Strategies for addressing increasing organic load in activated sludge units without increasing reactor volume

This thesis aims to explore and evaluate strategies that can be implemented in activated sludge processes to manage increasing pollution loads without expanding reactor volumes. Focusing on the optimization of the activated sludge process, which is of great importance for sustainable water management and environmental protection, the study emphasizes the significance of operational, biological, and chemical process optimizations, as well as advanced technologies and innovative approaches, for reducing energy consumption, lowering operational costs, and enhancing process efficiency. Conducted through an extensive literature review, this work examines the operational challenges encountered in activated sludge units, the impacts of increasing pollution loads, and innovative approaches proposed as solutions to these issues. The findings reveal the environmental and economic benefits of strategies for effectively managing pollution loads in wastewater treatment facilities without the need to increase their capacities. Moreover, the thesis highlights the need for future field studies and experimental data analysis to better understand the effectiveness and applicability of the proposed strategies in real-world applications. Dramatic increases in the immigrant population, unplanned expansion of industrial sectors producing organic pollutants in the city (e.g. food industry) or rapid growth of industrial zones may require expansion of wastewater treatment plants earlier than planned. There are various strategies that can be implemented before the volume of activated sludge units needs to be expanded in the face of increasing organic load. In this study, these strategies are discussed with a fictional wastewater example with an influent total COD concentration of 500 mg/L and a biodegradable COD concentration of 480 mg/L. In the modeling, the flow rate was increased from 1000 m3/day to 3000 m3/day. As the model shows, to cope with a threefold increase in organic load it may be necessary to increase the XSS (total suspended solids) concentration from 2 kg/m3 to 6 kg/m3 or reduce the sludge age from 8 days to 2 days, while keeping the reactor volume constant. Additionally, regardless of the model, approaches such as temperature control or membrane filtration appear to be available to increase the specific growth rate in the reactor. Each strategy is explained with points to consider during implementation.