The degradation of river systems in South Africa has been linked primarily to the inability of municipalities to properly treat wastewater. According to the 2022 Green Drop Report, out of the existing 850 wastewater systems across 90 municipalities, only 23 (or less than 3%) qualified for the Green Drop Certification. This underscores the depth and breadth of the wastewater treatment crisis in South Africa and its potential implications for human and environmental health.

In 2030, billions of people will still lack access to safe water, sanitation and hygiene services – the most basic human need for health and well-being. Target 6.1 of the United Nations (UN) Sustainable Development Goals (SDGs) – SDG 6 – aims to achieve universal and equitable access to safe and affordable drinking water for all, while target 6.3 is also looking to improve water quality by reducing pollution, eliminating dumping and minimising release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe re-use globally by 2030.

These challenges inform Prof Voua Otomo's research, which focuses on the drivers of river pollution in the Qwaqwa region, ways to mitigate/remediate their effects, and the development of simple and quick methods to assess water quality. His research, which is part of the UFS 2023 Impact Report, has drawn attention to localised incidences of terrestrial and aquatic contamination linked to sewage sludge management by local wastewater treatment plants.

Using mycofiltration to reclaim the quality of contaminated water

In Qwaqwa, wastewater treatment plants, however, are not the only source of river pollution, as a significant amount of river pollutants emanates directly from the communities that often dispose of their household waste directly into the waterways. This has led to unacceptable levels of pharmaceuticals such as biphenyl-4-ylacetic acid (an anti-inflammatory), efavirenz (an HIV medicine), and carbamazepine (an epilepsy medicine) ending up in rivers.

To attempt to reclaim the quality of contaminated water, ongoing research in Prof Voua Otomo's laboratory involves the use of 'mycofiltration', i.e., the use of fungal mycelia for the purpose of water filtration. This relatively untapped eco-friendly technology is attracting more attention, yet its real merits are only now being established and documented scientifically.

"Various species of fungi have been explored in bioremediation studies, and those belonging to the Pleurotus genus (edible mushrooms) have demonstrated an exceptional ability in the biosorption of contaminants," says Prof Voua Otomo.

In his field of research, Prof Voua Otomo says snails can be used as bioindicators (i.e., organisms used to assess the health of an environment or ecosystem, particularly by indicating the presence and impact of pollutants or other environmental stressors) or biomonitors (i.e., organisms or a biological systems used to assess the health of an environment, particularly by detecting changes in the levels of pollutants or other harmful substances).

"We designed a mycofilter made of mycelia from the mushroom species Pleurotus ostreatus and filtrated water contaminated with the organic insecticide imidacloprid and the inorganic chemical iron (III). The results showed that mycofiltration could remove up to 94% of iron (III) and 31% of imidacloprid.

"Mycofiltration works through a process called adsorption, which is the process where molecules, ions, or particles from a gas, liquid, or dissolved solid, stick to a surface. This happens when the adsorbate (the substance being adsorbed) attaches to the adsorbent (the surface it adheres to)," Prof Voua Otomo explains.

Mycofiltration viable and affordable for water remediation

This research is the brainchild of Sanele Mnkandla, a final-year PhD student in Prof Voua Otomo's laboratory. "A few years ago, she suggested looking at mycofiltration as a means to improve the quality of contaminated water. Freshwater snails were the most suitable organisms to help assess the improvement of the water quality after mycofiltration," explains Prof Voua Otomo.

According to him, they are currently exploring ways to upscale the mycofilter to improve the quality of larger bodies of water, including rivers. The duration of the process depends on the size of the filter, the amount of water to be filtered and the targeted chemicals. Bigger filters, explains Prof Voua Otomo, will filter larger amounts of water over a relatively longer time whereas smaller ones will be saturated quickly. The process could last from minutes to days.

"We have published a technical note on the topic and a proof of concept. We are currently testing this technology using wastewater effluent in the Qwaqwa region. We are also exploring local applications in rainwater harvesting.

"Mycofiltration is certainly a viable and affordable option for water remediation, which can find a wide range of applications in South Africa," he says.

Photo captions:

Prof Patricks Voua Otomo, Associate Professor and subject head of Department of Zoology and Entomology at the University of the Free State (UFS).

Mycofiltration of ferric iron aqueous solution.

Pleurotus ostreatus mycofilter. Thatching straw fully colonised by P. ostreatus mycelia (white).