Bioretention channel systems for surface water pollution control
With increasingly intense, frequent, and extreme weather events, there is a need to mitigate the flooding and pollution risks caused by uncontrolled surface water run-off. D-Rainclean is a robust, 300mm polypropylene channel drainage system with a unique bio-retention medium. The system deals with surface water run-off and treats the flow at source, making it an ideal treatment component in a Sustainable Drainage (SuDs) solution.

Flooding and pollution

Pluvial flooding has become a regular occurrence as our drainage networks become incapable of coping with increased urbanisation combined with climate change. Since the turn of the millennium, the construction industry has sought to tackle the problems associated with more intensive rainfall, and in particular the volumes of water generated. This culminated in the Flood and Water Management Act 2010, which sets out the responsibilities for the design, construction, and maintenance of sustainable drainage systems. What is perhaps less well known is that, enshrined in this legislation, is the requirement to address surface water quality leaving development sites in order to comply with the Water Framework Directive. Much of the onus to comply with the FWM Act falls on Local Authorities whose role it is to mitigate and minimise both flood and pollution risk by ensuring that hard-lansdcaping design and installation ‘design-out’ and build-out’ both flood risk and pollution risk, usually by employing SuDs techniques.



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The solution

WRS-USA offer the highly innovative and proven D-Rainclean porous channel and bio-retention filter media system that treats the priority pollutants identified by the regulatory authorities (Environment Agency and Highways Authority), principally total suspended solids (TSS) and dissolved heavy metals such as copper and zinc – meeting both these key requirements within a single solution.


D-Rainclean comprises a 300mm polypropylene channel system filled with a unique engineered bio-retention filter media that treats run-off from any impermeable surface. Using the processes of separation, adsorbtion, absorption, and bioremediation D-Rainclean allows contaminated run-off to be treated to a sufficient quality to allow infiltration back into the ground at the closest point to its generation, meeting one of the key requirements in drainage hierarchy – ‘source control’. D-Rainclean uses a unique engineered bio-retention filter media containing selected natural minerals with a high cation exchange and filtration capacity. These media clean surface water as it passes through the filter layers, degrading and diffusing hydrocarbons, and dissolved heavy metal like copper and zinc. A properly installed D-Rainclean system can drain areas of up to one hectare and the system has been proven to meet the stringent requirements set down by the DIBt.

Filter media

D-Rainclean Filter Media is a unique series of media that perform different functions in order to clean surface water runoff using the processes of filtration, adsorption, ion exchange, phosphate and retention.

Filtration Many contaminants attach themselves to sediment particles. The smaller the particle, the higher its concentration. The filter-media in D-Rainclean retains these sediments by depth filtration, ensuring they are retained in the upper 5-10cm of the filter media. This significantly reduces the risk of surface clogging (colmatage) and ponding, particularly in extreme events, something which some surface filtration systems, such as permeable paving are prone to.

Water retention

Soil microbiology performs a valuable degradation role, particularly during periods of warmer weather. As such the D-Rainclean filter media retains moisture to allow this degradation process to occur. Large pore spaces within strata of the media combined with organic substances and the design of the D-Rainclean channel allow 3.0 litres per linear metre to be stored to ensure that this optimised process can occur. Soil Testing Values* Arsenic (As) 10 μg/l Lead (Pb) 25 μg/l Cadmium (Cd) 5 μg/l Chromium (Cr) 50 μg/l Copper (Cu) 50 μg/l Nickel (Ni) 50 μg/l Mercury (Hg) 1 μg/l Zinc (Zn) 500 μg/l

Hydraulic capacity

The D-Rainclean filter media has a water permeability coefficient of 9 x 10-4 m/s, the secret to this high permeability rate is due to the graduated grain sizing within the media that produces a widely spaced distribution curve. The coefficient has been derived by testing which allows sufficient detention time for adsorption to occur. The water reservoir built into the channel design also ensures that soil microbiology continues to occur and does not dry out during extreme dry spells

Harmful organic materials

D-Rainclean uses an organic matrix and a specific activated carbon that supports bonding and degradation of organic pollutants, as such D-Rainclean degrades mineral oils from impermeable trafficked areas such as car parks.

De-icing salts

The use of de-icing salts can block adsorption and reverse the adsorption of already captured hazardous material. The performance of the filter-media is not adversely affected by sodium chloride even in shock loads. However frequency and concentration of de-icing will have an effect on overall service life.

For more information on Stormwater Treatment Solutions offered by WRS-USA please contact the sales office on(859)307-5512 or email us Info@wrs-usa.com