Hydraulic properties of stormwater biofilters during dry phase

ABSTRACT

Stormwater biofilters operate in alternating wet-dry cycles and subjects processes to distinct environmental conditions, particularly, moisture content. Pollutants in residual water may undergo chemical or biological transformation during the dry phase and affect pollutant removal. The study aims to analyse filter water content during dry-cycle. Ten Perspex bioretention columns (94 mm internal diameter) were fed with tapwater at 100 mL/min for three hours and the filters were left to dry for 40 days. Filter material samples were obtained at different depths after different number of dry days (0–40 days) and were tested for moisture content. Top 5 cm had moisture content decreased to wilting point (6% degree of saturation) while deeper layers stabilised at higher degrees (40%). A mathematical model developed indicates significant amounts of moisture being held in the filter during the dry-phase, indicating potential impact on pollutant removal performance of the filter.

KEYWORDS:

• Stormwater biofilters
• antecedent dry days
• depth in filter
• moisture content

Acknowledgements

The authors would like to thank River Sands Pty Ltd, Australia for supplying the stormwater biofilter packing material for my experiments. The authors also would like to thank Queensland University of Technology and University of Jaffna for providing funds for the study.

Disclosure statement

No potential conflict of interest was reported by the author(s).