Abstract
Bioretention systems are a popular type of Sustainable Drainage System (SuDS). However, their largest single component, the fill media, is often a non-sustainably sourced material. This study evaluates a bioretention fill media comprising 100% recycled waste components. The fill media components come from multiple waste streams, quarry waste from the construction sector, crushed glass and green waste compost from domestic waste, and sugar-beet washings from the food processing sector. The hydraulically important physical characteristics of the recycled fill media were evaluated against reported literature examples of bioretention fill media, alongside UK and international guidance documentation. The particle size distribution of the recycled fill media was found to be unlike that seen in the literature and was also not compliant with the UK’s CIRIA ’The SuDS Manual’ guidance (d≥6 mm = 45% vs. 0% target). However, this did not result in any additional non-compliance, with laboratory-derived saturated hydraulic conductivity (Ks=101 mm/h) and porosity (ϕ=44%) within recommended ranges (100≤Ks≤300 mm/h, ϕ>30%). SWMM was used to predict the performance of a bioretention system installed with the recycled fill media compared to UK guidance configured systems. It was found that the recycled fill media would have similar performance to a UK guidance compliant system, irrespective of its particle size distribution. Further work is required to validate the predicted performance of the recycled media.
Highlights
This study aims to determine the hydrological suitability of a bioretention fill media whose components are all derived from waste products
A bioretention media composed entirely of recycled waste components was evaluated against reported media configurations in the literature, alongside UK and international guidance documentation, to determine its suitability
The particle size distribution was found to be non-compliant with UK guidance due to material greater than 6 mm in diameter as a result of included quarry waste
Summary
Based Solutions umbrella terms—in which vegetation and an engineered soil media are used to filter stormwater contaminants and sediments, and reduce stormwater volumes and flow rates [1]. A generic bioretention system will typically comprise: a vegetation layer set within a ponding zone; a fill media layer for water storage, filtration and plant support; and a drainage layer (Figure 1). Traditional bioretention media is a mixture of 30–60% sand, 20–30% soil and 20–40%. Organic matter by volume [2,3,4]. The media is typically chosen to support plant life, and the texture (particle and pore size distributions) and hydraulic conductivity of the fill media govern its hydrological performance. The drainage layer facilitates the exfiltration of water to underlying soils (where exfiltration is permitted) or to the underdrain (where present)
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