Upgrading a 1950s Water Treatment Works

South Staffs Water supplies approximately 1.3 million people and 35,000 commercial customers with clean water over 1,500 square km in the West Midlands, South Staffordshire, South Derbyshire, North Warwickshire and North Worcestershire. Seedy Mill WTWs near Lichfield, is the company’s second largest surface water treatment works, serving a population of 200,000, and is critical to the region’s water supply. Constructed in the 1950s, until recently it was still basically using the same process as when it was first built. Water from the Blithfield Reservoir was treated by coagulation, flocculation, sedimentation and filtration then disinfected using chlorine.

In July 2015 South Staffs Water began a project to improve the disinfection process at Seedy Mill. The decision was made to install an ultraviolet system for primary disinfection. In order to comply with South Staffs Water regulatory requirements, the project had to be completed by the end of May 2016: a tight deadline to identify, design and install a state-of-the-art technical solution. And, of course, the works had to remain operational throughout the project to guarantee the water supply to South Staffs Water’s customers in the area.

Early in the project, South Staffs Water selected Evoqua, whose equipment is third party validated in accordance with the US EPA protocol, and paired them with M&E installation contractor Integrated Water Services. Owing to time constraints, construction work started while the design was still being developed, which meant that the two companies were able to contribute to all aspects of the project development, reducing some costs and producing a final design that was both innovative and effective.

Three leaders (one from each organisation) were selected to work together to drive the project, and all signed up to a fast-track decision making process to meet the required deadline. This meant that efficiency was enhanced at every stage of the construction process. Trust in the relationship, teamwork and strong leadership replaced many of the normal contract formalities. It was agreed that the project would be a totally collaborative success or failure with a ‘no-blame’ culture. This completely transparent approach and lack of hierarchy in the project gave the team a culture of mutual support that it is now taking forward on future projects.

The ATG™ UV system to meet the required 120Ml/d flow rate consisted of four UVLW-30800-30 reactors each fitted with thirty of Evoqua’s innovative high efficiency 800W UVLX Amalgam low pressure UV lamps. These offer a range of benefits including guaranteed lamp life of 16,000 hours, optimized UV reactor design for reduced low headloss and a compact installation footprint. The ultra-high output of the 800 Watt Amalgam UV lamps reduces the number of lamps, quartz tubes and seals by over 50% by comparison to traditional 330 watt systems, giving significant capital and operating cost savings.

Technical challenges included major modifications to the two halves of the old underground concrete contact tank to provide a space for the UV reactors, and ensuring that there was enough hydraulic head to drive the water through the existing pipelines and the new process plant. The two halves were converted in separate phases to keep the plant operational. Seedy Mill is a gravity flow works and a specialised syphon system (one of the largest of its kind) had to be designed and installed downstream of the UV system to allow instantaneous shutdown if required. The design changed throughout the project to meet technical challenges but, due to the partners’ support and flexibility, Seedy Mill remained operational with no interruptions to supply and no lost time injuries. Despite being one of the largest UV plants in the UK, Seedy Mill has a lower power consumption as it uses a low-pressure lamp system with low headloss reactors.

So successful was the collaboration between South Staffs Water, Integrated Water Services and Evoqua that the team was a finalist for Partnership of the Year for collaborative work at this year’s Water Industry Achievement Awards.