South Africa is a water-scarce country so it is imperative to look after our water resources, including wastewater. The water that we use to shower, bath, wash dishes and flush toilets still has value if it processed with the right techniques.
Most of our wastewater is sent to treatment plants to be cleaned and sterilised before being discharged back into the environment. However, much of our used water is simply drained into the ground or into underground aquifers and diverted to the ocean.
If South Africa can recover this wastewater and turn it into a resource, we can unlock its inherent value and curb the effects of severe droughts and empty dams. The process is not easy and used water can contain a number of chemicals and contaminants. Scientists are exploring more efficient and cost-effective ways of turning this dirty water into valuable, potable water.
Wastewater can be a source of energy
South Africans need to start viewing wastewater as an asset. Water treatment plants can become resource recovery facilities that recoup energy from the water. Through a process of anaerobic digestion, microorganisms can ‘feed’ on the organic materials contained in the water, producing biogas in the process.
This biogas comprises about 50% methane which is a valuable and renewable fuel for boilers and furnaces. The biogas can also be an alternative to coal in the production of electricity, cement and other industrial products.
Wastewater can also be treated in a hydrothermal process whereby sewerage sludge (the solids that are removed from the dirty water during treatment) is converted into biofuel. This type of organic fuel is a renewable alternative to petrol and diesel. These sorts of systems can turn our used water into a source of energy.
Wastewater contains valuable nutrients
Nutrients such as nitrogen and phosphorous are abundant in used water. These elements are essential for plant growth. The nitrogen is harvested from ammonia in the dirty water and is used to create fertiliser.
Sanitised wastewater also contains potassium and magnesium. These nutrients have a range of applications in industrial processes and manufacturing. If water treatment facilities are equipped to recover these nutrients, South Africa will be able to harness the value contained in effluent.
Researchers are already examining ways of turning used water into fertiliser. So far, they have created crop yields of similar proportion to those that use commercial fertilisers. As the science matures, wastewater could become a major source of value for the agricultural sector.
Precious metals can be found in used water
Wastewater contains a variety of metals – some of which are toxic to marine life and others that are extremely valuable. However, conventional removal techniques currently require a lot of energy and they can create toxic byproducts.
Scientists are looking at new ways of removing precious metals and toxic elements from this water. Membrane systems are being developed to selectively remove precious metals from the water. Other technologies include using microorganisms and biosystems to recover the metals.
Used water is a valuable resource that needs to be unlocked. Its benefits far outweigh the ease of treating it and sending on its way to the ocean. It can be used as a source of energy in the form of biogas and methane, as well as to improve the fertility of crops in the agricultural industry. South Africa needs to unlock this waste source and its potential.
Averda is a leading waste management provider with over 50 years of experience across three continents. Through growth, transformation and engagement, we strive to find new ways of managing waste while protecting the community and environment.
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