The ‘Sobye’ self-cleaning belt filter from Jacopa’s Swedish manufacturing partner, Nordic Water, provides an automatic, compact solution for primary treatment to replace settlement tanks. The filter has recently undergone extremely successful trials at a unique Scottish Water test facility demonstrating excellent process performance and proving the effectiveness of the system.
The utility’s Waste Water Test Centre is the first facility of its kind in the UK and is one of two research hubs operated by its commercial subsidiary Scottish Water Horizons. The site offers real-life testing of new technologies, processes and equipment under live conditions, with the aim of accelerating technology and adoption.
The centre, near Falkirk, is sited next to Scottish Water’s existing operational waste water treatment works and was transformed from a redundant sludge treatment building. The facility’s testing hall provides three individual feeds of waste water from different stages in the treatment process so that solutions that target the various stages of the treatment process can be trialled. The waste water discharged from the testing area then enters back into the normal treatment process, providing a safe and dynamic testing environment to upscale experimentation.
At the trial site, on the Firth of Forth, Jacopa’s testing was undertaken at the Waste Water Development Centre on a dedicated inlet receiving a continuous stream of live, screened effluent on a large scale. The influent from the waste water treatment plant’s inlet works entered the Sobye filter and following treatment by the filter, primary treated effluent was returned to the downstream plant treatment processes.
Jacopa worked closely with Scottish Water to conduct testing under a number of different scenarios (eg. high/medium/low flow rates). Samples were also taken and analysed on a daily basis by the utility to prove the effectiveness of Jacopa’s system.
All relevant parameters were tested over the five-week period, such as solids retention and effluent characteristics, using the site’s comprehensive monitoring equipment; the results are reported to be extremely impressive and can be obtained by contacting Jacopa direct. Another welcome outcome is that an order has also been placed for Jacopa to refurbish the grit plant at the main treatment works.
The Sobye factory-built, small footprint primary treatment process is designed to remove solids and particles from wastewater. It is intended to replace the need for the usual space-taking settlement tanks found at wastewater treatment plants, reducing both footprint and costs – due to its effectiveness, it can offer savings of up to 50% on investment.
The Sobye filter has acquired an excellent reputation over a 25 year period since its initial development in Norway then Sweden and more than 200 systems are currently in use, with around 100 in the municipal primary treatment market. The system takes screened, municipal wastewater from the inlet works and this then flows under gravity through the moving robust filter belt with filtered wastewater being discharged from the bottom of the tank. The belt speed is controlled to allow a layer of sludge to build up on the belt which increases filtration efficiency.
The Sobye-filter belt is incorporated into a cassette that can be easily removed from the filter tank for maintenance and repair. The belt is made of polyester, which ensures an exceptionally long operating life cycle.
When the screen needs to be cleaned the belt rotates, and particles are removed by an integrated brush. Next, a high-pressure spray bar cleans the belt, which is quicker and cheaper than air cleaning, and the dislodged sludge is discharged to a conveyor for washing and pressing to a high dry solids content. The washwater, along with the filtrate from the press, is returned upstream. The filter belt is extremely robust and is easily replaced when required.
Because the Sobye filter uses the integrated brush to clean the filter fabric, no compressor or pump is required. The filter also has an exceptionally high filtering capacity compared to its small size and is therefore an excellent choice where space is limited.
There are three sizes of belt filter for use in the municipal wastewater market: the Sobye TD 07, the TD 14 and the TD 20. These all have an excellent reputation as small-footprint units with a high filtering capacity: their effective filter areas are 0.74m2, 1.45m2 and 2.0m2 respectively.
The units are made in stainless steel, with a heavy-duty polyester belt mesh aperture size ranging from 60-1,000 microns. Flow volumes are up to 50m3/h for the TD-07, 100m3/h for the TD 14 and 150m3/h for the TD 20.
The effectiveness of BOD and suspended solids removal across the Sobye unit is at least equivalent to conventional primary settlement but with the greatly reduced footprint discussed above. Operational and maintenance costs are also similar to those of conventional primary settlement tanks and scraper systems.
Key features and benefits include the high efficiency belt filter and the solids removal design basis, which (as seen in the figure) is equal to an 11m diameter primary settlement tank and with hydraulic loading design equal to a 7.5m diameter primary settlement tank.
The Sobye solution offers at least equivalent process performance, a smaller footprint, modular and factory build off-site, lower whole life cost, reduced carbon footprint, shorter delivery times, and minimised site health and safety risks compared to the construction, operation and maintenance of conventional primary settlement tanks.
The system can be deployed as a temporary treatment solution and produces high quality sludge and readily-verified performance. The Sobye belt filter can additionally be retrofitted easily into existing facilities, as it is simple to install. Jacopa envisages that given the speed and ease of implementation it will also be embraced as an effective permanent treatment system, with the option for rental where shorter-term challenges to efficient operation exist due to works overload or where maintenance of primary tanks is a concern for operators.
The Sobye belt filter was the focus of a recent industry presentation by Joakim Nilsson of Jacopa’s Swedish manufacturing partner, Nordic Water. Joakim presented the case for this advanced process versus conventional civil works settlement tanks, reviewing quality, standardisation and safety and evaluating performance including suspended solids removal, sludge production volume and footprint benefits.
Nilsson emphasised that while existing primary treatment practice is predictable, scalable, and normally robust, nevertheless high loads, inlet works failures and scum can pose significant issues, and repair and maintenance can be hazardous. He produced data showing the superior performance in both biochemical oxygen demand (BOD) and total suspended solids (TSS) removal, highlighted the 6-8% dry solids produced and showed that the sludge had a higher calorific value product. He also provided an overview of the performance and estimated costs associated with each filter in the range.
In summary, he concluded that the Sobye filter provides at least equivalent process performance to primary settlement tanks, with a far smaller footprint. The filter is also modular and factory-built offsite, and offers lower whole life costs, a reduced carbon footprint, and shorter delivery times. The filter also minimises related site health and safety risks.
Jacopa Managing Director, Alex Lloyd, said, “We have been extremely pleased with our collaboration with Scottish Water and by the reliable operation of the Sobye filter and results of the tests, which underlined the effectiveness of the Sobye filter as a replacement for standard primary settlement tanks. On sites where space is at a premium and customers seek tangible innovative solutions to reduce costs, we envisage there will be considerable interest in Sobye.”
Rebecca Skuce, Project Manager at the Development Centre, said, “We were delighted to work alongside Jacopa to help facilitate this trial. The positive results from the trial are very exciting and we’re privileged that our test facility has helped Jacopa achieve their desired outcome. Bringing bold new solutions to market will significantly enhance how we ensure our environment is safeguarded and help us secure a more sustainable future.”