Zero additional maintenance stormwater biofilters: from laboratory testing to field implementation

Stormwater biofilters are one of the most widely used nature-based solutions for urban water management. In the last 20 years, biofilters have been extensively studied for their pollutant removal performance; however, their application in the field is limited by high maintenance requirements. In this work, we propose the concept of zero additional maintenance (ZAM) biofilters as a solution to this challenge. To understand the design and operation of ZAM biofilters, a three-stage research programme was conducted to (i) examine filter media configurations that could protect against surface clogging, (ii) test the pollutant removal performance of a variety of lawn grasses, and (iii) validate the laboratory findings through field monitoring. The results showed that a protective filter media layer delayed the onset of clogging. Five lawn grasses - Kenda Kikuyu, Empire Zoysia, Santa Ana Couch, Village Green Kikuyu and Palmetto Soft Leaf Buffalo - were found to effectively reduce nitro-gen concentrations and meet other local pollution reduction requirements. Monitoring of three field-scale ZAM biofilters confirmed their high nutrient and heavy metal removal performance. Overall, the findings of these three studies confirm the potential for well-designed ZAM biofilters to achieve stormwater management requirements with no additional maintenance compared with standard street landscaping.