Hard truth about OUR WATER SUPPLY

BY DR ANTHONY TURTON

SOUTH AFRICA has always been a waterconstrained country.

The discovery of gold in 1886 therefore posed a major challenge, which impacted on the way our water and energy systems were engineered over the next century and a half.

The Witwatersrand Goldfields were in the centre of the country, on top of a high-altitude plateau that was so water scarce that only a treeless grassland could exist naturally. The engineering challenges were immense, because water had to be pumped from distant sources to supply the growing Witwatersrand economy. This required large amounts of energy.

In fact, about 10% of the energy budget in a typical Gauteng municipality is for water treatment. But it becomes complicated for two reasons.

First, all our wastewater flows by gravity into large treatment plants. Energy is needed to process the raw sewage, through a cascading process in which oxygen is first added and later removed to create the ideal conditions needed for microbial activity.

At the core is the role played by microbes in digesting waste, and processing nitrogen as it changes form from ammonia to nitrate.If the process is disrupted because of an energy problem, then the bacteria are unable to do their work in making sewage safe.

Second, all our processed sewage is discharged directly into the same rivers from which our drinking water is sourced. This is known as an indirect reuse model, which has worked well for more than a century, but is no longer functional for a variety of reasons.

Collectively, we discharge around five billion litres of sewage daily into our rivers, only about 15% of which is treated to a standard that is safe for recycling back into our drinking water. This is why the sludge dewatering fails. This is what happened at Rooiwal WWTW where the cholera crisis occurred.

Green Drop Reporting Standard is so important, because it is the guarantee that the effluent going back into our rivers is not harmful to people when reused.

The Eskom crisis has triggered a domino effect that is cascading across our entire economy.

The first domino to fall is the initial pumping of sewage into wastewater treatment works (WWTW). It is a common sight across every town and city to see raw sewage flowing from a manhole, into the nearest river.

This contaminates the raw water from which our drinking water is later produced. The cholera crisis is a current example of this.

When the four dominos fall, the WWTW is overwhelmed, so untreated effluent is discharged into the river, because the system has no storage capacity.

What flows in has to flow out, so disruptions to the electricity supply mean that untreated sewage has to be discharged into the river.

The sewage contaminated water now flows down the river into the first abstraction plant where potable water is produced.

Here, the fifth domino kicks in, because electricity is needed to drive the water through the reservoirs and water towers full. Without energy, reservoirs run dry, and consumers are left stranded, factories are unable to operate, and hospitals and schools become hazardous places where disease can spread rapidly.

This simplified explanation shows that at least six dominoes inevitably fall in succession, once the first one drops. This is how the energy crisis propagates through the economy, like ripples on a pond, radiating outwards in ever-expanding circles of disruption.

What can the individual person do? There is no easy answer, other than to accept that this is our new reality, and then adapt behaviour accordingly.

The second domino to fall is the injection of oxygen into the sewage on arrival at the WWTW. This is typically done with a bank of turbulators that vigorously stir up the waste, flinging it into the air in square ponds with baffles designed to direct the flow. This energises the bacteria needed to start digesting the organic matter. Without electricity, the turbulators fail, and so the bacteria are starved of oxygen, and they die.

The third domino to fall is the pumping system that separates the solid and liquid material in settling tanks known as clarifiers. The sludge settles to the bottom, where the fourth domino falls when the various stages of treatment to make it safe for human consumption.

None of our water treatment plants – even the biggest like Rand and Umgeni Water – were designed to render sewage contaminated river water safe for human use.

Once the potable water has been treated, it is pumped over vast distances in high-pressure pipes to the municipalities. This is where the sixth domino kicks in, because the pumps are massive, consuming vast amounts of energy.

On delivery to the municipality, the seventh domino becomes relevant, because smaller pumps keep

Adaptive behaviour embraces a new culture of reuse, recovery and recycling where appropriate. It also requires alternative storage close to the point of use.

There are many point of use solutions being developed, so make use of a reputable service provider to advise on the best choice for your own needs.

This is our New Normal, and it will alter the way we live our lives in future. But it is survivable, so take heart and learn about the options available in the solution space.

Dr Anthony Turton is a specialist in water as a national security risk and holds a professorship at the University of the Free State