Water purification process decoded
Zuikerbosch Pumping Station in Vereeniging is a water treatment plant that produces no less than 3 600 megalitres of clean water every day.
Zuikerbosch Pumping Station in Vereeniging is a water treatment plant that produces no less than 3 600 megalitres of clean water every day.
With water streaming consistently from the Vaal Dam, and other sources, the station operates 24 hours a day.
Yvonne Rakobane, Zuikerbosch process quality manager, says the premises have to be kept neat and clean at all times.
“We are Blue Drop compliant, which means the quality of our water is of a universal standard.”
There are eight main processes in water purification.
In the screening process, raw water goes into the purification station through metal screens.
These screens act as a sieve, keeping all unwanted particles out of the water while allowing the water to pass through.
The particles include fish, litter, plants and others.
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“Ninety-five – 97 per cent of the particles, called floc, are extracted during the screening.”
The water then moves to the next stage, where it is coagulated.
“In coagulation, we add a chemical such as alum which produces positive charges to neutralise the negative charges on the particles.
“Then the particles can stick together, forming larger particles which are more easily removed,” explains Sekwala Mangwale, the senior process quality technician at the plant.
The particles then sink to the bottom of the tank.
“In sedimentation, the new floc at the bottom of the tank is now referred to as sludge and is pumped out by desludging bridges.
“At this point, the water at the top of the tank is cleaner than when it came in.”
The sludge is then pumped into Rand Water’s sludge disposal site at Panfontein.
“During sedimentation, the use of lime as a coagulant raises the pH of the water to about 10.5, which is conductive and scale forming.
“Here, the water is stabilised by adding carbon dioxide to control the pH,” adds Mangwale.
To prevent algae inside the filter house, the light intensity is kept at 15lux (15 lumens per square metre).
The water is then pumped through layers of sand.
This is done to further trap any particles left in the water.
Rakobane explains: “The different grains of sand are backwashed to remove the particles after the clean water passes.
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“In the disinfection process, chlorine is added to the water, to remove harmful bacteria.”
Rakobane says quality monitoring and assurance on site is one of their most important priorities.
“After all the processes, we have to make sure the water is as good as it should be.”
The plant is equipped with a fully automated lab that keeps track of the water quality every minute.
This allows officials from the plant and other locations to log in and check the sample readings whenever they need to.
