Biochar-augmented biofilters to improve pollutant removal from stormwater - can they improve receiving water quality?

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 suggest...

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Bibliographic Details
Published in:Environmental science water research & technology 2020-06, Vol.6 (6), p.152-1537
Main Authors: Boehm, Alexandria B, Bell, Colin D, Fitzgerald, Nicole J. M, Gallo, Elizabeth, Higgins, Christopher P, Hogue, Terri S, Luthy, Richard G, Portmann, Andrea C, Ulrich, Bridget A, Wolfand, Jordyn M
Format: Article
Language:English
Subjects:
Biofilters
Charcoal
Composting
Composts
Contaminants
Flooding
High temperature
Installation
Mesocosms
Microorganisms
Organic carbon
Organic contaminants
Pollutant removal
Pollutants
Pollution load
Receiving waters
Removal
Runoff
Sand
Sandy soils
Soil
Soil contamination
Soils
Solid suspensions
Stormwater
Stormwater quality
Suspended particulate matter
Total organic carbon
Total suspended solids
Urban environments
Water pollution
Water quality
Water treatment
Watersheds
Work capacity
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Summary: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. log 10 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. log 10 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. Stormwater biofilters are being implemented widely in urban environments to provide green space, alleviate flooding, and improve stormwater quality.
ISSN:2053-1400
2053-1419
DOI:10.1039/d0ew00027b