The idea of technology too small to see but having a profound impact sounds like science fiction, but today nanotechnology is not only available, it is increasingly viable for monitoring water quality and treating wastewater.

Nanotechnology is the science and engineering of manipulating matter at an atomic or molecular level at scales of between 1 and 100 nanometres, which is 100 000 times smaller than the width of a human hair. Professor Philiswa Nosizo Nomngongo, the South African Research Chair (SARChI) in nanotechnology from the University of Johannesburg, explains that this manipulation enhances properties like strength and conductivity, which then allows for specialised applications.

Prof Nomngongo has been a part of the water sector for a long time. Her interest in water stems from experiencing water issues as a child while her focus on nanotechnology developed during her academic journey. She explains, “When I was doing my research for master’s degree I needed a way to detect pollutants. My supervisor told me that we needed to make sensors for that.”

The concept of nanotechnology traces its theoretical conception to the 1950s, but Prof Nomngongo explains that it wasn’t until 1981 that the science caught up for practical use. The use of nanotechnology has been embraced by many fields and has many important uses in the water sector.

Water monitoring on the nanoscale

Prof Nomngongo says, “Nanotechnology can greatly improve water monitoring. If you are concerned about metals in water, you can develop nanosensors that not only detect metals but also give you concentration data. If you are concerned about chemicals in water, there are nanosensors for that, too. An easy-to-use, immediately helpful nanosensor that changes colour when exposed to certain pollutants can help identify problems faster.”

This approach is preventative and cost-effective, as it reduces the amount of testing needed to identify problems. Prof Nomngongo also explains that, in some cases, nanotechnology can be used in solid-phase extraction, where nanomaterials can trap the pollutants to help further analyse them. “This is especially helpful when the pollutants are found in low concentrations. These materials can be made to only interact with specific pollutants, chemicals or metals. If you are concerned about pharmaceuticals, then the material can be designed to trap certain chemicals and avoid others.”

Treating water with nanotech

Not a one-trick pony, nanotechnology is also used to treat water, Prof Nomngongo says, “When treating raw water or wastewater, it’s the same principles at work.”

Membrane repair is a prominent example, where the membranes of water molecules are repaired or strengthened to aid in reverse osmosis. Borrowing from the same technology used to trap pollutants for testing, water can be passed through a column packed with nanomaterials, and as it passes through, the pollutants become trapped, and clean water flows out. Prof Nomngongo also explains, “We can also use catalysis to break down certain molecules into less toxic ones. Combining adsorption and catalysis, where some nanomaterial traps pollutants and others break down toxic compounds into safer varieties.”

Current projects

Prof Nomngongo’s current research involves monitoring the presence of pharmaceuticals in water, specifically antibiotics.

“To treat water effectively, we need to understand what is happening within it. I am focused on monitoring pollutants in water with nanotechnology so that the treatment is correct and specific and not broad.”

This means that dangerous compounds in the water can be treated with context-specific nanomaterials to correctly absorb or break down these toxic compounds.

Another project Prof Nomngongo is working on is the use of nanomaterials to trap E. coli. This is motivated by her research, which indicates an abundance of E. coli found in rural parts of South Africa, and complex treatment is often not possible. Nanotechnology offers hope in treating this water through a filter process.

For the professor, the promise of nanotechnology lies in its ability to push beyond current treatment processes and tackle complex problems like antibiotics or E. coli in water. She says, “Currently, we are treating for some pollutants and not others, but with nanotechnology, we can create advanced treatment processes that offer safer water.” This is especially important in the South African context, where Prof Nomngongo sees decentralised solutions as a practical way to overcome water issues in rural South Africa.

She does add that “the cost is still a prohibitive barrier. Producing effective nanomaterials can be expensive and difficult to scale.” Despite this, she remains optimistic about future uses, saying, “The development of simpler, more accessible tools that are easy to use, similar to litmus paper, would be transformative and enable non-specialists to monitor water.” This would empower people across South Africa, especially in rural areas where water monitoring and treatment are still difficult.