Hatch – Midmar Water Treatment Works Upgrade, Howick

WINNER COMMENDATION Hatch for Midmar Water Treatment Works Upgrade, Howick

Located in Howick, the Midmar Water Treatment Plant (WTP) is owned and operated by Umgeni Water. The plant treats raw water from Midmar Dam, which is located on the upper Umgeni River system.

The WTP supplies water to Howick and Mpophomeni, most of the south-western and southern suburbs of Pietermaritzburg, Greater Edendale, Vulindlela, Thornville, Hopewell, Richmond and the Umlaas Road node. It also serves eThekwini’s Outer West area (including the areas of Cato Ridge, Georgedale, Gillitts and Hillcrest), as well as consumers on the Lion Park and Eston-Umbumbulu pipelines from the Umlaas Road node. The supply area has recently been extended via eThekwini’s Western Aqueduct.

The Midmar Water Treatment Plant was upgraded from a design operating capacity

of 250 Mℓ/day to 395 Mℓ/day on a raw water intake basis. The plant utilises chemical dosing, super pulsators and rapid gravity sand filters, with disinfection using chlorine gas for the production of 375 Mℓ/day of potable water.

The project required upgrades to the chemical dosing system, an additional new super pulsator clarifier and six new rapid gravity sand filters at the main water treatment works, as well as a new backwash water recovery tank, two new clariflocculators and a gravity thickener at the sludge treatment works, with associated mechanical, electrical, control and instrumentation upgrades and integration.

Hatch was awarded the professional services contract for the design, construction monitoring and commissioning, with construction commencing in May 2015 and completed by June 2019.

PROJECT TEAM Client: Umgeni Water Consulting engineer: Hatch Main contractor: Icon Construction

Safety enhancements included the addition of ventilation equipment to the filter gallery, as well as structural modifications around the filter syphon valves. In turn, the addition of a second backwash water balancing tank ensures improved recovery of wash water, enhancing the overall efficiency of the treatment system and the quality of water returned to the natural environment.

The emergency chlorine scrubber (ECS) design was subjected to critical design reviews to ensure that it met major hazardous installation and client safety requirements. The ECS is believed to be the largest of its type in South Africa.