The arrival of WPL’s TWTM (Transportable Wastewater Treatment Module) at Southern Water’s Dunbridge site, near Romsey, gets the £1m refurbishment project well underway.

The Dunbridge wastewater treatment works serves around 190 people and is set in local woodland. Southern Water’s contractor, 4Delivery, has prepared the site with guidance from the Forestry Commission ready for the refurbishment work to begin.

The new works will be inside the existing footprint and provide even better biological wastewater treatment, which is then recycled back into the local environment.

The WPL TWTM is part of a complete temporary wastewater treatment works installed above ground adjacent to the exiting works. This allows the existing works to be completely removed and replaced with the new, permanent below ground plant (also by WPL) with no interruption of service to local residents. It will provide temporary, biological wastewater treatment for the duration of the upgrade.

The Dunbridge site has a narrow entrance and is also on an incline. The WPL TWTM supplied (a T300) has a small footprint and it’s compact design aids delivery to sites with restricted access.

The TWTM range of treatment solutions can provide temporary or permanent above ground treatment for population equivalents from 50-5000, depending on the individual site requirements. All mechanical and electrical components are housed in a separate weatherproof kiosk for easy maintenance. WPL also has a Service Team offering mechanical and electrical installation of their plants.

WPL TWTM units use WPL SAF (Submerged Aerated Filter) technology and offer consistent process reliability sub 2mg/L ammonia and 10mg/L BOD, and are suitable for variable flows and loads.

The new permanent plant for Dunbridge wastewater treatment works will be the WPL HiPAF below-ground solution, to be delivered in September 2012. The HiPAF also uses SAF technology and consists of primary, biological and final humus sections. HiPAF’s can achieve discharge standards of BOD 10mg/L, SS 10mg/L and Ammonia 2mg/L (with tertiary treatment), meeting demanding Environment Agency discharge consents.

As the Dunbridge site is restricted due to the incline and its existing boundaries, the WPL HiPAF solution will be configured into a modular system, consisting of separate primary tank, a SAF (biological treatment) tank and a combined SAF/humus tank. A separate kiosk will also house the form 2 control panel plus the duty and standby air blowers that provide aeration to the SAF units. The consent standard for this site is BOD 40mg/L, SS 60mg/L and Ammonia 5mg/L.

The Dunbridge scheme completed in March 2013.