New technology enables removal of multi-resistant bacteria from hospital wastewater before it reaches the treatment plant and can pose a risk to humans and the environment.
During the past two years, a partnership between DTU, the Danish Technological Institute, three utilities, and the technology supplier Norlex Systems—now called Alumichem—has developed a technology that can remove antibiotic-resistant bacteria from hospital wastewater in an environmentally friendly way. Removing multi-resistant bacteria already at the hospitals reduces the health risk for especially sanitation workers and employees in the treatment plants that receive the wastewater. Fewer resistant bacteria in the wastewater will also be significant if the sewers overflow in connection with heavy downpours.
The new technology uses the chemical peracetic acid, which is also used as a disinfectant in the food industry and in hospitals. Peracetic acid is completely degraded in water and thus poses no environmental risk. Instead, it has been shown to be able to remove antibiotic-resistant bacteria in wastewater.
“Together, we’ve developed a unique solution that removes antibiotic-resistant bacteria in an eco-friendly manner. The technology can be used both in separate sewer lines—as new hospitals often have—and in the solutions in which the wastewater from typically older hospitals is quickly led into the rest of the sewer network,” says Professor Henrik Rasmus Andersen, DTU Environment, who heads the project, and researcher Ravi K. Chhetri, who has been responsible for part of the laboratory tests and the analysis work behind the new solution.
Pilot test at two hospitals
The project has performed pilot tests at two different hospitals: Hillerød and Slagelse, each with its own sewer solution. This has been done using a pilot plant built in a container and thus easy to move.
The container has made it possible to take samples of wastewater during the process, so that the effect of different dosage levels of peracetic acid could be tested and compared with the time factor. If hospital wastewater is mixed with other wastewater already after one minute, a greater concentration of peracetic acid is necessary than if a separate sewer line means that the wastewater only mixes with the wastewater in the rest of the sewer network after half an hour.
Treatment plant ready for sale
The company Alumichem has handled the practical construction of the pilot plant. Alumichem supplies treatment plants to industrial companies that remove—for example—oil or chemicals from their wastewater before it is discharged into the sewer network. In future, the company can also supply plants to hospitals.
“Based on the project, we can adapt the solutions to the different needs of hospitals and municipal treatment plants. Several Danish municipalities have already shown an interest, and we know that there’s also an increasing need abroad to clean wastewater from hospitals,” says Technical Manager Thomas Eilkær, Alumichem.
In fact, Hillerød Forsyning has no doubt about the value of the project results. In connection with the new super hospital—which will be built in the city—a separate sewer line has thus been planned.
“The hospital will be a major point source for resistant bacteria in wastewater, and we now have the technological solution for how we can remove them from hospital wastewater before they’re mixed with the other wastewater of the city,” says Jørgen Skaarup, Planner in Hillerød Forsyning.
Important contribution to establishing guidelines
Antibiotic-resistant bacteria are not only found in hospital wastewater, as large quantities of antibiotics are consumed at home, thus ending up in household wastewater. As part of the project, the Danish Technological Institute has therefore—together with the utilities—gathered knowledge about the level of the content of antibiotic-resistant bacteria in Danish wastewater in general. This has been done by analysing more than 70 samples from 20 treatment plants.
These figures may be significant in relation to an upcoming recommended threshold for the content of antibiotic-resistant bacteria in wastewater from hospitals.
“Some of the new hospitals are working with solutions that remove all antibiotic-resistant bacteria from their wastewater. This is very expensive and perhaps it isn’t necessary for the threshold to be zero. It may instead be more logical for the authorities to require that the level be reduced to that found in ordinary household wastewater,” says Scientific Manager Caroline Kragelund Rickers, Danish Technological Institute.
Next focus is pharmaceutical residues
The next step for the researchers will be to examine the extent to which peracetic acid removes pharmaceutical residues from wastewater.
“We’ve seen in the project that there’s an effect, but we haven’t yet finished the necessary analyses that can quantify the potential. We’re looking forward to examining this further in the coming period,” says Ravi K. Chhetri.