The Richmond Wastewater Treatment Facility was regularly meeting its permit limit of 1.0 mg/L effluent phosphorus.The only trouble was that doing so required the addition of alum, which had once cost about $250,000, upstream of the final clarifiers.To address that issue, the Richmond Sanitary District installed large-bubble mixing systems to create anoxic zones in selected aeration basins as part of a $14 million plant upgrade. The anoxic zones enable biological phosphorus removal and have nearly eliminated the feeding of alum.
CUTTING DOWN ON CHEMICALSThe city of Richmond lies in east-central Indiana next to the Ohio border. The sanitary district serves about
