SPECIAL WORKS
to equalise flow rates within the three ASP lanes so that treatment efficiency and capacity would be improved. This was achieved, but as Josh says: “The penstock control system worked extremely well. By adopting a scheme based on cross-correlation flow measurement for both the relief pipe and the ASP channels, we were able to avoid substantial civil works, which delivered dramatic financial cost and carbon savings, as well as almost no interruption to the operation of the plant.”
MMB has estimated that a conventional build solution involving modification of the channels with a new distribution chamber would have taken around 8 months and cost in excess of £4.5 million. In stark contrast, MMB’s solution, outlined above, was delivered at a cost of around £1 million.
As a Capital Delivery Partner and part of the Welsh Water Alliance, under the terms of its contract, MMB’s cost savings at Five Fords deliver financial benefits to both MMB and Dŵr Cymru Welsh Water. Consequently, the water company’s customers also benefit.
Looking forward
Nivus NF750 Transmitter in IP68 field enclosure
A key advantage of this method is its ability to operate effectively in the most demanding and heavily polluted applications. Influencing factors such as flume shape, discharge behaviour and wall roughness are all accommodated within the flow computation.
Initial results
The NIVUS flowmeters were installed before the penstock solution was implemented, so that flow variation could be observed both before and after the penstock installation. However, local engineers raised concerns about the potential for the penstocks going from fully open to a closed position too quickly or not opening quickly enough
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during a surge, causing backup in the channel. In addition, there were concerns that the penstocks might react too quickly causing intermittently variable flow rates.
“Happily, none of the initial concerns materialised,” Josh explains. “With the ability to optimise the ‘nudge and wait’ period, it became possible to ensure a smooth flow with an even split between the ASP lanes. As a result, the scheme sailed through the 28-day proving phase with no issues reported, and has performed problem-free for several months since that time.”
Key scheme outcomes The overall objective of the scheme was
| February 2025 |
draintraderltd.com
MMB staff have been so impressed with the results of this project that they have since organised internal webinars with engineering colleagues from all over the world, explaining how they too can implement this technology to deliver cost and sustainability benefits.
The NIVUS cross-correlation flow measurement technology will be rolled out to future wastewater projects. However, it is also applicable to other applications such as pump management under AMP8, as well as in-pipe potable water flow measurement applications.
Summarising, Josh Sparks says: “The physical constraints at Five Fords forced us to widen our search for potential solutions, and we have obviously been delighted with the results. Cross- correlation flow measurement turned out to be the key that unlocked the financial, time and carbon savings that have been achieved, and we look forward to delivering similar benefits on future projects.”
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