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Setting the Standard for Wetland Treatment

Post on: Feb. 19, 2015

Small sewage discharges (SSDs) are a big deal for water quality.  There are estimated to be hundreds of thousands of isolated properties in the UK that are not connected to mains sewerage, and there is no central record of where these are or how effectively the wastewater is treated.  Poor quality SSDs are thought to be a significant contributor to diffuse pollution in many rural river catchments.

When owners of SSDs look to improve the quality of treatment, a wetland treatment system can often be the best choice, as they achieve a high standard of treatment, have very few moving parts, are relatively maintenance free, and need little energy to operate.  Such work is the bread and butter of many members of the Constructed Wetland Association (CWA).

In 2013, DEFRA launched an initiative to reform the legislation surrounding SSDs to try to simplify their regulation. Part of their approach to this has been to offer householders exemption from an environmental permit if their discharge complies with particular “standard binding rules” relating to the location and size of the discharge and the type of treatment system.

The original rules were drafted such that only “package treatment systems” qualify for the exemption.  Package treatment systems are miniaturised mechanical wastewater treatment works that are bought ‘off the shelf’.  The reason they qualify for the exemption is that the Environment Agency consider them to be “Low Risk” as long as they meet the British Standard EN 12566 and are installed and maintained correctly.   In many cases however, a passive approach such as a wetland treatment system may be a better engineering solution than a package treatment system.   Wetland treatment systems tend to be more robust to effluent variations, require less maintenance and low power, yet they do not qualify for the exemptions under the original rules because there hasn’t been a ‘1 size fits all’ industry standard design that can be pre-approved by the Environment Agency.

The CWA has been working closely with the Environment Agency to resolve this issue, and has convened a workshop of some of the leading designers within its membership to develop a standard for vertical flow wetlands to treat small sewage discharges to a high and consistent quality.

CWA members from Eco-tech Systems, WWT Consulting, Wildfowl & Wetlands Trust (WWT), ARM Group Ltd, Cress Water Solutions, Moir Environmental Limited, and Watercourse Systems took part in the Design Workshop

We are optimistic that once the new standard has been agreed and published by the CWA, the Agency will be able to change its rules to allow householders to choose a low maintenance, low energy treatment systems without the need to apply for an environmental permit.