For many of us, the period of typical autumn diseases is associated with antibiotics. The scientists warn: antibiotics must be used reasonably. Through waste water, residues of medicines enter the environment. Researchers at STU are developing the methods of removing the residues of medicines, drugs, viruses, and antibiotic-resistant bacteria from water. They consider chemical forms of cleaning, use of nanodiamond layers, ferrates, photoactive powders, as well as the application of biological forms of aquatic plants. Some procedures will be protected by patents.
Team of the STU Faculty of Chemical and Food Technology monitors composition of the waste water entering and leaving wastewater treatment plants in several tens of the Slovak towns and eight hospitals. They examine presence of more than 30 types of drugs and 120 type of medicines as well as antibiotic-resistant bacteria.
"Wastewater treatment plants are able to very effectively remove substances defined by the law, particularly the nitrogen-containing pollution such as ammonia, and organic contamination such as carbohydrates, fats and proteins. However, their efficiency is lower in case of micropollutants such as the above-mentioned drugs, pesticides, hormones and other substances. This is because the technology of water purification is about one hundred years old and has not changed significantly since then. Scientists are facing a new challenge, "says Tomáš Mackuľak of the Faculty of Chemical and Food Technology, leader of the research team.
The researchers carry out measurements in wastewater continuously throughout the year. Concentrations of substances vary: the winter and spring months mark elevated concentrations of antibiotics, while the concentrations of antihistamines is higher in the summer. Presence of antidepressants, drugs for cardiovascular diseases and high blood pressure is recorded throughout the year. As for drugs, measurements confirm popularity of marijuana and methamphetamine in Slovakia. Consumption of ecstasy increases in larger cities over weekends. Significantly higher, however, is consumption of 'legal drugs', cigarettes in particular.
The researchers also monitor presence of resistant bacteria, mainly those most common in the colon or on the skin, that are potentially pathogenic: enterococci, staphylococci and coliform bacteria, particularly Escherichia coli and Staphylococcus aureus.
"Analysis of the wastewater flowing to the treatment plant revealed much higher amount of antibiotic resistant bacteria, compared to the waters running off the plant. High amount of resistant bacteria, however, was also recorded in the stabilized sludge. It is therefore worth considering how to dispose of the sludge. In some countries, similarly to Slovakia, sludge is processed to compost. In Germany, it is burnt, "explains Lucia Bírošová of the Faculty of Chemical and Food Technology, head of the team investigating resistant bacteria.
Combating antimicrobial resistance is a priority of the European Union. The latest research suggests that although we manage to kill bacteria, its DNA can survive in water for some time while sustaining the ability to resist antibiotics. The team of L. Bírošová intends to focus on the very ability of the bacteria DNA to survive in the water purified by some of the methods developed in STU.
The STU researchers examine several methods of cleaning and disinfecting water, starting with aquatic plants through chemical methods up to nanomaterials. They test application of graphene oxide and nanodiamond layers. "We are developing boron-doped diamond electrodes able to remove even most complex molecules such as medicines, pesticides, drugs or even resistant bacteria off the water. The new developed super-resistant materials are able to clean and disinfect, and, what is more, even to determine the presence of pollutants on the site of pollution, if necessary. Our nanodiamond electrodes could be then used to analyse substances in water, and also to detect the substances in blood and urine, "explains Marián Vojs of the STU Faculty of Electrical Engineering and Information Technology.
The use of ferrates seems to be very effective. "Ferrates can remove biological pollution, i.e. microbes or bacteria; besides, they can eliminate the life-threatening chemicals from water. Application of ferrates makes pollution oxidize, binding it to the surface, "explains Miroslav Gál of the STU Faculty of Chemical and Food Technology. The research team is currently looking for the ways to store ferrates. A 3D printer develops a suitable container resistant to the action ferrates, but dissolvable in water.
Chemical processes, i.e. radicals-based chemical oxidation or the use of aquatic plants, prove to be the cheapest ones. Such "root water treatment plants" can detain micropollutants; however, they cannot sufficiently remove resistant bacteria.
"Given the high costs of the methods developed so far, the approach to water treatment will probably change in the future: water will be treated directly on-site at the major polluters such as hospitals and medical institutions. In some countries, this is already happening: in case of major epidemics, waste water in sewage is disinfected directly at hospitals. However, limited use of antibiotics and medicines would be ideal. Unfortunately, too big amount of them are being prescribed in Slovakia, "says Mackuľak.