AWWA WQTC57063

No scientific database is available to guide utilities in determining the appropriate flushing velocity that will create a shear force capable of dislodging and transporting specific types of particles, film, or scale. Often, criteria used to decide when flushing is adequate include visual observation of "clear" water coming from the hydrant, a pre-selected time period (sometimes related to calculations on volume of water displaced), the ability of the zone to maintain pressure, or samples collected and analyzed for standard water quality analyses. On-site water quality analyses may be valid indicators of effective flushing but still leave the estimated velocity, duration, and frequency of flushing to guesswork or generalization. The stated objective of this project was to determine the range of flushing velocities required to dislodge and remove various accumulated materials from water distribution mains. The project approach was broken into five tasks: an evaluation of existing information through a literature review, utility survey, and utility case studies; characterization of accumulated materials; pilot studies including computational fluid dynamics (CFD) modeling and two pipe rigs; field testing; and, development of site-specific velocity recommendations. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2002

Number of Pages:

19

File Size:

1 file , 470 KB