Acesulfame is a sugar substitute found in sugar-free beverages and meals. Because it cannot be metabolised in the human body, the sweetener is excreted in wastewater and remains essentially intact even in sewage treatment plants.
According to a new study from the University of Vienna, the sweetener's persistence varies with temperature, much as the concentration of the sweetener in wastewater varies with the seasons. The environmental geosciences team investigated how seasonal oscillations in groundwater flow might be used to trace groundwater flows. Because sugar residues end up in drinking water, acesulfame can be used to determine the source and composition of our water. The research was just published in the journal Water Research.
The sugar substitute acesulfame is one of the most commonly used sweeteners in Europe. It is almost 200 times sweeter than sugar and temperature-stable, making it suitable for sugar-free baking and for sweetening most diet lemonades. Because the human body does not metabolise the substance, it ends up in wastewater when consumed in large quantities and remains there even after treatment, but in fluctuating concentrations. The new study by the University of Vienna shows that the substance is broken down to varying degrees over the year depending on the temperature.
"For a long time, it was assumed that the potassium salt of acesulfame is not degraded at all in wastewater treatment plants. This is still true, but only in the cold season," said Thilo Hofmann, deputy head of the Centre for Microbiology and Environmental Systems Science at the University of Vienna, adding, "There were already initial indications that at least partial biodegradation takes place in summer. We can prove this in our study and systematically show for a longer period of time how the concentration of the sweetener in the water changes with the seasons."
Acesulfame is a widely used indicator of wastewater discharges into surface waters and groundwater: since this sweetener is not completely degraded both in wastewater treatment plants and in the environment -- after it has been discharged into water bodies with the treated wastewater -- detection of the substance in water indicates that and how much-treated wastewater has entered groundwater, rivers or lakes. "If you follow the traces of the substance, you can ultimately trace flow paths of the wastewater and its mixing with groundwater," Hofmann said. With the knowledge of seasonal fluctuations in the degradation of the substance, acesulfame becomes an even more meaningful tracer.
"Our study shows that the seasonally fluctuating concentration of acesulfame can be used to better visualise and understand the processes in the subsurface, i.e. groundwater flows," said Hofmann. Wastewater components in drinking water can be recorded as well as the flow velocity of the groundwater and the mixing ratios of groundwater and river water. The environmental geoscientists evaluated river and groundwater samples that were collected regularly over eight years in a pre-alpine catchment. The research team linked their analyses to computer models that calculate water flows in the subsurface. "Such computer models are the key to risk prevention, because they can be used to understand how much river water and how much groundwater end up in the population's drinking water and how to optimise the operation of waterworks," added the head of the research group.
The sweetener acesulfame thus lays a tracer trail from wastewater to river and groundwater and finally to our drinking water. "The fact that acesulfame is not degraded is basically a good thing for us hydrogeologists because we can draw valuable information from it," says Hofmann. He adds: "However, this fact also makes us aware of our lifestyle being reflected in the wastewater and thus also in the drinking water: The sugar substitute we consume ends up back in our drinking water - albeit heavily diluted, of course," Hofmann said. (ANI)