The Metropolitan Sewer District of Greater Cincinnati (MSDGC) is upgrading the secondary aeration systems of its three largest water resource recovery facilities (WRRFs). MSDGC serves a population of 800,000 and operates seven WRRFs with a combined daily average flow of 700,000 m3/d (184 mgd). Aeration systems typically account for 40% to 60% of the total energy consumed at most WRRFs. So, in addition to maintenance concerns with aging equipment, the principal driver for these upgrades is energy efficiency.
All three facilities replaced their aeration blowers and one facility replaced its coarse-bubble diffusers with fine-bubble ones. All three facilities also will receive new aeration control systems to operate as efficiently as possible based on dissolved oxygen (DO) demand. MSDGC contracted with Brown and Caldwell (Walnut Creek, Calif.) for the design of upgrades to the aeration systems.