Industrial wastewater, typically referred to as high-strength wastewater, is a major source of ‎water pollution due to its elevated organic content. High-strength organic wastewaters are ‎characterized by chemical oxygen demand (COD) concentrations greater than 4000 mg/L. ‎The effluents of these industries need to undergo biological treatment to remove the organic ‎matter. However, conventional biological treatment processes fail to stabilize high-strength ‎wastewater to regulatory limits. Aerobic treatment processes are not economically feasible for ‎the treatment of high-strength organic wastewater. Anaerobic processes suffer from low ‎growth rate of the microorganisms, high sensitivity to toxic loadings, fluctuations in ‎environmental conditions, and require post-treatment to bring the water quality within ‎regulations.

This work aimed at developing an upflow aerobic granular sludge bioreactor (UAGSBR) to ‎provide a downstream effective treatment process in order to combine the benefit of ‎anaerobic digestion (i.e., biogas production) with the benefit of aerobic treatment (i.e., better ‎removal of organics). Moreover, it is hypothesized that effluent of anaerobic treatment ‎provides a solubilized organic matter suitable for subsequent aerobic treatment because of its ‎reduced organic strength and enhanced amounts of nitrogen and phosphorus. The combined ‎system will overcome the limitations of both anaerobic and aerobic systems, such as long ‎treatment duration and low stability due to rapid bacterial growth, respectively. ‎

In this project, biogranulation, formed by the self-immobilization of microorganisms, was ‎employed as a novel technology in an upflow semi-pilot-scale bioreactor. These granules are ‎dense microbial communities packed with different bacterial species, which can achieve rapid ‎treatment for high volumes of wastewater in a smaller footprint when compared to ‎conventional biomass. Mechanisms of granule formation and stability considering influential ‎factors such as system start-up, organic loading rate, food-to-microorganisms ratio, and ‎nutrients addition were examined. Treatment efficiency, assessed in terms of organics and ‎nutrients (nitrogen and phosphorus) removal, was above 90%. The UAGSBR provides a ‎compact system for high-strength organics wastewater treatment (at 20-30% spatial footprint ‎of a conventional plant). ‎