A new method for clearing organic pollutants from wastewater uses hydrogel granules made from polyvinyl alcohol (PVA), which function as a biological carrier for microorganism cultures. In May 2022, the invention landed the top prize in an annual innovation fair in Lithuania, the Technorama 2022 event.
It was developed by a team of researchers from Kaunas University of Technology (KTU). The granules function by decomposing the pollutants in question – a treatment method said to work up to five times faster than conventional approaches.
Explaining the relevance of the invention, the group cites the fact that urban-based hospitals and industries such as small-scale mining and motor garages often dump highly toxic chemicals and medical waste into the wastewater system. Pollutants pose a threat not only to human health and the ecosystem.
A European Commission report reveals that 95 per cent of wastewater in the EU is collected and 88 per cent is biologically treated. However, over 6 per cent is not sufficiently well treated to meet secondary biological treatment standards. According to Judita Švaikauskaitė, a young researcher at KTU, the increasing number of micropollutants in waste and surface water poses challenges for wastewater treatment plants around the world.
“Water quality in the European Union is being closely monitored and analysed. The wastewater treatment companies need to update their methods with up-to-date technologies. Ozonation and other oxidation methods, biological treatment, and membrane filtration are the advanced technologies used to remove pollutants from water. Also, to improve the efficiency of biological treatment various biological carriers are used,” says Švaikauskaitė.
Advanced water treatment technologies that help improve water quality faster, more efficiently and without major changes to existing plants’ infrastructure are in high demand.
The hydrogel granules, designed by a team of environmental scientists from the KTU Faculty of Chemical Technology, are made from polyvinyl alcohol (PVA). Sized 3-4 mm in diameter, each granule has a porous structure comprising macropores of up to 20 microns. This is an appropriate size to immobilise microorganisms and therefore it can serve as a biological carrier.
The use of PVA hydrogel granules in biological wastewater treatment technologies can increase the removal efficiency of pollutants by a factor of five compared to conventional activated sludge treatment.
“Inside the pores of the granules, cultures of microorganisms that decompose pollutants in wastewater can live. The network of pores in the PVA hydrogel granules ensures a constant supply of oxygen and nutrients to the bacteria inside the granules, thus creating a highly durable and efficient biological wastewater treatment system,” said Švaikauskaitė.
PVA hydrogel granules are mechanically stable and therefore suitable for long-term use. The bacteria play a significant role in this process – they use ammonia, phosphate, organic compounds, and other chemical substances as nutrient and energy sources. A wide spectrum of bacteria can be immobilised inside a gel granule. PVA hydrogel granules demonstrate great absorption capacities for organic micropollutants and pharmaceuticals.
“PVA hydrogel granules not only increase the efficiency of the biological wastewater treatment system but also have excellent sorption properties in removing residues of pharmaceutical substances and other micro-pollutants from wastewater,” said Švaikauskaitė.
The method was developed by Švaikauskaitė together with KTU Department of Environmental Technology researchers Inga Urniežaite and Vytautas Abromaitis.
The invention seemingly stood out among more than 70 teams who presented ideas at the Technorama’ 22 event, which included contributions related to fields such as food, health, the environment, defence, digital solutions, mobility, engineering, and an inclusive society.
“I am very pleased that the work of our team has been noticed and appreciated. Winning the prize crowns a long, not always easy, but very interesting journey and gives confidence in pursuing a scientific career,” said Švaikauskaitė, who has just graduated with a master’s degree in Environmental Engineering.