Taking Denitrification to the Next Level: An Upgrade of Proven Technology With 21st Century I&C

In 2006 one of the largest water reclamation facilities in the northern Virginia recognized the need to expand the facility to support future population growth and to comply with new regulations. For this, Prince William County Authority (PWCSA) decided to simultaneously increase the flow capacity and the nutrient removal capabilities to the plant. At the same time, there was a need to replace their plant-wide data acquisition and control system (DACS) that was becoming obsolete.As part of this design-build project, the existing aeration basin volume was doubled and reconfigured; 14 new deep bed denitrification filters were implemented for a total of 24; and methanol feed to the filters was automated. Furthermore, a new modern supervisory control and data acquisition (SCADA) system was implemented.All this enhanced the operation and reliability of the process and also reduced the risk of methanol overdose by more closely matching the methanol feed to the actual demand. This plant is currently in full operation and in compliance with the effluent requirements. The integration of new technologies, the operational benefits, and the startup coordination required to reliably meet the new operating permit limits are described in more detail.