WATER & WASTE TREATMENT
PUMPS COPE WITH CORROSIVE CHEMICALS
Qdos pumps, from Watson-Marlow Fluid Technology Solutions (WMFTS), have cut maintenance downtime for dosing corrosive ferric chloride at Saur’s water treatment plant
aur has replaced faulty diaphragm pumps with cost-saving Qdos chemical metering and dosing pumps from Watson-Marlow Fluid Technology Solutions (WMFTS) for dosing ferric chloride at one of its water treatment plants in Normandy, France.
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Ferric chloride, used for coagulation in the water treatment process, damaged diaphragm pumps and resulted in maintenance downtime for Saur. The company, which supplies drinking water as well as wastewater treatment for industry and local authorities, used diaphragm pumps to dose ferric chloride (FeCl3) at its water purification plant in the Orne basin of Caen, one of the largest plants in Normandy. Commissioned in December 2016, the plant operates seven days a week, 20 hours a day, and is fully automated. It treats around 30,000m3
of water a day to
supply nearly 130,000 customers with drinking water.
Treatment of the water, which comes from the Orne river, includes clarification, disinfection, sand filtration, ultrafiltration and refining. The process requires injections of essential reagents such as FeCl3 to coagulate impurities, lime to soften the water, soda to rebalance the pH and bleach for disinfection.
When the plant began to operate, diaphragm and valve pumps were installed to dose FeCl3. This heavy, aggressive chemical regularly caused technical problems by attacking components of the dosing units, such as pumps, valves, pulsation dampers, check valves, back pressure and safety valves, and flowmeters.
22 MARCH 2025 | PROCESS & CONTROL
Gilles Garcia, Head of Drinking Water Production for the Caennais Basin at Saur’s Orne plant, said: “The existing equipment was not fully suited to dosing ferric chloride, which is a corrosive coagulant. The diaphragm and valve pumps required intensive maintenance, and in particular the diaphragms had to be replaced every three months or so. These regular and tedious operations, which involved removing the pump to gain access to the diaphragm, created leakage risks of the corrosive fluid and contributed to the premature aging of the equipment. We were therefore looking for a pump technology that did not come into contact with the fluid and required as little maintenance as possible.”
It was decided to replace the diaphragm pumps with Qdos chemical metering and dosing pumps from WMFTS in 2021. Qdos
peristaltic pumps offer a reliable alternative to diaphragm pumps: their patented ReNu pumphead can be quickly dismantled and replaced without tools and requires no maintenance or specialist training for operators. In addition, Qdos has an integrated leak detection system that reduces losses and avoids operator contact with corrosive chemicals like ferric chloride. The Qdos pumps dosed 426,000l at a back pressure between 2 and 3bar for 8,600 working hours before requiring any maintenance for Saur. Operating on average 20 hours a day, the Qdos 120 pump did not require any intervention in the first year, a first for this installation compared to the diaphragm pumps.
Alexandre Marnay, Sales Engineer at Watson-Marlow Fluid Technology Solutions, said: “Our pumps provide peace of mind because, in the event of a failure, repairs can be carried out quickly, easily and much more safely than with diaphragm and valve pump technologies, which require contact with the chemical product. The first Watson-Marlow pump to be installed at the Orne plant was for chlorination, as this requires a low, precise flow rate. Since the introduction of Qdos pumps, various models of Watson-Marlow pumps have been deployed at the plant for the bleach, soda and sulphuric acid injection processes, and for polymer flocculation. After three years of using Qdos pumps, Saur is happy with the performance of the pumps. Garcia said: “The Orne plant is equipped with a total of around 50 dosing pumps. Watson-Marlow has provided us with an operating table showing that operating costs are lower. The extra cost of materials is paid off in three years. Furthermore, we went from diaphragm pumps that consume 0.75kWh to Qdos pumps that consume 0.20kWh, so we're reducing our energy consumption by three.
“Alexandre Marnay is easy to contact and is close by so he can help at short notice, which is a real plus for us. A physical presence rather than a telephone call is essential for operators, because we can't possibly know the subtleties of each of the many pieces of equipment in place at the plant. The diagnosis, advice and expertise that the technician brings to us on site enhances the quality of our operations.” Saur’s experience with Qdos chemical metering and dosing pumps has prompted it to invest in three Qdos H-FLO pumps, which suit higher flow rates up to 600l/h and pressures of up to 7 bar (102 psi).
WMFTS
www.wmfts.com
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