Scientists Are Testing The Use Of Coffee Grounds In Wastewater Treatment

Wastewater treatment is a biological process, but many chemicals are currently used. According to scientists from the Mendel University in Brno, some of them could be replaced by substances of natural origin. The experts focused on additives that are used in sewage treatment plants to separate sludge. They are trying to replace so-called flocculants with compounds contained in coffee grounds or waste from wine production. Scientists are trying to eliminate chemicals, among other things, because sludge is commonly applied to agricultural land.

About 800,000 tons of untreated sewage sludge is produced annually in the Czech Republic. They contain a spectrum of inorganic and organic substances, they are a source of basic nutrients and trace elements. In practice, they are therefore used as fertilizer for agricultural land, in the reclamation of landfills, or are often composted. Sludge is most often separated from wastewater in treatment plants by dosing chemicals based on polyacrylamides, which are substances also used in the food industry or the construction industry, where they are used, for example, to modify the properties of concrete.

Scientists from the Faculty of Agriculture are currently trying to replace these polymers with natural-based substances. “Part of the reason we are targeting a change in flocculants is that polyacrylamides form large clumps that prevent nutrients from being released into the soil when sludge is applied to the soil. At the same time, the clumps can stay in the sludge for up to half a year without any decomposition," pointed out Pavel Suchý, who works at the Institute of Agricultural, Food and Environmental Technology of AF MENDELU.

In addition, according to project leader Tomáš Vítěz, there is still not much research that deals 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 said.

Based on previous research, the scientists singled out tannin as a promising alternative. A substance that is contained in coffee grounds or perhaps waste from wine processing. "Tanin is interesting to us not only 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. 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," explained Suchý.

This year, experts will test the usability of tannin in the laboratory, and they would like to transfer the knowledge gained directly into operation. As part of the TAČR 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 also 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.