Premium
Baffling efficiency insights gained from tracer studies at 32 Washington treatment plants
Author(s) -
Porter Russell L.,
Stewart Keith P.,
Feagin Nancy,
Perry Sam
Publication year - 2018
Publication title -
awwa water science
Language(s) - English
Resource type - Journals
ISSN - 2577-8161
DOI - 10.1002/aws2.1115
Subject(s) - tracer , structural basin , laminar flow , reynolds number , flow (mathematics) , hydrology (agriculture) , environmental science , flow velocity , geology , geography , mechanics , geomorphology , geotechnical engineering , meteorology , geometry , mathematics , physics , nuclear physics , turbulence
This article summarizes tracer studies performed at 32 water treatment plants in Washington State ranging from 5 to 5,400 gpm, with contact basins from 200 gal to 1.5 mil gal. Multiple tracer studies were performed at each plant. The goal of the tracer studies was to determine the baffling efficiency (BE) of each basin by determining T 10 /T, where T 10 is the time at which 10% of a tracer is measured at the outlet of a basin, and T is the hydraulic residence time. The tracer studies indicated that most facilities historically used BE values higher than what the tracer studies indicated for calculating compliance with disinfection regulations. The majority of the basins were rectangular, baffled basins. The tracer studies indicated that standard design parameters, such as length‐to‐width ratio, were not as accurate in predicting basin performance compared with calculating baffled channel cross‐sectional velocity. This effect was pronounced where cross‐sectional flow velocity was below the Reynolds laminar flow threshold. For circular, baffled basins, a relationship between cross‐sectional velocity and BE was also evident. The study also identified issues with plants having parallel, chlorine contact basins where uneven flow splitting between basins created an overall system BE less than the BE of individual basins.