The three-cell, 6-acre aerated lagoon at the Remsen (Iowa) Wastewater Treatment Plant could not meet new ammonia permit levels of less than 4 mg/l in winter and 2 mg/l in summer. The lagoon averaged 14 mg/l in summer and 27 mg/l in winter.
Each 12-foot-deep cell held 5 million gallons, but the primary cell had six feet of sludge in areas. “We were losing quite a bit of detention time and had no idea because we didn’t use a Sludge Judge (Nasco),” says chief operator Mike Ruden.
The complete-mix cell had 20 submerged coarse-bubble diffusers and the partial-mix cell had four, but
