A water recycling installation driven by WEG motors
The project to expand a wastewater treatment plant south of Johannesburg, undertaken by water purification specialist PCI Africa, has included the installation of 65 WEG motors.
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 demand that the region’s wastewater treatment facilities continue to increase their capacity.
According to PCI Africa proposals manager Lebo Rathebe, the mechanical portion of the contract included the inlet works, 25-m-diameter primary settling tanks (PSTs), 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,” says Rathebe. “The PSTs were fitted with 30-m-long half bridges and two recycle pumps per tank.”
The new module treats water using a three-stage process for the biological removal of nitrogen and phosphorous, he explains. 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,” he says. “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, says Zest WEG sector specialist for public sector business development Dillon Govender.
The motors on this site range mainly from 30 kW to 90 kW flange-mounted units and also include pad foot-mounted motors from 1.5 kW to 37 kW.
“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,” says 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. He highlights 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 says. “The contract also specified the inclusion of anti-condensation heaters for all motors of 4 kW and above. Our motors on site also boast paint plan 212P as well as IP66 ingress protection to help keep them free of moisture or dust.”
Zest WEG supplied its IE3 top premium efficiency motors to satisfy the client’s specifications and to help achieve the lowest cost of ownership. Govender notes that the company offers a five-year guarantee and also supplies IE4 motors – said to be the next level of efficiency.