title: Biofilter design for effective nitrogen removal from stormwater - influence of plant species, inflow hydrology and use of a saturated zone.
abstract: The use of biofilters to remove nitrogen and other pollutants from urban stormwater runoff has demonstrated varied success across laboratory and field studies. Design variables including plant species and use of a saturated zone have large impacts upon performance. A laboratory column study of 22 plant species and designs with varied outlet configuration was conducted across a 1.5-year period to further investigate the mechanisms and influences driving biofilter nitrogen processing. This paper presents outflow concentrations of total nitrogen from two sampling events across both 'wet' and 'dry' frequency dosing, and from sampling across two points in the outflow hydrograph. All plant species were effective under conditions of frequent dosing, but extended drying increased variation between species and highlighted the importance of a saturated zone in maintaining biofilter function. The saturated zone also effectively treated the volume of stormwater stored between inflow events, but this extended detention provided no additional benefit alongside the rapid processing of the highest performing species. Hence, the saturated zone reduced performance differences between plant species, and potentially acts as an 'insurance policy' against poor sub-optimal plant selection. The study shows the importance of biodiversity and inclusion of a saturated zone in protecting against climate variability.
authors.affiliation: Department of Civil Engineering, CRC for Water Sensitive Cities, Water for Liveability Centre, Monash University, VIC 3800, Australia E-mail: emily.payne@monash.edu.
authors.forename: Emily G I
authors.initials: EG
authors.lastname: Payne
authors.affiliation: Department of Civil Engineering, CRC for Water Sensitive Cities, Water for Liveability Centre, Monash University, VIC 3800, Australia E-mail: emily.payne@monash.edu.
authors.forename: Tracey
authors.initials: T
authors.lastname: Pham
authors.affiliation: School of Chemistry, CRC for Water Sensitive Cities, Water Studies Centre, Monash University, VIC 3800, Australia.
authors.forename: Perran L M
authors.initials: PL
authors.lastname: Cook
authors.affiliation: Department of Resource Management and Geography, Melbourne School of Land and Environment, The University of Melbourne, VIC 3212, Australia.
authors.forename: Tim D
authors.initials: TD
authors.lastname: Fletcher
authors.affiliation: Department of Civil Engineering, CRC for Water Sensitive Cities, Water for Liveability Centre, Monash University, VIC 3800, Australia E-mail: emily.payne@monash.edu.
authors.forename: Belinda E
authors.initials: BE
authors.lastname: Hatt
authors.affiliation: Department of Civil Engineering, CRC for Water Sensitive Cities, Water for Liveability Centre, Monash University, VIC 3800, Australia E-mail: emily.payne@monash.edu.
authors.forename: Ana
authors.initials: A
authors.lastname: Deletic
mesh_terms: D062070:Hydrology; D009584:Nitrogen / Q000302:isolation & purification*; D010944:Plants; D014739:Victoria; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification; D014904:Western Australia; D053833:Wetlands
chemical_list: D014874:Water Pollutants, Chemical; D009584:Nitrogen