Increasing raw water color from the reservoir catchments, associated with higher intensity rainfall events (believed to be linked with global warming), have put the existing clarification processes under increasing challenge. In order to future proof the works against this, a substantial enhancement project has been undertaken over the past three years (2009 to 2012). A joint venture between Vinci Construction and MWH has been established to design and construct this £34M scheme in three work packages. Briefly, these are:
A new disinfection stage contact tank with associated hypochlorite and bisulphite dosing equipment.
A new lime plant (to control pH throughout the treatment processes) and upgrade of the existing orthophosphoric acid dosing plant.
A new Dissolved Air Flotation (DAF) clarification plant and sludge thickeners along with refurbishment/replacement of the associated chemical dosing equipment.
New RC contact tank 75m x 20m x 6m giving a 30 minute contact time
Built within the footprint of a redundant clear water reservoir.
Complete with integral valve chamber which, in an emergency, is able to draw down into supply in a bottom operated penstocks; these can be opened to bypass an existing Balance Tank which acts as a header tank on the DVA.
Contains two compartments to facilitate cleaning and maintenance.
Internal walls are full height RC.
High level outlet weir with associated overflows and under-drainage systems.
All interconnecting pipework up to 1800mm dia. to valve chamber and Derwent Valley Aqueduct.
Dosing equipment to ensure compliance with disinfection standards.
Water quality monitoring, SCADA and MCC controls.
Construction of a Lime Plant to control the pH profile throughout the whole treatment process; this replaces the existing Lime and Kalic dosing plants.
Provision of storage silos and mixing tanks giving 28 days storage and providing 27.5 m3 working capacity.
Provision of new duty / standby dosing pumps to dose lime slurry at four different stages.
New process water and carrier water systems.
Construction of a new Orthophosphoric Acid dosing rig and associated dosing lines.
Drainage systems to ‘Chem e Safe’ requirements.
Systems integration and SCADA.
MCC and electrical installation.
Replacement of clarification stage on North and South Plants with a single DAF Plant, built within old slow sand filters 4 and 5.
Installation of two raw water inlet mains with chemical mixing, from the existing South Plant Inlet Works to the new DAF Plant.
Provision of three routes from the DAF Building outlet mixing chamber to convey clarified water to the following locations: the North Plant Filters 1-6, South Plant Filters 1-16 and 17-22.
Construction of two sludge thickening plants and polymer dosing facilities to thicken DAF and Lamella sludge local to the new DAF plant.
Ferric Sulphate dosing facilities for coagulation of raw water.
Disinfection post DAF plant and an emergency dosing system pre Contact Tank.
Complete electrical installation system, energy metering, control gear, switchgear, instrumentation, systems integration, lighting and lightning protection.
The project team looked to add lasting value to the scheme by introducing cost effective innovation wherever possible. Through waste minimization, material selection and design best practice, the carbon savings on the new facilities at Bamford WTW have. Some examples of how this has been achieved include:
The original clear water reservoir concrete walls were crushed and reused for the new road construction; carbon saving 14 tonnes.
Use of permanent formwork for the Contact Tank roof providing health and safety benefits during construction; carbon saving 22 tonnes.
Used site-derived excavated material as backfill to the Contact Tank; carbon saving 33 tonnes.
Pipe bedding material changed from gritstone to limestone reduced transportation from local quarry; carbon saving 59 tonnes.
Changed pipe material from ductile to coated carbon steel; carbon saving 9 tonnes.
Contact Tank under-tank drainage changed to perimeter drainage; carbon saving 59 tonnes.
First use of Weholite pipework on a STW water treatment works – used instead of ductile pipework for DAF inlet / transfer mains; carbon saving 439 tonnes.