Applying an anaerobic side stream reactor to return activated sludge for sludge reduction

In response to the increasing demand for sustainable and cost-effective wastewater treatment solutions, this thesis investigates the application of an Anaerobic Side Stream Reactor (ASSR) to the return activated sludge (RAS) stream for sludge reduction and enhanced process performance. The research was conducted as part of a master's program at TU Delft, with experimental work carried out using a laboratory-scale Sequencing Batch Reactor (SBR) coupled with an ASSR setup. The primary aim was to explore how recirculating waste activated sludge through alternating anaerobic and aerobic phases could promote microbial decay, reduce excess sludge production, and potentially enhance volatile fatty acids (VFA) generation for downstream nutrient removal. The study combined practical experimentation with dynamic modeling in BioWin to simulate process performance and validate findings. Comprehensive data analysis was conducted, focusing on chemical oxygen demand (COD) balance, biomass behavior, and nutrient dynamics. Emphasis was placed on understanding the influence of operational parameters and iron dosing on sludge minimization and biological process stability. This work contributes to the development of more efficient sludge management strategies in municipal wastewater treatment and offers insights into the integration of ASSR as a viable approach for resource recovery and energy-efficient plant operation.