Water & Wastewater Treatment Magazine
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Project focus: water treatment m 3 per hour. The project presented a number of construction challenges as a result of heavy clay soils which impacted on the site works but the simplicity of the CarboPlus process allowed the technology to be fully constructed and tested within the original construction programme of 17 months. The improvement works saw the building of a new process stream and the rehabilitation of the old one by replacing the existing GAC filters with three CarboPlus filters. The building of the new process stream (2 Delreb, 4 CarboPlus and 6 sand filters) resulted in an increased flow from 52000m 3 /d to 75000m 3 /d. The improvement works also included provision of a new UV plant for the new and refurbished streams. There was no interruption to production during the construction period and all client performance and quality objectives were met. The total project investment, including 2 Delreb (high rate clarifiers used to remove the suspended solids), 7 CarboPlus, 6 sand filters and 4 UV reactors was in the region of 25 million euros. Efficiency improvements The technology has delivered efficiency improvements as well as pollution reduction. The CarboPlus technology used was selected primarily for its effectiveness in pesticide removal. However the process was also cost efficient due to its small total footprint of only 300 m². The technology used at Basse-Goulaine has been refined through the use of the micro granular Activated Carbon. This has generated additional efficiencies through the ability to capture and reactivate the media to reduce operating costs further, as well as negating the need for any chemicals dosage. Other efficiencies realised on the project when building the complete process stream was the construction as a single connected process with clarifier, CarboPlus and final sand filter within a single building. Stephanie Piel, Saur's R&D engineer on site, appreciates the benefits of the new CarboPlus process. "CarboPlus works by ensuring a continuous dosage of activated carbon, so that an adequate quantity of new and fresh activated carbon always exists in the reactor, which in turn ensures consistent efficiency of the carbon fluidised bed," says Piel. "As the reactor now contains a larger amount of activated carbon compared to other solutions, it means the process is more efficient because there is a higher concentration and larger exchange surface to capture the pollutants." The technology also brings added efficiency as doses of carbon can be adjusted for peak periods. In Basse-Goulaine, where quantities of metaldehyde peak in the winter with more intensive farming practices, the treatment dose is adjusted every season, to follow this trend. In less than six months since its introduction, the technology has also produced some encouraging results. The CarboPlus technology was introduced to treat all water flow through the plant. Early results show a decrease in pesticide levels to well below regulatory limits of 0.5µG/L for total pesticides, and below 0.1µG/L for metaldehyde, from a raw water metaldehyde concentration of 0.32 µG/L observed during winter pollution peak before the installation. In-depth results and analysis of the CarboPlus patented technology have been published in scientific articles over the last two years, including by INRA (France's top agricultural research institute), the CNRS (French National Centre for Scientific Research) and the École des Ponts-ParisTech graduate school. This independent research confirms the assertion of Saur Group's Head of R&D Fabrice Nauleau, who says: "Adsorption using activated carbon is the only technique that removes micropollutants. We have a duty, as a professional provider of water services, to respond to the questions asked by our clients and the trends emerging as a result of customer needs. That pushes us to find solutions that don't just work but that go beyond current legislation so they stand the test of time". More information is available at saurglasgow.com/saur-worldwide/ carboplus ● Replacement of GAC filters with CarboPlus patented technology ● New process stream featuring Delreb, CarboPlus and sand filters ●New UV plant for both new and refurbished streams • Innovations A diagram showing the workings of the CarboPlus technology 28 | APRIL 2017 | WWT | www.wwtonline.co.uk