Denca’s expertise helps United Utilities deliver the highest quality drinking water

United UtilitiesOnly a handful of people driving past United Utilities’ Wybersley Water Treatment Works in High Lane, Cheshire, will even hazard a guess as to the significant role this state-of-the-art process plant plays in producing safe, clean drinking water for the many thousands of homes and businesses across the Stockport area.

One of the most advanced and efficient water treatment works in the North West, and located on a carefully landscaped 4.5-hectare site, Wybersley was built to supply and improve drinking water quality in line with European standards.

Proposed in 1989, the water treatment works entered the supply network in 1996. Before the creation of Wybersley Water Treatment Works, pressure filter plants at the nearby Goyt Valley, Lyme Park and Kinder reservoirs treated the main water supply for the Stockport area.

Today, raw water for the Manchester South area is sourced from a number of local reservoirs, as well as treated water from the Lake District. Since commissioning in 1996, Wybersley Water Treatment Works has provided as much as 70 million litres of drinking water daily for around 350,000 people, as well as that for local industry.

Outstanding technical support

Supporting the highly skilled Wybersley team, taking responsibility for the reliable operation of the complex PLC systems used in the operation of the water treatment works, and providing essential systems upgrades, Widnes-based control technologies specialists, Denca have worked with United Utilities at Wybersley for the last 15 years.

Unrivalled understanding of requirement

“Denca has an unrivalled understanding of our processes and requirements, as well as a thorough appreciation that Wybersley WTW is able to operate 24 hours a day, 365 days a year without failure,” comments United Utilities’ Senior Technical Officer, Kevin Allen.

“Working as an approved United Utilities’ vendor, Denca has provided high quality technical services to the Wybersley plant virtually since it was commissioned. The company’s expertise spans both technical and operational perspectives, includes the importance of precise record-keeping and delivers first-class service and support whatever the time of day.”

State-of-the-art facility

Employing the very latest water filtration systems, Wybersley is supported by one of the country’s most advanced water quality laboratories.  As a truly state-of-the-art facility, during AMP 4 the site benefited from the construction of a £multi-million Lamella water treatment plant.  The Lamella separation technology is used alongside other filtration processes to remove even the slightest risk of any bacterial contamination, such as Cryptosporidium, from Wybersley’s washwater system.

Three-stage water-treatment process

Drinking water treatment at Wybersley WTW involves a three-stage treatment process, Dissolved Air Flotation (DAF) and First and Second-Stage Filtration.

Raw water is blended at point of inlet and quality checked for pH, turbidity, colour, conductivity and temperature. From here it passes into the first stage of clarification where coagulant is added to bond solid particles together.

The coagulated water then passes into flotation tanks where air is injected to make any particles of solid matter float to the surface for scraping off and subsequent recycling into sludge cakes for use in agriculture.

In the second and third filtration stages, the water is directed through a series of sand filters where impurities such as soluble aluminium and manganese are extracted. This process is followed by precise chlorine dosing, after which the freshly treated water is ready for distribution.

Significant projects

Working alongside the United Utilities’ Wybersley team since the mid 1990s, Denca has carried out a number of significant projects at the High Lane site. These projects have been in addition to the provision of highly reliable 24/7 service and support on-site.

Resulting from an intimate knowledge of the water treatment works and United Utilities’ policy of good corporate governance, many of Denca’s solutions have provided additional process benefits as well as offering considerable cost savings.

During their relationship with United Utilities at Wybersley, projects undertaken by Denca have included:

Continuous monitoring capability for cryptosporidium contamination

At the time of this upgrade, Wybersley operated a multiplex turbidity system – a single analyser reading multiple streams. The solution involved the continuous monitoring of filtrate quality off the primary filters for turbidity measuring. Denca has integrated changes within the existing control system in order to meet the requirement and also incorporated a solution to ensure quality monitoring would still be available in the event of power failure.

Control systems upgrades – dual redundancy system

Concerned that a single PLC failure would cause a total shutdown of the works, and wanting to improve the reliability of their existing PLCs, United Utilities invited Denca to undertake a comprehensive technical survey with the remit to propose how reliability concerns could be eliminated or greatly improved.

Denca’s solution for this enabled the technically complex PLC controls to be translated into a reliable, expandable, proposal that was developed, then implemented on line and made fully operational, requiring only one plant outage, contained within a two-hour window – the maximum permissible interruption to the UU client water supply.

Denca’s expertise enabled the combination of the WTW’s PLC1 and PLC2 into a pair of hot standby units in order to create a ‘dual redundancy system’, thus ensuring that drinking water supply would not be compromised in the event of a single systems failure.

This Denca solution proved significantly more cost-effective than the creation of a ‘separate stream’ PLC system that had also been considered and included the creation of totally cohesive reporting of all process chemistry via the plant’s main SCADA system.

Implementation of Woodford Bore Hole

This project involved the introduction of a supplementary raw, hardened water source for additional supply to the Wybersley inlet during drought periods. During a 13-week window, Denca oversaw the introduction of chemical dosing and integration of all control systems.

Coagulation plant failsafe

Upholding a policy of sound risk management, United Utilities is committed to detecting failure of the water treatment works coagulation process in order to prevent uncoagulated water entering the water-supply network.

Working in association with United Utilities, and having already built-in a range of plant failsafe solutions at Wybersley, Denca developed a system enabling the monitoring of potential coagulation failure, with associated alarms and shutdowns in order to prevent contamination of water supply.

Integration of Lamella plant and SCADA upgrade

The requirement for Lamella facilities at UK water treatment works was instigated as a result of a DWR directive regarding the ‘potential’ risk of recycling water-borne bacteria into a WTW wash-water system.

The Lamella plant at Wybersley was commissioned in 2007. As part of the integration process, Denca also upgraded the Wybersley SCADA system to WinCC, a process involving the incorporation of over 700 control screens. By integrating the new Lamella plant into the existing SCADA, Denca avoided the creation of additional, unnecessary, PLCs.

Considerable knowledge

Adds United Utilities’ Senior Technical Officer, Kevin Allen, “As a result of their considerable knowledge, Denca are able to carry out all works according to plan without any failures. Denca has gained an enviable reputation across United Utilities as being total solutions providers, supported by wholly reliable and comprehensive back-up.

“Following one year of detailed development the extremely smooth SCADA change-over which was completed in just two days, during the commissioning of the Lamella plant demonstrates the level of careful planning and service we have come to expect from Denca”.

Collaborative working at its very best

“As with all other projects,” he continued, “we worked successfully as a team to present collaborative working at its very best. This was one of the smoothest projects we have ever completed. Not just for Denca, but right across United Utilities.”

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