The influence of vegetation in stormwater biofilters on infiltration and nitrogen removal: Preliminary findings

Abstract

<p>This study provides new information on the influence of vegetation type on the infiltration rate and removal of nutrients in biofilters. Compared to previous studies, a wider range of plant species (11 species native to Western Australia, and 11 native to Victoria) and plant types (lawn grasses, grasses, sedges, rushes and shrubs) were examined in a laboratory-column study. The preliminary results indicate that the presence and type of vegetation influence infiltration rate and nitrogen removal in biofilters. In the early stages of the experiment, vegetation reduced the infiltration rate of columns as compared to soil-only controls, but over time this trend began to change, with. Importantly, whilst all plant species were able to reduce effluent concentrations for Total Nitrogen (TN) and nitrogen oxides (NO <sub>x</sub>), soil-only control columns leached NO <sub>x</sub>. Columns with submerged zones universally resulted in greater reductions in concentration for TN and NO <sub>x</sub> than traditional non-submerged columns (although the differences were often minor). Whilst there were some differences in removal performance between plant species, these differences were also relatively small, with TN outflow concentration averaging 0.44 mg/L and 0.26 mg/L for non-submerged and submerged columns respectively, an 80% and 88% reduction from the inflow concentration of 2.27mg/L. These preliminary results demonstrate that as long as the media is carefully selected, designers can choose from a relatively wide range of plant species and still achieve effective nutrient removal.</p>