Rand Water has assured consumers on its social media sites that it uses a disinfection water treatment process to destroy bacteria such as the one that causes typhoid fever.
At Rand Water, we have a global reputation for providing water of high quality that ranks among the best in the world. We have consistently met and exceeded national standards and international guidelines on water quality. #RandWater #WaterWise #KnowBetterDoBetter
[NS] pic.twitter.com/efZkCN6e13— Rand Water (@Rand_Water) March 7, 2022
“We have consistently met and exceeded national standards and international guidelines on water quality,” it said.
The water utility supplies potable water to 11 million people in Gauteng and parts of Mpumalanga, North West and Free State.
It said it purified about 3 600 megalitres of water per day and distributed clean drinking water, “free of harmful micro-organisms and chemical contaminants” to 58 reservoirs, via 3 000km of pipelines, to 19 water services authorities.
“The quality of this drinking water is regularly monitored during the purification process and distribution system.
“It complies with requirements by the South African National Standard for Drinking Water (SANS 241) and the World Health Organisation.”
“It is safe to drink straight from the tap.”
ALSO READ: No typhoid fever-linked bacteria found in water – Rand Water
1/2 The white or cloudy color in your tap water is simply due to fine air bubbles. High pressure in the distribution pipes causes trapped air to dissolve in the water, as soon as the pressure is released by opening the tap, the bubbles reform, giving the water a white appearance pic.twitter.com/0MIARZHDDU
— Rand Water (@Rand_Water) March 7, 2022
Here is the purification process:
Rand Waters draws raw water from the Vaal Dam via a canal and a gravity pipeline and by pumping from the Vaal River Barrage Reservoir at the Lethabo weir.
The conventional treatment process removed suspended materials and disinfected the water before pumping it to the provinces as well as the mining industry and other large industrial concerns.
“The purification process, at each stage, is accompanied by changes in the physical and chemical composition of the water. These changes are constantly monitored. Corrective action is taken to ensure that the quality conforms to prescribed limits.”
Once the material is removed, a screening process would take place at the purification station where water is channelled through metal screens to trap organisms such as sticks, leaves and litter.
Rand Water said the next process was the removal of particles from all raw water.
“The water from the Vaal Dam contains highly dispersed particles which, because they are colloidal, tend to remain suspended for a very long period.
“Settling of these suspended particles is aided by adding chemical coagulants such as calcium hydroxide.”
It said the calcium hydroxide was produced when raw limestone was heated in a kiln to convert it to calcium oxide and carbon dioxide gas.
“The burnt limestone is then crushed and water is added, in slakers, to destabilise the electrostatic charges of suspended particles in the water.”
A small quantity of activated sodium silica was also added to the raw water to promote flocculation if required.
Sludge was also separated from water through disposal.
“Between 500 and 800 tons of dry sludge is produced each day during the purification process. This is removed from the sedimentation tanks as a thin slurry containing 3% mass by the volume of dry sludge.”
We are proud of our internationally acknowledged reputation for supplying water of acceptable quality, meeting the national drinking water standards
(SANS 241).
Our customer base includes municipalities, mines and industries.@DWS_RSA #RandWater #WaterWise #KnowBetterDoBetter pic.twitter.com/FioKymGjwD— Rand Water (@Rand_Water) February 23, 2022
The sludge is pumped to Rand Water’s sludge disposal site at Panfontein.
“Here it is dosed with an organic flocculent in gravity thickening plants to aid the separation of the solids from the liquid. The clear supernatant fluid is drawn off and returned to the purification system. The thickened sludge is pumped onto drying beds where it is dried by evaporation.”
The next step is carbonation – the use of lime as a coagulant raises the pH of the water to about 10,5 which is very unstable and conducive to scale forming.
“After sedimentation, the water flows into carbonation bays where it is stabilised by adding pure carbon dioxide gas to the water. This lowers the pH to between 8,0 and 8.4.”
Following carbonation, the water passes into the filter houses where it flows through rapid gravity sand filter beds of finely graded silica sand and pebbles.
“The remaining suspended particles are removed at this stage, where ferric chloride may be added before filtration to enhance the process.”
The last step was chlorination, where water leaving the purification plant was disinfected with chlorine to kill micro-organisms, bacteria and viruses that may be present in the water.
“The free available chlorine concentration must be between 0,8 and 2,5 mg/l depending on the raw water quality to ensure that all pathogens are killed.”
Water supply would take place, where clean water was pumped through underground pipes to booster pumping stations.
“Although free available chlorine is an excellent disinfectant, it does not remain active for much longer than six to eight hours.
“At the booster pumping stations, monochloramine is produced in situ by dosing chlorine and ammonia at a mass ratio of not less than 4:1. This is a less powerful disinfectant but can prevent microbial growth in the water for up to eight hours to 12 days.”
From the booster pumping stations, the water is pumped into reservoirs, where Rand Water then sells it to various local authorities that supply homes, schools, businesses and factories with clean water.
Top ways to #SaveWater.
Let's all reduce our water consumption. @Senzo_Mchunu_ pic.twitter.com/6u3XkZH7mQ
— Water&SanitationRSA (@DWS_RSA) March 1, 2022
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