Scientists from MENDELU’s Faculty of Agriculture are trying to replace the polymers used in wastewater treatment with natural-based substances. Photo credit: MENDELU.
Brno, 14 June (BD) – Wastewater treatment is a biological process carried out using many different chemicals. According to scientists from Mendel University (MENDELU), some of these could be replaced by substances of natural origin. The experts are investigating the additives used in sewage treatment plants to separate sludge. They are trying to replace so-called flocculants with compounds contained in coffee grounds and waste from wine production. Scientists are trying to eliminate certain chemicals, because the sludge is commonly used on agricultural land.
About 800,000 tons of untreated sewage sludge are produced in the Czech Republic annually. They contain a spectrum of inorganic and organic substances, and are a source of basic nutrients and trace elements. In practice, they are therefore used as fertiliser for agricultural land, in the reclamation of landfills, or are composted. Sludge is most often separated from wastewater in treatment plants using chemicals based on polyacrylamides, which are substances also used in the food industry or the construction industry, for example, to modify the properties of concrete.
Scientists from the MENDELU Faculty of Agriculture (AF MENDELU) are currently trying to replace these polymers with natural-based substances. “Part of the reason we are targeting flocculant change is that polyacrylamides form large clumps that prevent nutrients from being released into the soil when sludge is applied,” said Pavel Suchý, who works at the Institute of Agricultural, Food and Environmental Technology at AF MENDELU. “At the same time, the clumps can survive in the sludge for up to half a year without any decomposition.”
In addition, according to project leader Tomáš Vítěz, there is still not much research dealing with how specifically polyacrylamides affect the soil.
“We found several publications from Spain and the results were not entirely satisfactory. A huge amount of synthetic substances enter nature through flocculants, which can pose a risk,” he explains.
Based on previous research, the scientists singled out tannin, a substance contained in coffee grounds or perhaps also in waste from wine processing, as a promising alternative.
“Tannin is interesting to us because we have a lot of cafes and an active wine industry in South Moravia, so we can effectively use the waste that is produced here,” explained Suchý. “We also value tannin for its properties. For example, the fact that it can disrupt the cell and thus contributes to more efficient sludge drainage.”
This year, experts will test the usability of tannin in the laboratory, and would like to transfer the knowledge gained directly into operation. As part of the Czech Technology Agency project, scientists are preparing to cooperate with a Czech manufacturer of wastewater treatment plants for cities and municipalities.
According to Vítěz, it is essential that the resulting flocculant is not expensive and that there is enough of it on the market. “We have to offer a solution that is cost-competitive with current solutions,” he said.
In the future, the experts plan to extend the research to treat drinking water. Even in this case, coffee could play its role. “Iron or manganese is usually removed from drinking water for the sake of taste. And by the fact that tannins bind metals, the difficulty of treating such water could be economically reduced,” added Vítěz.
