Exploring aeration-associated energy savings at a conventional water reclamation plant

Aeration accounts for a large fraction of energy consumption at conventional water reclamation plants (WRPs). Older plants were designed when control techniques were relatively primitive and energy consumption was less of a concern. As a result, although process operations at older WRPs can satisfy effluent permit requirements, they can operate with excess aeration. In this study, we developed a wastewater process model to evaluate possible aeration savings at the Metropolitan Water Reclamation District of Greater Chicago Calumet WRP, one of the oldest plants in Chicago. Based on subsets of influent characteristics, we identified eight steady-state scenarios. We also identified transient scenarios that included high probability perturbations and more challenging but lower probability conditions. Results indicate that the Calumet WRP frequently operates with excess aeration. Effluent dissolved oxygen is the limiting parameter with respect to aeration saving and permit requirements. In a typical storm event, aeration could be reduced by up to 50%; even under low probability challenging perturbations, aeration can be decreased by 35% from current average levels and all permit requirements can be satisfied. Annual cost savings from cutting the aeration by 35% could be more than $1.2 million.