Traces of drugs are in water worldwide. While the impact of such pollution on the environment and human health is still largely unknown, researchers of the Louvain4Water at UCLouvain are working on a new way to eliminate it from our wastewater
We all take medicine. Some products, such as paracetamol or ibuprofen,1 are rapidly metabolised by the body and eliminated via urine and stool. Almost all of our waste water goes through waste water treatment plants. However, traces of drugs are found, in various concentrations, in almost all surface waters (streams, ponds, seas, etc.), in Wallonia as elsewhere. However, it’s technically possible to further purify the waters we release into nature.
Three treatment phases
Sewage treatment methods differ from one country to another. In Belgium, waste water treatment is normally done in two stages:
- Primary treatment filters the water so as to eliminate fats, large particles and waste (sand, insects, plants, etc.).
- Secondary biological treatment involves pouring waste water into large basins where activated sludge made of microorganisms degrades organic substances.
Many substances resist these basic treatments. Depending on the use that will be made of water, tertiary treatment may be necessary: sand filtering, ozonation, addition of chlorine, etc. But that's not always enough, especially when the water is loaded with persistent micropollutants.
Clean up with free radicals
‘Some drugs aren’t biodegradable and resist conventional treatments’, says Raphaël Janssens, a civil engineer at UCLouvain. ‘Such waters must then be subjected to advanced oxidation treatment. It’s a question of producing free radicals [OH°] that will degrade the polluting molecules. Indeed, through their high oxidising power, free radicals attack any organic matter present in water: drugs, but also hormones, pesticides, nicotine, caffeine, etc.’ All of these substances are suspected of having a deleterious impact on the environment, aquatic ecosystems and even human health.
How to produce free radicals?
There are several techniques for producing free radicals. As part of tertiary water treatment, ozonation and activation of hydrogen peroxide by ultraviolet (UV) rays are already used. But these techniques have a disadvantage: they’re energy-consuming in terms of consumables. Mr Janssens and Patricia Luis Alconero, a professor at UCLouvain’s iMMC, and member of the Louvain4Water, working on a new free radical production technique: photocatalysis. ‘Our photocatalysis technique consists of using metal particles called photocatalysts which are activated by UV’, they explain. ‘There are two ways to do photocatalysis. Either by immobilising the catalyst particles on a surface, or by using them in suspension. This second technique requires an additional filtration step to recover the photocatalysts. But it can handle a larger volume of water because a larger catalyst area is exposed to UV rays.’2
The challenge of anticancer drugs
It’s all about volume. ‘In Belgium, each person uses an average of 110 litres of water a day’, Mr Janssens says. ‘The quantities of waste water to be treated are therefore gigantic. We must find a way to proceed that is effective, economically and ecologically efficient, and sanitary.’
As part of his thesis, Mr Janssens is interested in anticancer drugs that abound in waste water from hospitals and elsewhere. With the increase in outpatient treatment – not requiring hospitalisation – more and more cytotoxic agents are being flushed out of patients' homes. ‘But these drugs have been designed to prevent the reproduction of cancer cells in a persistent way’, he says. ‘In the long run, it's not impossible that they can mutate the DNA of aquatic organisms.’
One solution would be to treat patient urine even before it ends up in waste water. But photocatalysis doesn’t work very well on urine. ‘We don’t yet have a magic bullet to propose, but we’re studying closely the techniques that could limit or even prevent this drug pollution’, Prof. Luis Alconero concludes. It’s a form of pollution that, given the population’s aging and the increase of chronic diseases such as cancer, will only increase in the coming years.
(1) Paracetamol and ibuprofen are over-the-counter painkillers and fever reducers. (2) R. Janssens et al., ‘Slurry photocatalytic membrane reactor technology for removal of pharmaceutical compounds from wastewater: Towards cytostatic drug elimination’, Science of the Total Environment, 2017.
A glance at Patricia Luis Alconero's bio
Patricia Luis Alconero is a researcher and professor at UCLouvain's Institute of Mechanics, Materials and Civil Engineering (iMMC). She earned her chemical engineering degree in 2004 from the University of Cantabria (Spain), where she also earned her PhD, in 2009. Following a three-year postdoc at KULeuven, she has been a professor at UCLouvain since 2013. Her research focuses on membrane technologies and the role they can play in cleaning up pollution..
A glance at Raphaël Janssens's bio
Raphaël Janssens earned a master's degree in chemical engineering and materials in 2015 at UCLouvain. Since then, he has been preparing a PhD thesis on the disposal of oncology drugs in waste water from hospitals.