Comprehensive study on the removal of pharmaceuticals
Big step in research into pharmaceuticals in water
Research tells us that groundwater and surface water contain pharmaceuticals and their transformation products. Pharmaceutical residues and transformation products are expelled by the body and, via wastewater, end up in surface water and groundwater. Over the past few years, KWR has worked on acquiring more insight into the substances that reach drinking water sources through this route: What is their molecular structure? What is their impact on aquatic life, and on humans and animals? And how do you remove them from the water when producing drinking water? Or how, when treating wastewater, do you keep them from getting into the surface water?
It is striking that the literature and research have tended to select a very limited number of pharmaceuticals and related substances as targets for removal, and have often studied their removal through the application of only a single treatment technique. “We decided to take a better approach,” says Roberta Hofman-Caris. “Together with a number of different parties – water companies, waterboards, players in the pharmaceutical and medical world – and drawing on all disciplines concerned, we took up the challenge. In a large-scale study, we made a much wider selection of the most relevant compounds. We also tested several techniques aimed at rendering the substances harmless: removal with membranes, transformation with advanced oxidation, or adhesion with specific adsorbents.” The study offers the possibility of comparing the techniques with each other and, to a degree, making predictions – through statistics and models – on the removal rates for a broad range of substances. The study is unique, systematic, comprehensive and multi-disciplinary.
Hofman explains the study’s concrete outcome. “We now have an overview of what pharmaceuticals are present in surface water and groundwater, and where. We also discovered that the pharmaceutical load in a river for the most part coincides with what is sold in the river basin area. But the overview is not complete, because we’re not yet able to analyse all pharmaceuticals.” Although the concentrations of substances found are lower, by a factor of one thousand, than levels at which an effect on humans can be expected, all the parties agree that the subject is one that needs to be well researched and effectively tackled.
Researchers are also learning more and more about how to render the substances harmless. “The action of many pharmaceuticals,” says Hofman, “is based on the presence of groups in the molecule that have a particular function. Nanofiltration and treatment with ultraviolet light and hydrogen peroxide help in the removal or transformation of most pharmaceuticals. Whether this works depends on the molecular structure of the pharmaceutical. We now have a better understanding of when it will work and when not.” Substances that are difficult to remove with existing techniques can possibly be tackled with new ones, such as affinity adsorption: with an adsorbent that can effectively adhere to particular functional groups in the molecule, one can remove them from the water. “It’s as if they embraced each other, “ explains Hofman. “That’s why it’s called affinity adsorption.”
© 2017 KWR Watercycle Research Institute