By Nneka Nwogwugwu
South Africa, which witnessed a year-long drought in Cape Town, is using new, unique methods to increase its water supply: By recycling and reusing its wastewater.
The country is using phycoremediation or the ‘use of algae to treat wastes or wastewaters’ towards this end in a number of its provinces.
One such instance is the Zaalklapspruit wetland system, some 75 kilometres from the Loskop Dam on the Olifants river in Mpumalanga province.
Authorities were spurred into action after a large number of crocodiles, terrapins and fish died in the mid-2000s in the dam.
The reason for the die-off was acid mine drainage, untreated sewage and industrial and agricultural pollution, which severely impacted the water quality. Mpumalanga is home to many of South Africa’s coal mines.
Paul Oberholster, formerly of South Africa’s Council for Scientific and Industrial Research (CSIR), and currently director of the Centre for Environmental Management at the University of the Free State, said:
“It doesn’t help trying to close down coalmines, because of the jobs they provide and their role in energy generation in South Africa. I therefore rather choose to work with mines and in doing so, try and change their management principles.”
Oberholster said the major sources of acid mine drainage spills in the area were not necessarily those mines currently in operation, but rather the abandoned ones that were mined from the 1930s. There are at least 3,000 abandoned mines in Mpumalanga.
Tests show that the algae filter out around 74 per cent of phosphates, a nutrient that can cause harmful toxic blue-green algae bloom.
The algal species were first isolated at the CSIR, where Oberholster previously worked and has since been cultured in five 5,000 litre translucent water tanks on site.
They are released into the system when ready. They rid domestic wastewater of nutrients such as phosphates and nitrogen and create conditions under which E.coli levels are reduced.
The low-cost passive system does not use chemicals nor electricity — crucial in a country such as South Africa suffering from electricity supply issues.
Oberholster believes one could raise fish in such a system, or produce an alternative biomass source (in the form of dried-out algal-rich sludge) for bio-energy production — an attractive option given the depletion of fossil fuels and the need to manage climate-changing greenhouse gases.
This aspect was piloted in a similar phycoremedial project at Brandwag, a 500-strong farming community in the Southern Cape.
There, algae cultivated in three tanks have been added since 2016 to an existing pond micro-water treatment system that handles the wastewater Brandwag residents produce daily.