Students find reeds could flush out harmful drug residue from water
Miniature wetlands at hospitals could be the answer to removing pharmaceuticals from wastewater that present a danger to the environment
The master’s students constructed a miniature wetland at AZ Groeninge teaching hospital in Kortrijk, using the natural filtration properties of reeds to help purify the building’s wastewater.
Medications that humans ingest – such as anti-inflammatories, narcotics and antibiotics – are not always fully absorbed by the body, meaning they end up in the wastewater system. Existing water treatment plants are not capable of removing all the residues, and they can go on to cause damage to plants and animals in rivers and seas.
Professor Diederik Rousseau, who supervised the students’ theses, said the contamination did not apply to drinking water, which goes through extra processes to remove the drugs.
While reeds have long been recognised as an efficient water filter, students Laurens Hubau and Lize Vanseveren set out to discover more about how the plants and their cleansing bacteria could cope with drug residues, about which information was lacking.
They found that although the reeds could not filter all traces of drug residues, a second step using ozone enabled them to complete the process.
“What we actually found is that the technologies are, for some pharmaceuticals, complementary,” Rousseau said. “Some pharmaceuticals are removed by the wetland but not by ozonation, and vice versa. So the combination gives more guarantees for good water quality.”
Reed beds blend in to the environment and are easier and cheaper to use than conventional treatment plants, he added.
The team worked with an innovative type of wetland, licensed by Rietland, a company based in Minderhout, Antwerp province, which was aerated with an additional oxygen supply. This extra efficiency gave it a much smaller footprint than regular wetlands, which usually occupy a large area.
The five-month trial involved filling a portable container with gravel and planting it with reeds, with an attached “settling tank” that removed coarse particles from the wastewater.
Some pharmaceuticals are removed by the wetland but not by ozonation, and vice versa
An initial test of the wastewater showed residues of beta-blockers, anti-inflammatories, anticonvulsants, narcotics, antacids and antibiotics. After the reed filtration, most traces were gone but some non-biodegradable substances remained, such as the widely used anti-inflammatory medication diclofenac.
A solution devised by Ghent professor Stijn Van Hulle was to treat the water again with ozone, which can be produced on site. But given the high electricity consumption needed to generate the ozone, Rousseau said they would look at ways to better control the dosage.
A study by Egina Malaj, one of Van Hulle’s former master’s students, reported that organic chemicals – which includes drug residues as well as pesticides, paints and other substances – “threaten the ecological integrity and biodiversity of almost half of the water bodies on a [European] scale”.
Rousseau said exposure to low concentrations of chemicals would not kill flora and fauna, but could have “minute effects in their body over time” by, for example, disrupting the balance of hormones.
He added that while there were currently no European standards for treating drug residues in wastewater, Switzerland had recently adopted new legislation and the European legislator was looking at the issue.