Application of synthetic wastewater as substrate for production of extracellular polymeric substances in bioreactors for their use as bio-flocculants

Abstract

An effective wastewater treatment not only crucial for the protection of the environment but also for public health. This study proposes innovative methods for producing extracellular polymeric substances, by using synthetic wastewater composed of two different carbon sources, glycerol and volatile fatty acids. Bioreactors were inoculated with mixed microbial cultures using aerobic sludge from wastewater treatment plant and employed to evaluate and compared the production yields, obtained characteristics and their performance as natural flocculants. Previous studies have demonstrated that glycerol produces EPS suitable for bio-flocculation, while volatile fatty acids have not been extensively studied. This thesis aims to address this gap. The obtained results indicate that using synthetic wastewater and mixed microbial cultures can effectively produce EPS suitable for use as natural flocculants. Fresh EPS from the bioreactor fed with volatile fatty acids showed better flocculation performance, while downstream freeze-drying process enhanced the flocculation efficiency of glycerol-derived EPS. Despite achieving the primary objectives, variability in production yields and EPS characteristics overtime was observed and attributed to differences in operational conditions. Overall, this research highlights the potential of using waste streams from biodiesel and pulp industries for sustainable EPS production, contributing to water quality improvement and resource management. While significant progress has been made, further research is needed to optimize EPS production, understand the role of the presence of cations within EPS structure, and expand their applications.