Carbarns Wastewater Treatment Works (WwTW) is located in Wishaw, to the South-East of Glasgow, within the Clyde River valley. The site is part of the ‘Clyde 7’ group of Scottish Water treatment facilities, serving a population of over 54,000 from Wishaw and Overtown areas. Along with the inlet works, the site has primary and secondary treatment and phosphorous removal. Treated water from the plant is discharged into the River Clyde.

The 6mm fine inlet screens at Carbarns WwTW were failing regularly as the screen panels were plastic and very prone to breaking, particularly following storm events when flows were higher than usual and contained more debris. Scottish Water was having to stock spare panels on site and replace them as often as every week, depending on the weather.

When the inlet screens failed, a considerable amount of rag was feeding through to the primary settlement tanks, causing chokes in the sludge pumps. When the screens tripped out in storm conditions the bypass screen would blind up in minutes, not allowing enough time for standby operators to reach the site, and causing flooding at a nearby property. The result was a significant amount of time and resources spent on clearing these chokes and blockages and cleaning up by the operations team.

The biggest impact of this inlet issue was the financial and carbon implications. Carbarns WwTW would normally send sewage sludge directly to the Daldowie fuel plant, near Glasgow, which processes it into a renewable, low carbon form of biomass fuel pellet. However, because of the high content of rag in the sludge caused by the inlet screen failures, it could not be sent directly to Daldowie Fuel Plant but had to be taken for further processing to Shieldhall WwTW, some 20 miles away on the other side of Glasgow. This involved up to 23 tankers a week transporting the sludge to Shieldhall for additional treatment, before it could be pumped over to Daldowie. The associated costs of transporting the sludge to Shieldhall WwTW were considerable.

Scottish Water worked with Hydro International’s UK Wastewater Services team, M&N, to evaluate the site and propose a solution. The team installed a Kuhn KHU-S Multirake Boomerang 70mm coarse screen to provide protection to the FSM escalator screens by removing the larger coarse screenings. Two FSM FRS 111 escalator screens were then fitted at 60°, providing an impressive maximum flow capacity of 770 l/s each, to provide fine screening of the sewage inflow.

The screens are running in a duty standby mode, conducted automatically by the control panels which were supplied for all equipment. Each of the screens has capacity to take the full flow to treatment, should one need to be taken off-line for service, maintenance, or repair.  The strong screen panels are stainless steel so able to withstand storm flows, combatting the initial issue of weak plastic-based material screens. A launder system was installed to transport rag to two Kuhn KWP-HD 400/1200 wash presses to process, wash and compact the rags.

Once the new inlet works package was installed, the primary settlement tanks and aeration tanks were cleaned to ensure that no rag was left in the system.  This was an additional cost of £106K before Daldowrie Fuel Plant could accept the sludge again.

Simon Light, National Sales Manager for Hydro International, said:

“We needed to find a high-quality effective solution for the Carbarns WwTW to prevent any further overflows, and to help reduce the high cost and carbon impact the high content of rag in the sludge was creating. Our specialist inlet works team designed and installed a robust, reliable inlet works system that combines screening, washing, transport, compaction and dewatering in a single cost-effective and sustainable standalone solution.”

Stephen Heatley, WW Operations Team Leader at Scottish Water, comments:

“Knowing the team for over 20 years, we were confident that they would provide a solution that works exceptionally to meet our needs. Since the project’s completion in September 2020, there has been a significant reduction in costs and carbon use now that the sludge can be transported directly to Daldowie Fuel Plant for processing. The amount of reactive time that operation staff previously needed to spend dealing with chokes and cleaning up has dramatically reduced, with a knock-on effect that morale has improved, providing more time to spend on proactive tasks.”

Moving forward, the UK Wastewater Services team will service the screens every year and provide maintenance to ensure the equipment is operating at optimum performance. To learn more about how our inlet works specialists can help you with your wastewater needs, visit hydro-int.com/ukwws.

Thames Water’s Greenham Common Sewage Treatment Works (STW) is situated in the shadow of a former US Air Force base in Bishops Green, Newbury, and alongside the River Enborne. The untreated wastewater that Greenham Common receives has a high rag content and repeated screening carry over was affecting the full treatment process, the overall performance of the site and risked that the site would go out of environmental compliance.

Thames Water approached Hydro International’s UK Wastewater Services team, M&N, to evaluate the site and propose a robust solution. The team installed the MNSS Combined Screen, to capture larger influent materials at the front end of the wastewater treatment process, protecting and improving the efficiency of the downstream treatment system.

Due to the site hydraulics/flows, there was no reliable wash water system for the MNSS Combined Screen, so the team found an innovative way to solve this. They created a bespoke system, including pumps, to use the effluent from the site’s primary settlement tank. The spray nozzles on the MNSS Combined Screen were also altered to accommodate the change.

Simon Brum, Project Manager, Hydro International’s UK Wastewater Services Team, said:

"We needed to find a quick and effective solution for the Greenham Common STW to prevent any overflows, and designed and installed a robust, reliable inlet works system that combines screening, washing, transport, compaction and dewatering in a single cost-effective standalone solution.”

Henry Crompton, Lead Project Engineer at Thames Water Utilities Ltd, commented:

“We needed a suitable solution that was effective and within budget, and the team delivered that. We are very happy with the work undertaken on this site and will be using it as an example to our other Thames Water teams who may encounter the same issues.”

Handling flows of up to 150 l/s, the MNSS Combined Screen is designed for smaller plants and those facilities that require a more cost-effective screening solution - helping engineers, operators, and site owners to maintain treatment effectiveness even at remote and budget - constrained sites.

Optimised for reduced maintenance and extended component lifetimes by the UK Wastewater Services team, only the MNSS Combined Screen achieves a screenings capture ratio of 53%, the highest of any independently tested 6mm combined screen.

To learn more about how Hydro International’s UK Wastewater Services team can help you with your wastewater needs, visit hydro-int.com/ukwws.

Suspended solids carried in water can cause a range of harmful effects in rivers, lakes and oceans, making the capture and removal of these solids critical for effective environmental protection. To address this problem, the project focused on optimising the stacked trays that remove high levels of suspended solids from wastewater.

Combining optimisation methods and computational fluid dynamics (CFD), the project was able to derive new designs for hydrodynamic solids removal components that would have been difficult or impossible to achieve using traditional engineering methods.

The research was part of a Knowledge Transfer Partnership (KTP), supported by the UK government’s innovation body Innovate UK, which began in July 2019 and ran until September 2021. It builds on years of collaboration between Hydro International and the University of Exeter in the field of CFD.

The core of the project involved the optimisation of stacked trays that enable the removal of high levels of suspended solids in wastewater, with the primary objectives being to improve performance and reduce maintenance requirements. This was a complex, multi-objective, high-dimensional problem, so the team needed to adopt an unconventional approach in order to solve it.

To tackle the problem the project team coupled Bayesian optimisation techniques and CFD modelling, using a Bayesian optimisation toolset originally developed by the world-renowned Machine Learning Group at the University of Exeter. Bayesian optimisation was selected as it can be an order of magnitude more efficient than alternative approaches, such as genetic algorithms, on such complex design problems.

The Bayesian optimisation toolset was then connected to CFD simulations, allowing the team to use computing power to automate the design and evaluation process. The team ran the CFD simulations using supercomputers in Exeter and Bristol, with each optimisation run modelling some 300 designs at a time. This would have been impossible to achieve using other optimisation techniques. The team was one of the first in the world to use these techniques on new GW4 Isambard supercomputing architectures,

The team subsequently corroborated simulation results through physical testing of prototypes in Hydro International’s hydraulics laboratory in Clevedon.

The outcome of the project was a new stacked tray design that improves grit removal performance and enables the production of more compact systems that can handle higher wastewater flows and requires less maintenance—an excellent example of combining academic research with commercial incentives to address real-world challenges.

Although the project was focused on improving technologies that will be applied to future iterations of the HeadCell® advanced grit removal system, the findings are fundamental to Hydro International’s core technologies, and will be applicable to other products that rely on the same hydrodynamic principles such as Downstream Defender^® and First Defense^®.

In addition, not only did the project apply methods for complex design optimisation already developed by the University of Exeter, but it also drove new developments in multi-objective optimisation and constraint handling, resulting in new advances in expertise and understanding.

Following completion of the project, Innovate UK assessed the KTP and awarded it a Grade A, or “Outstanding”.

Dan Jarman, Hydro International’s Group Technical Manager said:

“We have a long history of investing in new science and new technologies to help our customers, and this project continues that tradition. This is the first time that Bayesian optimisation and CFD techniques have been applied in the water sector, which represents a significant step forward in product design excellence. In a sector that has been unfairly criticised for being slow to adopt new technologies and techniques, we’ve shown that there are teams out there willing to push boundaries in order to benefit utilities, consumers and the environment.”

Jonathan Fieldsend, Professor in Computational Intelligence at the University of Exeter said:

“This project is an excellent example of what can be achieved when a KTP involves such a wide range of talent and experience. To achieve its outcome, it has needed academics from the Computer Science and Engineering departments, specialists from industry, and support from a highly-skilled impact and business team. It has delivered significant enhancements for an important Hydro International product - in the crucial area of wastewater management - and has also led to advances in applied optimisation techniques and algorithms which have use more broadly in CFD-driven design.”

Hydro International Ltd is a global company that provides advanced products, services and expertise to help municipal, industrial and construction customers to improve their water management processes, increase operational performance and reduce environmental impact.

With over 40 years of experience and a reputation for engineering excellence, businesses and public organisations all over the world rely on Hydro International products and services to reduce flood risk, improve water treatment and protect the environment from water pollution.

Headquartered in Clevedon, UK, Hydro International has a network of over 80 distribution partners and serves customers in more than 40 countries.

The University of Exeter combines world-class research with excellent student satisfaction, ranking in the Top 150 of the THE and QS World University Rankings. We are one of the very few universities to be both a member of the Russell Group and have a Gold award from the Teaching Excellence Framework (TEF), evidencing our international reputation for excellence in teaching and research.

Each year, the University of Exeter delivers over 1500 projects with industry and generates over £52m from this work. We believe impact is about making a difference, and our world-class researchers have an excellent track record in making valuable contributions to our society, economy and the environment.

Our dedicated KTP team - based at the University’s Innovation, Impact and Business directorate - is the leading Knowledge Base partner in South West England and has successfully delivered over 100 KTP projects to date, with 85% of these rated good to outstanding.