Pilot studies were conducted to investigate the effect of recycling spent filter
backwash water (SFBW) on Cryptosporidium and particle removal during conventional
sedimentation and dual-media filtration. When SFBW recycle configurations
(3,000-19,000 oocysts/100 L) were used, Cryptosporidium concentrations in settled
water were as low as or lower than when no recycle was used (6,000-22,000
oocysts/100 L). Filtered water oocyst concentrations were typically below the
detection limit of 1 oocyst/120 gal (~0.25/100 L). Overall process removal was
about 5 log without recycle and about 5.7 log for each recycle scenario based on
calculations using raw Cryptosporidium concentrations and filtered water
detection levels. As with Cryptosporidium removal, removal of turbidity and
particles > 2 um for the entire process (sedimentation + filtration) was similar
for operations with and without recycle. Typical median filtered water
concentrations for particles > 2 um were < 0.5 particles/mL for all recycle
scenarios, including no recycle. Similarly, settled and filtered water turbidity
levels for all studies were typically < 2 and < 0.03 ntu, respectively. Includes 2 references, tables, figures.
| Edition : | Vol. 93 - No. 4 |
| File Size : | 1
file
, 330 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 04/01/2001 |
