Valorisation of sludge biomass obtained from civil and industrial wastewater treatment plants (WWTPs)

The increasing worldwide energy consumption, higher energy requirements for future, exhaustion of fossil fuel resources and global warming have driven researchers to utilize renewable sources such as biomass to meet energy demands. As of 2020 in Europe about 13 million tons of dry solids were produced annually by wastewater treatment plants (WWTPs) and only in few cases it is valorised from an energy point of view, thereby minimizing its environmental impact. The main aim of the PhD project was to explore experimental strategies to valorise the sludge biomass obtained from civil and industrial WWTPs. Several sludge treatment methods have been explored in this work to enhance sludge hydrolysis including mechanical, chemical, thermal, and hydrothermal treatments. The treatments were focused on destroying microbial cell structure and releasing organics and the effect of different treatments on sludge solubilization was investigated. Furthermore, an effort to valorise both the solid and liquid fractions of the hydrothermally treated samples were done. Point of interest was to use the solid fraction to estimate bioenergy potential while on the liquid, recovery of organic molecules was attempted. In addition to this, raw sludge was attempted to be valorised by subjecting it to pyrolysis experiments. A small part of the PhD research was also dedicated to studying the valorisation of brewer’s spent grains (BSG) which is by product of beer manufacturing process in Poland.