Latest product launches


Posted: Friday 4th December 2009

AN innovative new SUDS-compliant bioretention and bio filtration system from Hydro International could change UK urban street scenes and achieve greatly improved stormwater runoff quality and control in city environments.

As the Government consults on proposals to enforce widespread application of sustainable drainage systems (SUDS) across England, and Wales through the introduction of new national standards, the Hydro Filterra® system could revolutionise the management of stormwater runoff by bringing lessons learned from the USA where it is already extensively installed.

Says Hydro Stormwater division Director Alex Stephenson,. “Hydro Filterra® combines the ‘green’ sustainability of urban planting and landscaping whilst at the same time meeting the key principal of SUDS to control surface water runoff as close as possible to the point of falling.

“Filterra® demonstrates perfectly how a mix of ‘soft’ and ‘hard’ SUDS elements can improve upon traditional design practices to offer a more suitable solution for space-limited urban environments. It puts powerful, natural stormwater management control back into the city planners’ and architects’ hands as part of SUDS schemes, and could be used to offset issues such as extensively paved-over front gardens.”

From the surface, the Hydro Filterra® system looks like a normal tree box, with suitable plants, shrubs or a tree protruding through a decorative grating in a typical concrete slab at pavement level. Underneath, it comprises a concrete container with a 75 mm mulch layer, 500 mm to 1000 mm of a unique soil filter medium, an observation/cleanout pipe and an under drain system which is connected to a surface water drain, infiltration or soakaway system or other outfall.

Stormwater runoff from impervious surfaces is channelled into the inlet of the Hydro Filterra® box, and through the mulch, plant and soil-filter medium. Treated water either drains away or can be diverted into an additional storage volume adjacent to the box, as part of a stormwater attenuation or infiltration system. Modular storage or attenuation blocks such as Hydro’s Stormcell® or the Stormbloc® infiltration block are ideal. An emergency overflow bypass facility is used for extreme events.

Hydro Filterra significantly improves upon traditional bioretention and biofilter design, combining specialist engineered media with indigenous shrubs or trees to provide enhanced bioretention and biofiltration in a kerbside device. The advanced design requires 90-95% less land-take than traditional bioretention and provides higher levels of treatment for Phosphorus and Nitrogen, two of the most environmentally damaging causes of nutrient pollution.

Additionally, the Hydro Filterra can be used as either a conveyance system or a source-point infiltration system for surface water runoff control. Hydro Filterra® is very adaptable, and its small footprint makes it more suitable than traditional bioretention cells for hard landscaped inner city streets, car parks, green spaces, piazzas and pedestrian access, residential and suburban localities.

Filterra® is accepted in the USA as a stormwater management device for hard surface developments where planning permission requires the provision of surface water pollution control. For UK planners, landscape designers and developers, Hydro Filterra® offers a SUDS-friendly opportunity to improve runoff control and quality and comply with ever stricter environmental legislation.

For more information about the new Hydro Filterra® Bioretention System, or any of Hydro’s other storm and wastewater management systems, please call 0800 269371, or visit

Read the magazine online

August 2021

About the magazine »
Magazine archive »


Information for advertisers »

Pulsar New Banner
Cranfield University Pulsar Button June 13 buttonwood marketing British Water Water Aid Harvey Communications Huber wateractive