Q&A: Collaboration needed as water treatment plants reach capacity

Wastewater management in South Africa is approaching crisis levels and there is an urgent need for collaboration between different players in the water sector, according to Dr Rembu Magoba, the water manager of the Council for Scientific and Industrial Research (CSIR). 

Wastewater is water that has been used before. It is water from homes and businesses and includes substances such as human waste, food and chemicals.

The Green Drop report recently revealed the poor state of water infrastructure and management in the country. It showed that of the country’s 955 municipal wastewater treatment plants, 334 are in a critical state. 

With our wastewater treatment discharging waste and sewage into our rivers and oceans, people are at risk of getting diseases that may sometimes be fatal. 

“If water is not properly treated we can anticipate the ongoing destruction of our rivers, wetlands, oceans and all organisms and creatures living in these systems,” said Dr Kevin Winter, a senior lecturer in the UCT department of environmental and geographical science. 

“When this happens we lose a significant food source; we become dependent on polluted water to irrigate food and soil on the land; we lose nature-based systems that clean, and purify water. This is a significant loss”. 

Winter said wastewater can be put to good use as it often contains valuable resources such as nitrogen, phosphate and ammonium. “If the nasties, like heavy metals, are separated from the waste, these nutrients can be used as fertilisers to support food security.” 

This, he said, is why he does not believe in the term “wastewater” as that water can be treated to a particular quality and used for a particular purpose.

The M&G asked Winter to go deeper into what wastewater is and how it can be managed. 

What is wastewater?

Traditionally, wastewater is water that enters a wastewater treatment plant and is processed, often poorly, and then discharged as wastewater. 

But I am surprised we are still using this term and idea in a water-scarce country. There should be no such thing as waste water. It seems convenient to talk about “waste” when we can no longer think of a reason to use it in its current condition. So, inevitably what has happened is that because we can’t deal with the treatment of poor water quality and therefore can’t use the water, we label it as waste.

So, we need to turn this around. All water is valuable but the quality of the water poses certain risks. All I am saying here is that the concept of wastewater is odd and completely out of place in a water-scarce country.

How is it managed?

Conventionally wastewater, usually from industrial and domestic homes, is piped to a wastewater treatment plant that attempts to deal with a load of contaminants that arrive at the plant in varying volumes and levels of quality. 

It is a complex process, but in summary: solids are settled out of the water (taken to landfill at some stage once it is dewatered); oxygen is breathed into the remaining water, usually in a slow stirring process; chemicals are added to precipitate compounds, heavy metals, nutrients, et cetera; more chemicals are added to “kill” the bacteria. Finally, the water is discharged to rivers, coastal areas or wetlands. 

What happens if it is not managed properly?

The consequences are all too evident. Hartbeespoort dam is constantly in the news, but so are many others too. Milnerton lagoon has often been given the title of the “big stink”. I will highlight one consequence: polluted water decreases the ability of nature to treat water naturally. Once plants lose their capacity to treat water and pollutants accumulate in lakes and river beds, the ecological system collapses. 

When you get to that stage, there is little hope that water resource quality can be restored. Nearly 70% of South Africa rivers are at a point where there is little possibility of restoring them to [the state they were in] a few decades ago before we damaged water sources. That is serious and we are watching this unfold with very little power to reverse the situation. Our water resources are at stake.

What are some of the ways it can be fixed?

My research team is involved in studies in which we use nature-based processes to treat highly contaminated water that is being discharged into a river. 

We remove almost 90% of the nutrients, and nearly 100% of bacteria and increasingly find that we can trap about 60% of the emerging contaminants in this water. The water is used safely to irrigate edible crops and keep freshwater fish alive. The demonstration plant offers a means of treating the discharge from wastewater treatment plants.
There are more efficient ways to process wastewater in a water scarce country such as South Africa. There is a lack of funding and adequate technologies to deal with wastewater. These need priority.

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