Leveraging Research Real World Experience to Clarify Phosphorus LOT with Ballasted Sedimentation

摘要

The limit of technology (LOT) for P removal has historically been understood to be 0.1 mg/L. However; numerous facilities are meeting and pushing the LOT, with the lowest limits in the 0.01-0.06 mg/L-P range (WERF, 2014). Lower footprint and lower headloss separation processes (relative to conventional deep bed filters) in this application now have a larger operational database than when the historical LOT was set. As footprint and headloss are significant constraints for the Danbury site, it was pertinent to reassess the LOT for ballasted sedimentation. Further, given schedule constraints; selections which could be made confidently without long-term pilot testing were also preferable. A comprehensive review of available literature and operational data at full scale plants was initiated to support these LOT assessments. This paper looks into existing literature and reviews data from 3 full scale facilities to assess the LOT of Phosphorus by single stage tertiary sand ballasted sedimentation. From the assessment of full scale operations a series of design and operational best practices are demonstrated and a reasonable LOT of 0.06 mg/L-P is determined if utilizing these best practices at Danbury.