Seedy Mill is South Staffs Water’s second largest water treatment works. It takes water from Blithfield Reservoir, treats it and sends it to customers from Burton to Walsall and throughout the area between.
However it was first built in the 1950’s and, notwithstanding numerous modifications and extensions since, it was still using the same processes it used when first built. Water quality requirements have changed dramatically and the works no longer met current standards.
To address this new ultraviolet light treatment process was superimposed into the treatment stream.
This process uses ultraviolet light to disinfect the water as it passes through and ensures any bacteria or viruses are destroyed. This has the advantage of ensuring that less potentially harmful chlorine is needed to kill the bugs and reduces the chance of taste problems with the final water.
The project was initiated in July 2015 with a brief of treating all water into supply before the end of May 2016.
The main aim of the project was to improve the disinfection process at the works whilst keeping it operational at all times and providing sufficient water for customers.
This was complicated as there was very little available space at the works and very limited hydraulic headroom.
The decision was taken to install the new UV system inside the existing two halves of the contact tanks which would be converted into dry chambers to house the new equipment.
This involved decommissioning the 50 year old contact tanks, removing the roof and making major structural alterations. The new UV plant was then installed with the necessary pipework, instrumentation and control measures.
The North and South halves of the contact tank were converted separately in order to maintain works output.
The challenges which had to be overcome to deliver the project included major modifications to old concrete structures, and ensuring that water would still flow through the existing pipelines without restriction when the new process was introduced.
In addition, water quality parameters which the works has never measured before are now being used to successfully control the new process.
The client’s approach to project delivery was complete openness and flexibility. The selection of a IWS was done within three weeks of the project initiation and was done by evaluation of the attitude and skills that IWS would bring to the process.
This meant a completely collaborative approach from the start as both IWS and the main supplier were selected before there was even an outline design to price against. This had the benefit for South Staffs Water that the project team could hit the ground running and start construction work before the designs were even vaguely complete.
The contract price was established by open book principles whilst the design was ongoing. Similarly the main UV supplier had a large input into the design process and the final design is both innovative and effective using a syphon downstream of the UV system to instantaneously prevent forward flow of water in the event of a problem with the UV reactors.
South Staffs Water has several other UV projects to complete in AMP6 and the lessons learned have been invaluable. Whilst the other projects may not have the same time constraints they have benefitted from both the technical lessons regarding the UV systems and the design parameters which are critical.