by Acesulfame is a sweetener found in sugar-free drinks and foods. Since it cannot be metabolized in the human body, the sweetener ends up in the waste water after consumption and remains largely intact in sewage treatment plants. A new study from the University of Vienna shows that the persistence of the sweetener varies with temperature, as the concentration of the sweetener in wastewater varies with the seasons. The environmental geosciences team analyzed how groundwater flows can be tracked using these seasonal variations. Since residues of the sweetener get into the drinking water, acesulfame serves as an indicator for the origin and composition of our drinking water. The study has now been published in the journal water research.
The sugar substitute acesulfame is one of the most commonly used sweeteners in Europe. It’s nearly 200 times sweeter than sugar and temperature stable, making it suitable for sugar-free baking and sweetening most diet sodas. Since the substance is not metabolized by the human body, large quantities of it enter the sewage system when consumed and remain there after treatment, albeit in fluctuating concentrations. The new study by the University of Vienna shows that the substance is degraded to varying degrees over the course of the year, depending on the temperature. “For a long time it was assumed that the potassium salt of acesulfame was not broken down at all in sewage treatment plants. That still applies today, but only during the cold season,” explains Thilo Hofmann, deputy head of the Center for Microbiology and Environmental Systems Science at the University of Vienna. “There were already initial indications that at least partial biological degradation takes place in summer. We can prove this in our study and show systematically over a longer period of time how the concentration of the sweetener in the water changes with the seasons.”
Sweetener acesulfame: indicator for the flow paths of waste water treated in sewage treatment plants
Acesulfame is a widespread indicator of wastewater discharges into surface water and groundwater: since this sweetener is not completely degraded both in sewage treatment plants and in the environment – after it has been discharged into water with the treated wastewater – it is possible to detect the substance in the water indicates how much treated wastewater has reached groundwater, rivers or lakes. “Anyone who follows the traces of the substance can ultimately understand the flow paths of the wastewater and its mixing with the groundwater,” explains Hofmann. With the knowledge of seasonal fluctuations in the breakdown of the substance, acesulfame becomes an even more meaningful tracer.
Computer models of groundwater flows enable risk prevention
“Our study shows that the seasonally fluctuating concentration of acesulfame can be used to better visualize and understand underground processes, i.e. groundwater flows,” says Hofmann. Wastewater components in drinking water can be recorded, as well as the flow rate of groundwater and the mixing ratio of groundwater and river water. The environmental geoscientists evaluated river and groundwater samples that were collected regularly over a period of eight years in a foothills of the Alps. The research team linked their analyzes with computer models that calculate underground water flows. “Such computer models are the key to risk prevention, because they can be used to understand how much river water and how much groundwater gets into the drinking water of the population and how the operation of waterworks can be optimized,” adds the head of the research group.
Traces of the sweetener get into the drinking water
The sweetener acesulfame thus leaves a trace of waste water, river and ground water to our drinking water. “The fact that acesulfame is not broken down is fundamentally good for us hydrogeologists, because we can draw valuable insights from it,” says Hofmann. He adds: “But this circumstance also makes us aware that our lifestyle is reflected in the waste water and thus also in the drinking water: The sugar substitute we consume ends up back in our drinking water – albeit heavily diluted, of course.”
