Greening Biofiltration using Nature Based Solutions

Lead Organisation

City of Newcastle

Case Study Background

Working alongside scientists from the University of Newcastle, the Centre for Organic Research (CORE) has designed a new technology that uses household waste to produce a stormwater filter soil. This is a world first and provides a nature-based replacement to the dwindling excavated sand desposits that are currently used in stormwater sand filters. This technology supports the transition to a circular economy model.

Raingardens are small garden beds located along the street featuring soil and plants that slow down and filter pollution in stormwater, so it doesn’t harm waterways and beaches. The raingardens are usually found on street corners where cars can’t park and have more grass-like shrubbery than usual roadside plantings and are set in lowered beds over drains.

The Vision

Rain gardens are used to protect waterways from pollution in storm water runoff. The City of Newcastle was the first council to trial the use of biofilters for their rain gardens, which use 100% recycled materials including recycled glass instead of virgin glass and household compost instead of artificial fertiliser and clay.

The unique material can remove pollutants such as sediment and heavy metals that come from our tyres and brake pads as they wear down; grease, oil, petrol and air conditioner coolant that drips from motor vehicles; and excess nutrients from parks and gardens that can cause algal blooms.

The water is carried away through drains, pipes and channels to local creeks, wetlands, estuaries and finally to the ocean, which is a great outcome for the environment. Biofilter raingardens have now been installed at sites in Cooks Hill, Merewether, Mayfield West, Stockton, The Junction and Wallsend. Existing systems in Beresfield and Fletcher will soon be renewed with biofilter material.

Benefits and Results

The biofilter alternative has a faster flow rate than traditional methods and is therefore a more efficient material to use. It requires less virgin resources, no fertiliser and have a higher resilience to weather conditions. The biofilter material also supports increased plant species and wildlife biodiversity compared to conventional rain gardens.

Biofilters absorb more heat than conventional rain gardens, resulting in the cooling of streets in hot conditions. It has a higher cost-beneft than conventional sand filters and lower construction and maintenance costs. It can also be reprocessed or composted at the end of its life.