Alpheus Environmental Ltd was employed by motorway services provider MOTO Hospitality Ltd as principal contractor to design and build a replacement effluent treatment plant for the busy motorway services at Winchester. WPL Ltd, Alpheus’ partner for this project, provided the process design, manufacturing, mechanical and electrical installation, supply and commissioning of all the treatment equipment.
When the Motorway Service Area (MSA) at Winchester, then operated by Roadchef, opened in 2000, WPL Ltd designed and installed a sewage treatment plant which managed the wastewater from the site. In recent times this had been identified as undersized for the increasing visitor numbers prior to and after the site was acquired by MOTO in 2008. The site, situated on the M3 between junctions 8 and 9, serves both sides of the M3 with two filling stations and amenity buildings with restaurants, cafes, toilets and shops plus a 40 bedroom lodge.
To deal with increased flow levels and a more stringent discharge consent imposed by the Environment Agency, MOTO awarded a contract to Alpheus Environmental to install a replacement sewage treatment plant. WPL Ltd designed and supplied the SAF-based plant to meet the consent limits of BOD 20mg/l; TSS 30mg/l; NH4-N 10mg/l.
It was imperative that the MSAs remained open throughout the transition and that construction work caused minimal disruption to the operation of the MSAs and its visitors. Due to limited land availability and the presence of existing drains and other services, the part new treatment plant had to be sited at the same location as the original plant. These two issues presented a number of technical challenges during the planning phase, and generated a range of health and safety considerations since construction was undertaken on an existing operational site.
In order to allow the MSAs to remain open throughout the installation, Alpheus Environmental and WPL Ltd installed a temporary treatment plant comprising two small Submerged Aerated Filter (SAF) units, a lamella plate separator and a micro-screen. After an initial seeding process, effluent from the temporary plant was monitored on a weekly basis. Once the effluent reached the consent standards, it was possible to rely solely on the temporary plant for treatment. Removal of the old plant then commenced, followed by the installation of the part new plant.
During peak construction periods, the existing, temporary and some of the new process units were required to operate at the same time, while construction activities continued around them. To a less-experienced team, managing all of this on such a small site could have proved a logistical nightmare. However, with project management and planning expertise from Alpheus Environmental and WPL’s specialist plant design expertise gained from similar size projects, the task was completed smoothly and efficiently.
The team also identified that throughout these works it was not necessary to tanker excessive amounts of sludge or sewage off site as this could interfere with the replacement work and would prove extremely costly to the Client. The existing process tanks on site were used to store and dewater sludge, which minimised off-site sludge disposal.
Up and Running
The new system became fully operational, meeting all consent limits from 19th November 2010. The new sewage treatment system comprises a balance tank, screen chamber, 6m diameter conical primary settlement tank, flow splitter, four SAF units, kiosk with four blowers and control panel, lamella plate separator, V-notch flow chamber and final effluent pump chamber. The balance tank, kiosk, V-notch flow chamber and final effluent pump chamber formed part of the old plant and were re-used with the new equipment to minimise capital costs.
Despite a complex project, Alpheus Environmental and WPL Ltd were able to decommission and remove the redundant sewage treatment plant and install the new SAF plant whilst maintaining effluent discharge standards – without disrupting the MSA.
MOTO Hospitality Project Manager Terry Luckett commented: “Alpheus Environmental and its partners focus on health & safety to ensure successful and safe delivery of the project. The project was completed on time and to budget with the new plant performance meeting expectations. It has allowed us to focus on delivery of our service to our customers.”