Ever since the dawn of industrialization, humanity has left its mark on the environment - regrettably almost always to the detriment of the planet. And although it was noted long ago that some of what is cast aside can actually be reused, sometimes several times over, it could be argued that what we all know as "recycling" has fallen out of fashion somewhat. Luckily, researchers remain undeterred. Determined to create a real-life flux capacitor, they are constantly developing new processes that allow us to retrieve more and more from used materials - even from seemingly unpromising waste products such as sewage sludge. After all, sewage sludge contains a lot of important materials that have, until now, been hard to come by.
Sewage sludge is a heterogeneous mixture consisting mainly of water, organic substances and nitrogen and phosphorus compounds. In Germany alone, industrial and municipal sewage treatment plants generate around two million metric tons in a year. Until recently, it was mostly incinerated or used for agricultural purposes. But Germany's Sewage Sludge Ordinance, which was amended in 2017, has since shaken things up, stipulating that in the medium term at least phosphorus must be recovered from sludge. A new ultrasound method developed by AQUATTRO GmbH - which is being tested and optimized as part of the BMBF's "UltraSep" collaborative project involving Fraunhofer UMSICHT and Wupperverbandgesellschaft für integrale Wasserwirtschaft (WiW) - may well help attain this goal. The project revolves around a cutting-edge and patented ultrasonic cavitation unit that produces various physical and chemical effects in the sewage sludge that break it down so it can subsequently be separated into different recyclable fractions. Once everything has run its course, the new procedure is said to provide fibers that are rich in cellulose, a nutrient-rich gel and an easily fermentable liquid - all of which can be put to good use.
Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT (46047 Oberhausen, Germany)