Royal Society of Chemistry.