Hydro International’s cuts Opex costs and carbon footprint at Carbarns WwTW

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 6 mm fine inlet screens at Carbarns WwTW were failing regularly as the plastic screen panels were very prone to breaking, particularly following storm events when flows were higher and contained more debris.

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. Normally sewage sludge was sent directly to the Daldowie fuel plant to be processed 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, the sewage sludge first had to be tankered to Shieldhall WwTW, some 20 miles away, for further processing, before being pumped over to Daldowie. With up to 23 tankers a week transporting sludge, the associated costs were considerable.

Scottish Water worked with Hydro International’s UK Wastewater Services team, M&N, to find a solution. The team installed a Kuhn KHU-S Multirake Boomerang 70mm screen to remove coarse screenings and protect the two FSM FRS111 escalator screens which provide fine screening.  The FSM screens were fitted at 60°, giving an impressive maximum flow capacity of 770 l/s each.

Each of the screens has capacity to take the full flow to treatment, should one need to be taken off-line for maintenance or repair, and the screen panels are stainless steel so able to withstand storm flows. A launder system was installed to transport rag to two Kuhn KWP-HD 400/1200 wash presses to process, wash and compact the rags.

Simon Light, National Sales Manager for Hydro International, said, “We needed to find an effective solution 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 combining 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.”

The UK Wastewater Services team will service the screens every year and provide maintenance to ensure the equipment is operating at optimum performance.

Learn more about how our inlet works specialists can help you with your wastewater needs, visit hydro-int.com/ukwws.