MechChem Africa talks to Bennie Thiart, general manager for Grundfos’ Southern African region, about the company’s iSolutions offering, including smart pumps and dosing systems for water treatment, and the company’s ongoing success at the Nooitgedacht Water Treatment Works in Nelson Mandela Bay.
With dedicated regional offices in Kenya to service the East African region, Nigeria for West Africa and Johannesburg for Southern Africa, Grundfos has restructured in recent years to take full advantage of the growing need for water infrastructure across Africa. “As well the three dedicated African regions, we have also introduced three different business sectors – Building Services, Industry and Water Utilities – which we feel enable us to comprehensively cover the continent’s most urgent needs,” says Thiart.
“Water treatment is an application that bridges all these segments, including the building sector. Globally, Grundfos develops solutions for treating the water in storage tanks on top of buildings, for example, to neutralise bacteria such as legionella, which causes Legionnaires’ disease in buildings, particularly hospitals.”
On the industrial side, he continues, the food and beverage sector is a key industry, where additional treatment is required before water can be used for food processing. “In Africa we often treat ground water, which has to be fully disinfected if being used directly in food and beverage production. But there are other applications too, such as clean in place (CIP) that has different water quality standards.
“In some cases where deep borehole water is available, the water is already very pure and not much needs to be done, but quality monitoring in some form or another is always required to ensure that any water entering the closed circuit inside the plant is fit for purpose,” he points out.
In SA, however, Grundfos’ biggest market involves municipal water treatment. “Together with our key partners, we assist water boards with design, supply and installation of customised dosing and disinfection solutions on their water treatment plants. The Nooitgedacht Water Treatment Plant is an example of this. We can supply various solutions including transfer pumps, mixers, dosing and disinfection systems as well as control equipment with multiple communication protocols required in these plants to link our equipment to the operating system,” Thiart tells MechChem Africa.
Dosing success at Nooitgedacht
Describing Grundfos’ collaborated success with key water treatment partner, Aquatechnica, on dosing and disinfection solutions for the Nooitgedacht Water Treatment facility for Nelson Mandela Bay, he says that all Grundfos solutions are bespoke designs that depend on the water treatment process for the specific feed water characteristics and the output quality requirements. General treatment steps include coagulation, flocculation, sedimentation, filtration and disinfection. “Different dosing solutions are needed at various stages of the treatment process, depending on the water quality that comes in; this makes every plant unique,” he adds.
The Nooitgedacht scheme treats water from the Gariep Dam on the Free State-Eastern Cape border. The water flows via the Orange-Fish River tunnel and a series of connected rivers, from where it is piped, via the treatment works, to areas including Port Elizabeth and Nelson Mandela Bay.
Thiart says that traditional mechanical dosing involves using dosing pumps with manually adjusted cams to measure out known quantities of an additive. This type of pump has a turn down ratio of only 10:1, while if operated via a motor with a variable speed drive (VSD), a turn down ratio of around 100:1 can be achieved.
“By using stepper-motor technology in our new Grundfos advanced SMART Digital XL dosing pumps from our iSolutions range, we are able to offer turn down ratios of
1 000:1 and up to 3 000:1 on certain models. The SMART XL range also expands our dosing capacity from 30 ℓ/hr to 200 ℓ/hr with the latest release,” he notes. This makes the dosing accuracy of these pumps between 100 and 300 times better than standard cam-driven solutions,” he estimates.
In addition to their accuracy, integrated flow monitors in each dosing pump provide feedback about the actual flow in comparison to the set point, which is used to continually adjust the stepper motor rate to maintain dosing accuracy.
At Nooitgedacht, 16 DDA60-10 FCM SMART Digital XL dosing pumps were installed in a duty/standby arrangement with eight systems active at any time. These are plug-and-pump dosing systems that are expertly designed, aptly equipped and easily wall mountable.
The solution also included 16 Grundfos communication interface units (CIUs), which enable plug-and-pump communication between the PLC and pumps via Modbus TCP – and Grundfos CIUs offer communication options via many different protocols.
Also incorporated into the system is AutoFlowAdapt, which is able to compensate for environmental changes so the required target flow rate, smart chemical management and required water quality are always achieved. In principle, AutoFlowAdapt automatically and continuously compensates for fluctuating system pressure to ensure dosing accuracy is maintained.
“Digital control gives these devices the ability to add treatment doses in really fine and very accurate increments. It means our systems can now accommodate a wide range of treatment needs, while quickly responding to changes in the input water quality,” Thiart notes.
“Many years ago one of my mentors told me, in Afrikaans, that om te meet is om te weet which means ‘to measure is to know’. This is what modern digital dosing pumps bring to our systems.
Digital measurement technology enables us to control our dosing processes much more accurately, to produce a consistent treatment process and output stream of water at the precise quality required,” he tells MechChem Africa.
Pump solutions for water transfer
Also newly released as part of the iSolutions initiative are the redesigned extra-large versions of Grundfos’ CR vertical inline multistage pumps, which have been delivering best-in-class reliability and efficiency for more than 45 years.
“The new CR XL range’s improved design combines hydraulic efficiency with high efficiency IE3 motors to deliver improved performance, making these pumps ideal for use in water treatment plants and pressure boosting stations. The CR XL range can deliver flows from 80 m³/h to 200 m³/h per pump,” he says.
Larger vertical spindle pumps are an ideal substitute where larger flow capacities previously meant only end-suction or split casing pumps could be used. “At the top of the range are our CRE pumps with integrated frequency drives that can accurately regulate performance for constant pressure of flow solutions in pump systems,” Thiart explains.
Multistage vertical spindle pumps are superior to end-suction pumps on the maintenance side, too. A seal on a small CR pump can be changed in under a minute, while for the largest, it might take three minutes more. A vertical design also minimises plant footprint, which reduces the infrastructure required on the ground. And several pumps can be combined in parallel as a booster set to enable larger flows to be accommodated without sacrificing efficiency or flow/pressure control accuracy.
Grundfos MPC booster sets for water treatment transfer pump stations typically consist of three or four CR 155s on a common base frame, complete with parallel manifolds, valves and pressure sensors connected to a control cabinet with MPC controls. Such a station could supply 300 to 400 m3/h, without compromising pressure sustaining or flow characteristics required by the system.
“For high flow application we can also supply large multiple pump solutions of up to six pumps, and each pump will only run at the speed required to meet demand. In the middle of the night, only one pump might be running at half speed. As people wake up and water demand increases, this pump will first speed up until it reaches its best efficiency point, then a second pump will kick in and ramp up, then a third, and so on, until as many pumps as necessary are running. Most systems include a standby pump to accommodate maintenance requirements. This is permanently connected to the system so it can be switched on in an instant should another pump need to be taken offline,” Thiart explains.
The Grundfos CRE pumps and booster sets offer up to 40% energy savings compared to conventional end suction solutions running at full speed. In addition, maintenance on these units is easy as the majority of pump components are made from stainless steel to reduce corrosion problems and significantly extend pump life. “Because the motor is mounted above the pump, access to the seal and the wet-end components is relatively easy – at eye level on the larger pumps.”
“When a pump’s efficiency starts to drop, which we can monitor remotely via our GRM systems, we can schedule an on-site service that can, in most cases, quickly and easily return the pump to its original efficiency – and this can be done while the pump is installed at a pump station.”“With respect to manufacturing, we rely on local manufacturers for our base plates and pipework and we assemble entire pump system locally at our assembly facilities. We then deliver modular plug-and-play systems that have already been assembled and tested, to site.
“And by adding GRM and service level agreements (SLAs) to an installation, treatment plant and booster pump station operators can be sure that the system’s condition and performance is being constantly monitored for potential problems and that we at Grundfos will be on hand to intervene should any potential problems emerge,” Thiart concludes.