Swedish researchers at the KTH Royal Institute of Energy Technology in Stockholm have developed a unique water treatment technology that separates pharmaceutical residue from wastewater, thus preventing chemicals used in drugs from entering rivers and other waterways and damaging wildlife.
The technology, called "membrane distillation," and uses district heating to remove drug residue from wastewater. The method was developed in collaboration with the Swedish Environmental Research Institute (IVL) and local water purification technology provider Scarab Development AB.
The technology is highly efficient, but so far it has only been developed to work on a relatively small scale. Andrew Martin, professor at the KTH's Institute of Energy Technology, explained the process. First, water is heated so that it evaporates and the vapor passes through a very thin hydrophobic membrane made of material similar to Goretex. Then it goes through an air gap, where it condenses onto a cold surface, turning into liquid again. Drug residues are thus collected on one side of the membrane, whereas purified water ends up on the other side. Martin notes that the technology does not require very high temperatures, so it is a relatively simple process.
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Removing drug residue from water is very important because its presence can affect waterway ecosystems, interfering with the growth of algae. However, even more importantly, chemicals used in the pharmaceutical industry are harmful to fish and cause behavioral changes. A recent study by Sweden's Umea University found that the presence of the antidepressant Oxazepam in the Fyris River, in central Sweden, made perch more antisocial and more active, which in turn made them an easy target for predators. An analysis revealed that the level of Oxazepam found in perch was in fact six times higher than that measured in the water.
Researchers testing the membrane distillation technique at Hammarby Sjˆstadsverket in Sweden ran water in which a level of 282 nanograms of Oxazepam per liter was measured through the system. After being treated in a conventional way, the level of drug residue remained practically unchanged, whereas after being treated with the membrane distillation system the level of Oxazepam dropped to less than two nanograms per liter.
Martin explained that the system entirely eliminates the vast majority of all 20th century-tested drugs, with the exception of residue of the antidepressant Sertraline, which could not be cleared entirely. He said that developers were working on some theories why this happened but have not managed to explain the fact. Researchers are now awaiting results from the next step in the development of the technique, which tested membrane distillation with drug residue levels that are nearly 10 times higher than previously tested.