Twenty-five representative water treatment plants were surveyed to compare
differences in microbial, physical, and chemical water quality of raw waters and
spent filter backwash waters (SFBWs). On the basis of the observed Giardia and
Cryptosporidium levels, it was determined that a recycle ratio of 5-10% would be
sufficient to minimize the impact of protozoa on ambient raw water. Using the
cell culture-polymerase chain reaction method, infectious Cryptosporidium oocysts
were observed in raw water and SFBW samples. The presence of particles in the
SFBW samples increased the potassium permanganate demand by a factor of 5.5 and
the chlorine dioxide demand by a factor of 4.0. However, the presence of
particles in SFBWs did not affect the inactivation of Cryptosporidium.
Conventional treatment of SFBW with polymers resulted in excellent removal of
turbidity, particles, and microorganisms. A backwashable depth filter can be used
in place of a conventional filter for control of Cryptosporidium in clarified
SFBW. Includes 29 references, tables, figures.
| Edition : | Vol. 93 - No. 5 |
| File Size : | 1
file
, 400 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 05/01/2001 |
