Effective depth controls the nitrate removal rates in a water supply reservoir with a high nitrate load.

The Occoquan Reservoir is part of an indirect potable reuse system where a water reclamation plant (WRP) discharges a nitrified product water to prevent the onset of anaerobic conditions in the bottom sediments during the summer months. The elongated narrow shape of the reservoir combined with water temperature gradients in the inlet results in density currents that enhance the transport of nitrate from the surface to the bottom waters. The morphology of the reservoir also causes a longitudinal change in the ratio of water volume to sediment area, herein defined as the effective depth (Z).

Effects of nitrate input from a water reclamation facility on the Occoquan Reservoir water quality.

To manage water quality in the Occoquan Reservoir, Virginia, a water reclamation facility discharges nitrified product water that reduces the release of undesirable substances (e.g., phosphorus, iron, and ammonia) from sediments during periods of hypolimnetic anoxia.