AWWA JAW54010

Pilot studies were conducted to investigate the effect of recycling spent filterbackwash water (SFBW) on Cryptosporidium and particle removal during conventionalsedimentation and dual-media filtration. When SFBW recycle configurations(3,000-19,000 oocysts/100 L) were used, Cryptosporidium concentrations in settledwater were as low as or lower than when no recycle was used (6,000-22,000oocysts/100 L). Filtered water oocyst concentrations were typically below thedetection limit of 1 oocyst/120 gal (~0.25/100 L). Overall process removal wasabout 5 log without recycle and about 5.7 log for each recycle scenario based oncalculations using raw Cryptosporidium concentrations and filtered waterdetection levels. As with Cryptosporidium removal, removal of turbidity andparticles > 2 um for the entire process (sedimentation + filtration) was similarfor operations with and without recycle. Typical median filtered waterconcentrations for particles > 2 um were < 0.5 particles/mL for all recyclescenarios, including no recycle. Similarly, settled and filtered water turbiditylevels for all studies were typically < 2 and < 0.03 ntu, respectively. Includes 2 references, tables, figures.

Product Details

Edition:

Vol. 93 - No. 4

Published:

04/01/2001

Number of Pages:

10

File Size:

1 file , 330 KB