PHASE 5 – EXTENSIONS TO THE TEMBA WATER
SUPPLY SCHEME

The Temba Water Supply Scheme site is situated within the most Northern portion of the municipal area of the City of Tshwane Metropolitan Municipality, some fifty kilometers to the north of Pretoria’s Central Business District (CBD). The project site is simply accessed from the N1 Highway to Polokwane, from the Hammanskraal off-ramp.

The Phase 5 extensions of the Temba Water Treatment Works which were started in 2004, and completed in 2005, comprised the addition of a 30 Ml/day module to the existing four phases, which together also had a capacity of 30 Ml/day, thus extending the total capacity of the plant to 60 Ml/day.

The contract comprised the upgrading of the existing raw water Pumpstation situated below the Leeukraal Dam to the north of Hammanskraal, construction of a new raw water pumping main from this Pumpstation to the Temba Water Treatment Works, construction of an additional 30 Ml/day module at the Temba W.T.W., the construction of a new 10 Ml reinforced reservoir with baffle walls, upgrading of the existing high-lift clear water Pumpstation on the treatment works site, the construction of a new water pumping main from the Temba site to the existing Sekampaneng Reservoir, and all ancillary works, including electrical, automation and communications systems between the various elements for the Temba Water Supply Scheme.

PCI AFRICA was responsible for the mechanical equipment associated with the new Dissolved Air Flotation (DAF) units, the Rapid Gravity Filters, as well as the Ultra Violet Dosing units.

Dissolved Air Flotation Units
Three off DAF units were constructed each measuring 10 meters long x 8,0 meters wide x 5,45 meters deep. Three off Stainless steel 316 L Saturator vessels (with magnetic level control switches) were provided with two off (duty / standby) Atlas Copco rotary screw air compressors to provide air to these units. The automatic control of these Saturator units is PLC controlled. Due to the design of the scum flushing operation, two electrically operated de-scum outlet valves are opened during this operation for each unit.

De-scum operational frequency and length of de-scum is determined via the PLC SCADA system, which is a fully automatic operation on an adjustable timed basis for both interval and duration.

Rapid Gravity Filters
Five off Filters were constructed each measuring 8,1 meters long x 4,2 meters deep, with each half bed measuring 3,65 meters wide. Each Filter basin consisted of two independent basins separated by a common 0,6 meter wide central washout channel running along the length of the Filters, thus allowing each Filter bed to be washed separately. Each Filter basin was equipped with the PCI type ”DA” underdrain system consisting of thin walled laterals and three part polypropylene nozzles encased in 200 mm thick concrete, complete with a triple layer of media for filtration purposes.

Ultra Violet Dosing
In order to economise on the footprint for the Dosing Building, PCI AFRICA supplied and configured two off medium pressure 500 NB Hanovia PAP 500 stainless steel 316L units in parallel, having end entries and top outlets. Each of the chambers are populated with twelve off 3,5 kW UV medium pressure arc lamps. The dosing plant will deliver a minimum end of lamp life UV dose of 40 mJcm² from both chambers configured in parallel, each treating fifty percent of the total flow. The lamps are powered and controlled by a PHOTON series II control panel, equipped with vacuum fluorescent text displays and membrane keypads for access to the control menus. A low level signal is available on the unit and is monitored on the SCADA system to provide an alarm.