Installation of Graf sewage treatment plant as part of Free Septic Tank Upgrade scheme

The owners of ‘Windwhistle’ registered for a free septic tank upgrade in 2023 in response to WCI’s scheme to reduce nutrient pollution across Somerset. The property sits within the River Tone hydrological catchment, a key tributary of the Somerset Levels and Moors Site of Special Scientific Interest.

‘Windwhistle’ was approved onto the scheme in August 2023 and a comprehensive site survey was completed to assess the location of the existing septic tank, confirm the discharge to ground, assess the access considerations and ground conditions.

WCI proposed an upgrade to a GRAF UK one2clean package treatment plant. Market leading for its eco efficiency and ability to reduce phosphate levels, the one2clean would create the necessary phosphate ‘betterment’ in the River Tone catchment.

In May 2024 the property owners entered into an agreement with WCI for the upgrade of the septic tank and a separate planning agreement (S106) with Somerset Council committing to keep and maintain a compliant system. A week later, WCI were installing the new one2clean – just one of hundreds being upgraded through WCI’s free septic tank upgrade scheme.

After seemingly endless days of rain, we were granted some dry weather for the installation – and a welcome flow of teas and coffees! Rubber mats were laid to protect the lawn from heavy machinery and the team started with a partial excavation of the new treatment plant site to test ground conditions. Excavation was completed by day two of the project and the GRAF one2clean was installed in accordance with the manufacturer’s installation guide and surrounded in concrete. The existing septic tank was emptied and decommissioned.

Electrical connections were made to the new sewage treatment plant with the air blower kiosk discreetly sited behind a bush in the garden.

With the new sewage treatment plant installed, the area was made good with imported topsoil, the area grass seeded, and the daffodil bulbs replanted. The GRAF system was commissioned by a WCI British Water and GRAF Accredited Service Engineer.

The successful upgrade resulted in a phosphate reduction of 1.01 kg of Total Phosphorous (TP) per year. The property owner was extremely satisfied with the outcome and benefits from five years of free WCI servicing to ensure the system’s optimal performance.