Motion Control & Drives

WEG motors power wastewater plant

April 2022 Motion Control & Drives

Water purification specialist, PCI Africa, has expanded the treatment capacity of a wastewater plant south of Johannesburg, installing over 65 WEG motors for optimal performance, reliability and energy efficiency. The project involved the addition of an extra module to the existing wastewater treatment plant, allowing it to treat another 50 000 cubic metres of water each day. Ongoing urban migration and development in the area have demanded that the region’s wastewater treatment facilities continue to increase their capacity.

According to Lebo Rathebe, proposals manager at PCI Africa, the mechanical portion of the contract included the inlet works, primary settling tanks (PSTs) 25 metres in diameter, a biological reactor, secondary settling tanks and dewatering facilities. “We added a sixth module to the plant, which included the installation of two screw pumps to feed the PSTs, with four front rake screens and hydro-conveyors,” Rathebe said. “The PSTs were fitted with 30 metre-long half-bridges and two recycle pumps per tank.”

WEG motors driving aerators at a wastewater plant.

The new module treats water using a three-stage process for the biological removal of nitrogen and phosphorous, he explained: “Influent – the incoming stream to the plant – first enters an anaerobic reactor before reaching an anoxic reactor and finally an aerobic reactor. Recycle pumps transfer part of the stream from the anoxic reactor back to the anaerobic reactor, to preserve microbiological matter and keep the solution homogenous. There are also recycle pumps to move some of the stream back from the aerobic reactor to the anoxic reactor.”

The WEG W22 motors supplied by Zest WEG for this project mainly power the numerous pumps on the site, as well as the mixers and agitators, according to Dillon Govender, Zest WEG’s sector specialist for public sector business development. The motors on this site mostly range from 30 kW to 90 kW flange-mounted units and also include pad foot-mounted motors from 1,5 kW to 37 kW.

A return-activated sludge pump station with power provided by WEG motors.

“WEG motors are installed in all major processes, from screening, de-gritting, primary settling biological nutrient removal reactors, secondary settling and waste sludge thickening up to dewatering,” said Govender. “Our role in this project demonstrates our growing contribution within the wastewater sector in South Africa and the continent generally.”

In this project, WEG motors are also driving the pumps for return-activated sludge and waste-activated sludge. Govender emphasised the demanding nature of wastewater applications, given the high levels of corrosion that can occur if equipment is not suitably designed and manufactured. “The Class H insulation on these WEG motors enhances their durability and lifespan, allowing them to withstand a higher temperature rise,” he explained. “The contract also specified the inclusion of anti-condensation heaters for all motors of 4 kW and above. Our motors on site also boast Painting Plan 212P as well as IP66 ingress protection to help keep them free of moisture or dust.”

With the rising cost of electricity, it was vital for the motors to run at high efficiencies to control the plant’s operating costs. Zest WEG supplied its IE3 premium-efficiency motors to satisfy the client’s specifications and ensure that the owner achieved the lowest possible cost of ownership.

Rathebe emphasised the advantage of having Zest WEG supply almost all the motors on the project, saying this made life easier for both the contractor and the end-user. “In terms of ongoing operation, the plant owner can economise on the spares they carry, and be assured of responsive after-sales support,” he said. “As the contractor executing this project, it was easier for us to have one source of responsibility when dealing with the supplier.”

Govender concluded by stating that the quality, robustness and efficiency of WEG motors allow Zest WEG to offer a five-year guarantee, giving customers not only value for money but peace of mind that operations will not be disrupted by unexpected stoppages.


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