Bacteria remove pharmaceutical residue from waste water

Medicine not ingested by the body is flushed out with the urine and therefore ends up as a component in waste water. Over the coming year, the purification plant in Herning, Denmark, is to test whether bacteria can remove unwanted pharmaceutical residue from the waste water, and thus prevent it from entering the aquatic environment, where it may affect the fauna the live in lakes and watercourses. The test purification system is being applied in a large pilot facility set up at the Herning Vand plant in April.

Herning Vand is keen to be one step ahead of the situation when it is to deal with waste water from the new super-hospital in Gødstrup in around 2019. However, the issue is actually of interest to all waste water treatment plants, given that the sector estimates that approx. 95 per cent of all pharmaceutical residue in waste water stems from private households.

“We believe that over the coming year, the test set-up will clarify the extent of the issue of pharmaceutical residue in our local waste water. In addition, we expect to build up experience with the new method for purifying waste water, such that we will be in a position to provide responsible waste water management when the new super-hospital opens its doors,” says Niels Møller Jensen, CEO of Herning Vand.

​Small pilot plant with three MBBR reactors. Photo: Ravi Chhetri

The technology behind the experiment is simple and based on what is known as a ‘Moving Bed Biofilm Reactor’ (MBBR). This involves pouring a huge number of small, wheel-shaped plastic components—called ‘biocarriers’—with a diameter of around 2 cm into the water to be purified. These small biocarriers are designed precisely not to sink to the bottom of the tank, but to float around in the water.

On account of their large surface area, bacteria can establish a ‘foothold’ on them without risking being washed off. The waste water is then led through three tanks filled with biocarriers. In the first tank, the bacteria deal with the readily degradable pharmaceutical residue, which comes from analgesics such as Ibuprofen.

Specialist bacteria
The next tank houses more specialist bacteria, which can ‘eat’ the pharmaceutical residue that is harder to break down. By the time the waste water reaches the final tank, only the most resilient substances remain—so the tank contains biocarriers loaded with specialist bacteria culture to deal with them. While the bacteria cannot remove the pharmaceutical residue completely, they can purify the water to such an extent that costs for the subsequent purification process—which is highly energy intensive—can be reduced by around 30 per cent.

Technology involving biocarriers has been used for many years to remove undesirable substances from industrial waste water, but it was Associate Professor Henrik Rasmus Andersen from DTU Environment who came up with the idea of checking whether it could also be used to remove pharmaceutical residue. The pilot system ran for just under a year at Skejby Hospital before being moved to the Herning Vand facility. During the test processes, DTU Environment is responsible for testing purification using the MBBR method:

“The current test period is intended to provide us with additional operational experience and, at the same time, allow us to calculate accurately what it would cost to build a full-scale purification plant designed to use MBBR technology to remove pharmaceutical residue from waste water,” concludes Henrik Rasmus Andersen.