Hydraulic overloading and the need to meet dissolved oxygen (DO) requirements were constant concerns at the Lockport (Ill.) Wastewater Treatment Plant. Its ammonia nitrogen limit was 15 mg/l discharging into Deep Run Creek, and superintendent Joe Findlay had trouble keeping it below double digits. The DO hovered just above the permitted 6.0 mg/l.Enlarged three times since it opened in 1959, the facility consists of the original north plant and the south plant built in 2005. The latter had room for one final expansion, and the design work went to Robinson Engineering Ltd., South Holland, Ill. They selected a three-pass, plug
