A reactor, stable foam cubes, and microorganisms: these are the key components of the wastewater treatment plant that Prof. Dr.-Ing. Markus Röhricht and his student team need to purify wastewater. The plant is designed to operate on solar power during the day and remain idle at night. After conducting initial basic research in the laboratory of the Technische Hochschule Mittelhessen (THM), the team has been conducting practical experiments at the wastewater treatment plant in Lollar since September of this year.
EnsAK (Development of a novel, solar-powered wastewater treatment system for disaster situations) is the name of the research project, which is funded by the Federal Ministry for Research, Technology and Space with €242,500. It is scheduled to run for a total of two years. In addition to the project partners Saygin & Stein, THM , and EMW filtertechnik GmbH, the Lollar-Staufenberg Zweckverband (a special-purpose association) is an ideal project partner.
The small wastewater treatment plant currently operating in Lollar was set up by the company Saygin & Stein within just a few days, designed to function even in a disaster situation. THMstudent Louis Müller oversees and maintains the plant. He is studying for a Master's degree in Climate Protection, Environmental and Safety Engineering. He is on-site every two days, and if there are any problems, he is there daily. "The pre-treated wastewater from the treatment plant flows into the reactor. It has already been cleaned of coarse dirt in the screening building and passed through a grit and grease trap," Müller explains. He opens the reactor lid, and foam cubes swirl through the wastewater. Microorganisms have been inoculated onto the cubes. They form a biofilm that continuously regenerates itself. The sludge produced by the deteriorating biofilm settles in the secondary clarifier of the pilot plant. After that, the treated wastewater could be released back into a river. In Lollar, it passes through the treatment plant one more time.
“With our experimental wastewater treatment plant, we can already comply with the strict limit for organic pollutant load that applies to large wastewater treatment plants in Germany. This is measured as chemical oxygen and is reduced by 90 percent by our plant,” explains Professor Röhricht. Nitrogen in the wastewater, which harms waterways through over-fertilization, is already eliminated by 60 to 70 percent. The water treated in the reactor is regularly tested. Samples are taken on Sundays, Tuesdays, and Thursdays and sent to THMlaboratory as composite samples. This means that the wastewater from an entire twelve-hour cycle is collected in a sample container and then analyzed in the laboratory.
In new series of experiments at the THMlaboratory, which are running in parallel, the research team aims to determine how the residence time of the wastewater in the reactor can be reduced from the current 16 hours to approximately ten hours. Another goal is to be able to use fewer cubes. These currently make up about 30 percent of the reactor volume, as Röhricht explains.
Biotechnology student Nicolas Jost is currently investigating different materials for the cubes in the lab, both fine-pored and coarse-pored materials. He is also conducting an experiment with a higher wastewater load. He will write his master's thesis on this topic.
The pilot plant in Lollar is designed to run a full year to determine how well the wastewater is treated at varying temperatures. After the trial, the optimized plant should be deployable wherever crises or wars create emergency situations for people.
Further information about the project can be found in the press release from September 2024 .