Waste, sediment and pollutant traps
Traps installed in stormwater drains and other waterways can screen, slow down and remove waste, sediment and pollutants from water. They reduce waste entering waterways and wetland systems, and improve water quality in catchments.
Pollutants, such as litter, sediment, nutrients, pesticides and heavy metals, are generated from a variety of land uses. They can degrade the condition and function of wetlands, groundwater and coastal and marine ecosystems.
Used in conjunction with best practice land management, traps can improve water quality on a catchment-wide scale.
Treatment wetlands are a type of pollution trap that help prevent waste reaching waterways, such as rivers and streams. They capture waste in the environment, allowing manual waste removal or waste breakdown processes. However, allowing waste to enter a natural wetland may have negative effects on the ecosystem and is not considered best practice. Any consideration of the use of a natural wetland should be based on sound research and assessment of impacts.
Constructed treatment systems
Constructed treatment systems can be used to remove pollutants and improve the quality of runoff water in urban areas. Oil, toxic chemicals and other pollutants washed from roads and roofs all impact water quality in our urban landscapes.
Use of sediment traps is one of many techniques for reducing runoff pollutants from many areas, for example earthworks and construction sites.
Vegetated buffers and swales
Buffers are strips of vegetation, such as trees, bushes and grass that can be used to effectively separate wastewater from a waterway or wetland. Swales are sunken hollows or channels that can capture and divert runoff and other wastewater. Buffers and swales can be useful in reducing and trapping waste in runoff water. This can include sediment and nutrients from paddocks, chemical waste from industrial sites and rubber from roads. Riparian buffer strips can also help reduce stream bank erosion, provide wildlife habitats and connect landscapes.
Litter booms are traps that float on the water surface of freshwater, intertidal and marine areas to collect litter. Floating booms may also be extended across creeks, weirs or dams to capture floating waste and prevent it from travelling further downstream. Installed across waterways or in oceans, these systems also act as a final barrier to collect or deflect debris and oil. Booms can be combined with litter collecting wheels and conveyors to collect and remove waste.
While litter booms can be effective, they are usually made from lightweight PVC and could potentially increase microplastics in the water.
High flow bio-filtration technology
These technologies are optimised for high volume/high flow treatment and high pollutant removal. They filter, retain and use pollutants on-site, in highly developed situations, such as landscaped areas, parking lots and streets. Stormwater runoff enters the system through an inlet and flows through a filter before discharging to waterways. The filter captures and immobilises pollutants, which are then decomposed and used to fertilise on-site vegetation, such as garden beds.
Gross Pollutant Traps
Gross pollutant traps placed in stormwater drains can collect large waste items as they enter the system. They can include:
Gravity filtration technology
This technology uses gravity and unique filter cartridges to remove high levels of waste in high flow situations. Each filter cartridge has a number of ‘tentacles’ that catch and remove floating waste, oil, debris, suspended solids and tiny particles (as small as 2 microns). The system catches a high percentage of pollutants, including phosphorus, nitrogen, metals and hydrocarbons.
High efficiency coalescing separator
These devices separate out and collect wastes, such as oil, hydrocarbons and grease, to ensure they do not enter waterways.
Stormwater filter systems
Filtration devices are fitted to stormwater drains to capture pollutants such as heavy metals, suspended solids, hydrocarbons and nutrients. Several filtration systems of varying size can be used together, stopping a range of different items entering the stormwater system. Other features of filter systems include:
Full capture storm drain netting systems
These netting systems are engineered to capture gross pollutants and handle high-volume stormwater runoff in waste pollution hotspots. Commercial grade and reusable, they capture gross pollutants as small as 5mm, including organic materials (such as leaves) that alter the levels of phosphorous and nitrogen in our water.
Litter-collecting wheels and conveyors
Semi-autonomous litter collectors can be placed at the end of a river, stream or other outfall. These static floating devices use water wheels or conveyors to collect litter as it passes the device. Most are powered by solar or another renewable energy and built to withstand storms. Litter collectors like these can combine with boom trap systems to gather waste and direct it to an appropriate collection point.
In-water oil and litter removal systems
This technology skims the surface of estuarine surface waters, e.g. marinas and ports, to remove oil and floating waste. These systems can be effective, but they need regular servicing, similar to bins on land.
Microplastic laundry filters
Microfibres, including microplastics, are released into wastewater systems with each load of laundry. The technology exists to capture and prevent these materials entering wastewater systems, including filters attached to commercial and residential washing machines.
These filters clean marine waste from the water surface and water column to a depth of about 3 metres. They may be solar or wind powered and can clean a wide range of waste types, up to a metre in size.
Litter fences are designed to go around the perimeter of locations such as waste facilities, to reduce the risk of waste escaping the site. Litter fences are designed to force waste toward the bottom of the barrier under high wind conditions. Outriggers insure that waste will not go over top of fence. Netting is completely removable from the cable system and poles can be installed for relocation.
Last updated: 10 May 2021
This page should be cited as:
Department of Environment and Science, Queensland (2021) Waste, sediment and pollutant traps, WetlandInfo website, accessed 13 May 2021. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/management/pressures/litter-illegal-dumping/management-interventions/treatment.html