Plants release, pathogens decease: Plants with documented antimicrobial activity are associated with Campylobacter and faecal indicator attenuation in stormwater biofilters

P Galbraith; R Henry; D T McCarthy

doi:10.1016/j.scitotenv.2023.167474

Plants release, pathogens decease: Plants with documented antimicrobial activity are associated with Campylobacter and faecal indicator attenuation in stormwater biofilters

Sci Total Environ. 2024 Jan 1:906:167474. doi: 10.1016/j.scitotenv.2023.167474. Epub 2023 Oct 5.

Authors

P Galbraith¹, R Henry², D T McCarthy³

Affiliations

¹ Department of Civil Engineering, Monash University, Wellington Road, Clayton, Victoria 3800, Australia; CSIRO Agriculture and Food, Building 10, 39 Kessels Rd, Coopers Plains, Queensland 4108, Australia.
² Department of Civil Engineering, Monash University, Wellington Road, Clayton, Victoria 3800, Australia.
³ School of Civil and Environmental Engineering, Queensland University of Technology, 2 George St, Brisbane City, Queensland 4000, Australia. Electronic address: david.mccarthy@qut.edu.au.

PMID: 37804974
DOI: 10.1016/j.scitotenv.2023.167474

Abstract

Stormwater biofilters demonstrate promising treatment of faecal microorganisms, however performance can vary with design and operational conditions. This study investigated whether plants with significant documented antimicrobial activity could improve faecal bacterial treatment within biofilters. Laboratory-scale biofilters (n = 30) were dosed with synthetic stormwater containing faecal bacteria Escherichia coli, Enterococcus faecalis and Campylobacter jejuni under south-eastern Australian climatic conditions. Systems vegetated with Melaleuca species, renowned for their in vitro antimicrobial activity, consistently enhanced removal of all tested culturable bacteria in total outflow and submerged zone water relative to other plant configurations. Within just 1-2 days of stormwater dosing, M. linariifolia submerged zones demonstrated significantly reduced bacterial concentrations compared to C. appressa (p = 0.023 and <0.001 for C. jejuni and E. coli, respectively), removing ∼1.47 log₁₀ MPN/100 mL E. coli, ∼1.14 log₁₀ MPN/100 mL E. faecalis and ∼0.81 log₁₀ MPN/L C. jejuni from inflow. These trends continued even after all but one M. linariifolia replicate perished during an extended drying period (p = 0.002 and 0.003 for C. jejuni and E. coli, respectively). Through a systematic process of elimination, these observations were attributed to enhanced bacterial attenuation with elevated plant inhibitory activity. Cumulative biofilter age reinforced plant-mediated bacterial treatment (p = 0.023 for E. faecalis), ostensibly due to increased plant size/growth and net biological activity. Notably, E. coli and E. faecalis attenuation improved with prolonged antecedent drying length (14 vs. 4 days; p < 0.0001 for both), while the converse was observed for C. jejuni (not significant). This study addresses significant knowledge gaps around plant-mediated faecal microbe treatment within biofilters, providing key direction for real-world system design to optimise stormwater pathogen treatment.

Keywords: Antimicrobial; Biofilter; Campylobacter; Fecal microorganisms; Urban stormwater; Vegetation.

MeSH terms

Australia
Campylobacter*
Escherichia coli
Filtration
Rain
Water Purification*