Gauteng and NW Province

How to solve cities’ great problem of water supply

The article below appeared on 31 March 2014 in Business Day.

31 March 2014, Johannesburg. While potholes and road washaways are considerable problems, our biggest water challenge in SA is water scarcity and increasing the efficiency of water use, writes Francis Gibbons

IT’S EASY to paint a picture of extremes when it comes to water. The above-average rainfall over the northeastern half of South Africa over the first two weeks of March, in some places more than double the average for the period, with associated flooding and tragic loss of life, should be considered against severe droughts elsewhere in the world, for example California and Queensland. While potholes and road washaways are considerable problems, our biggest water challenge in South Africa is water scarcity and increasing the efficiency of water use.

The focus of the United Nations’ (UN’s) World Water Day this year is on the water-energy nexus. Water and energy are fundamental to our urban existence and are interdependent. Ninety percent of power generation is water-intensive, and the amount of energy used in pumping and treating water and wastewater amounts to 8% of the global energy generation. So saving water saves power, which saves water, and so on.

World Water Day also has an objective of raising awareness of the continuing inequity in access to safe drinking water, adequate sanitation, sufficient food and energy, especially for the “bottom billion”, people who live in informal settlements and impoverished rural areas.

While the world population is expected to grow by 2.3-billion from the current 7-billion to 9.3-billion in 2050, urban population is expected to grow by 2.6-billion (from 3.6-billion to 6.2-billion). Most of this urbanisation will occur in the developing world, already struggling with the provision of water and electricity to its urban populations. Africa is projected to see its urban population increase by 900-million.

In the National Development Plan’s forecast for South Africa in 2030, the population is expected to grow from the 2011 census figure of 51.7-million, with 62% living in urban areas, to about 60-million, with 70% in urban areas. Gauteng’s mainly urban population is expected to grow from 11-million to 14-million. The main challenge in meeting increased water demand in water-scarce areas is that additional fresh water resources are increasingly remote from the demand centres — resulting in increasing power consumption per unit of water transported. As South Africa’s ground water reserves are limited, desalination of seawater using reverse osmosis will undoubtedly be adopted in future by many cities near the coast. But desalination uses three to four times the amount of energy used in conventional fresh water treatment. Improving the efficiency of current water use has to be the goal before additional desalination capacity is considered.

Considering the wastewater part of the urban water cycle, the UN reports that more than 80% of the water used worldwide is neither collected nor treated. This threatens human and environmental health and leads to huge inefficiencies in the water cycle. The picture in South Africa is much better: our problems stem more from the lack of operational capability and maintenance. The embargo on the release of the 2013 Green Drop report leaves us ignorant as to the latest statistics in this regard.

Collecting and treating wastewater is an environmental and social imperative. But if the inefficiencies in the urban wastewater cycle are examined, in addition to water loss management, what we should be doing more is recycling our wastewater. This will provide the next source of economical water — after economically viable freshwater sources are fully used — to limit the reliance on more costly (and energy-intensive) seawater desalination.

Is a paradigm shift possible in the way we use water in urban areas? What if instead of trying to supply 100% of the domestic water demand to a house, complex or block of flats, and collecting the wastewater (usually 80% of the amount supplied), we supplied only the 20% that makes up the difference! So each house, complex or block would have its own water recycling plant. None of us is keen to drink our own purified household wastewater, even with the advanced treatment technologies and safety barriers. But will that be the case for the next generation? Or the one after?


 By recycling grey water for irrigation and harvesting rainwater for either irrigation or household use we save water and work towards a greener future.

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