AWWA JAW28478

Diatomaceous earth filtration was evaluated for removal of Giardia muris, Cryptosporidium, turbidity, and coliform bacteria from a surface water. The effect of cationic polymers and alum on this removal was also investigated. Essentially all of the Giardia cysts and >99.9 percent of Cryptosporidium oocysts were removed from waters containing approximately 2,000 cysts/L. The removal of Cryptosporidium was further improved by using alum. Greater removals of coliforms and turbidity, especially small particles (3 um or less), were also achieved when chemical coagulants were added. Use of these chemicals reduced the length of filter runs, even for low-turbidity waters, because of higher head losses. Includes 14 references, tables, figures.