Approximately 20% of wastewaters globally do not receive treatment, whereas wastewater discharges are projected to increase, thereby leading to excessive water quality degradation of surface waters on a global scale. Increased treatment could help alleviate water quality issues by constructing more treatment plants; however, in many areas there exist economic constraints. Energy recovery methods including the utilization of biogas and incineration of biosolids generated during the treatment process may help to alleviate treatment costs. This study explores the potential for investments in energy recovery from wastewater to increase treatment levels and thus improve surface water quality. This was done by examining the relationships between nutrient over-enrichment, wastewater treatment, and energy recovery at a global scale using system dynamics simulation as part of the ANEMI integrated assessment model. The results show that a significant amount of energy can be recovered from wastewater, which helps to alleviate some of the costs of treatment. It was found that wastewater treatment levels could be increased by 34%, helping to offset the higher nutrient loading from a growing population with access to improved sanitation. The production of renewable natural gas from biogas was found to have the potential to prolong the depletion of natural gas resources used to produce electricity and heat. It is recommended that agricultural nutrient discharges be better managed to help reduce nutrient over-enrichment on global scale. To increase the utility of the simulation, a finer spatial scale should be used to consider regional treatment, economic, and water quality characteristics.
Keywords: Energy recovery; System dynamics; Wastewater treatment; Water quality; Water resources.