The existing old pumps were prone to tripping and often flooded the pump station, so the first step of the project saw Veolia cleaning the pumping station, situated 15 metres below ground. This included removing sump, scraping the walls and rehabilitating the existing infrastructure for the new, larger pumps.
Veolia replaced the aged pumps with two new Sulzer pumps, imported from Germany, that were integrated into the existing pipework infrastructure. Sulzer is one of the Veolia Group’s international strategic suppliers for pumps. The two immersible Sulzer XFP high-capacity sump pumps are capable of processing 220 litres of raw sewage per second at a 27 metre elevation.
“The pumps are set at a standby duty configuration to ensure system reliability. This means that when the first pump reaches 60% capacity, the second pump will automatically switch-on to ensure demand is met and that no flooding or overflow discharge occurs,” comments Blake Cooley, Project Engineer, Veolia Water Technologies, South Africa. “In addition this standby configuration also ensures that if either pump malfunctions or requires servicing, it gives the pumping station a four to eight hour buffer period before breakdown or overflow.” These Sulzer pumps, however, would continue to operate in the unlikely case of overflow due to their submersible designs.
Early in the installation, the existing pumps failed and flooded the entire pumping station. In addition to cleaning the waste, Veolia installed a temporary T8 pump to ensure that no effluent would be discharged during the installation period. “As this was a live operation, we had to bypass the Ncandu pump station using a temporary solution so that the pumping of the sewage to the wastewater plant could continue,” comments Cooley.
To ensure the maintainability of the pump station, Veolia installed a penstock stainless steel gate to effectively isolate the pumps from each other. This means that when one pump requires cleaning or maintenance, the gate will isolate the sewage flow to the functioning pump only. Prior to this, the operators relied on manually handled sand bags which proved extremely laborious and often ineffective.
In order to power the two 71 kW pumps, Veolia was also contracted to upgrade the transformer and Motor Control Centre (MCC) panels with the help of external instrumentation and control suppliers. “These MCCs provide variable speed and soft-starting pump performance ensuring that their operating capacity matches the sewage demand of the time,” adds Cooley. These intelligent systems will also immediately alert the operator, via SMS, to any potential pump tripping or overloading. Veolia also installed a precautionary one-kilometre air raid siren to alert the operator of pump station overload or failure.
“These safety systems, in addition to our operator training on MCC usage and proper maintenance practices, aim to reduce the chances of any sewage discharge from this pump station in the future,” concludes Cooley.
Veolia repaired and refurbished the existing T6 pumps and returned them to the Newcastle Municipality where they can function in lower-capacity applications. The revamped Ncandu pump station was also designed to accommodate future growth and Veolia completed the required pipework for additional sump pumps as well as made space provisions for a new generator room.
Veolia was contacted for this pump station upgrade in January 2016 and handed the station over to Newcastle Municipality later that year. The company is currently upgrading pump stations across South Africa, with recent completed projects in Gauteng, Eastern Cape and the Free State.