Effect of filter media on cyst and oocyst removal

Abstract

Spiking studies underscore the important role filtration plays in removing protozoa from surface water. As part of a pilot‐scale examination of filtration media at the Cincinnati (Ohio) Water Works, heat‐inactivated Giardia cysts and Cryptosporidium oocysts were spiked into surface water that had already undergone coagulation and sedimentation. This spiked water was then introduced into pilot‐scale filters containing sand only, typical dual anthracite–sand, and deep dual anthracite–sand media configurations. All of the media types used in this study demonstrated similar removal capabilities, with average cyst removal ranging from 2.7 to > 4.5 logs and average oocyst removal of 2.7–3.9 logs. Endospore and polystyrene bead removals were similar to those of the protozoa, but turbidity and particle counts demonstrated substantially less removal capability.

Association between the concentration of protozoa and surrogates in effluents of the slow sand filtration for water treatment

“…As a monitoring alternative, Swertfeger et al (23) consider that particle count and turbidity are more suitable to be used as real-time monitors -showing when the treatment may be compromised or whether immediate adjustments are necessary -than to determine process removal capacities.…”

“…Swertfeger et al (23) have also evaluated endospores, particle count, and turbidity as performance indicators in the removal of protozoa from artificially-contaminated water filtered in different filter media. The removal of endospores was slightly conservative compared with that of oocysts under both winter and summer conditions.…”

Fluorescence resonance energy transfer (FRET)‐based specific labeling ofCryptosporidiumoocysts for detection in environmental samples

“…FRET can be designed to have a large Stokes' shift; viz. the difference between the absorption and emission maxima (11,25), which is probably the most important feature to increase the sensitivity of a fluorescence detection method. Petit et al (25) suggested that the Stokes' shift should be at least 20 nm, and Vesey et al (26) showed that for any excitation wavelength of 300 -700 nm, the autofluorescence emission intensity decreased with increasing excitation.…”

“…For example, even though turbidity has been known to correlate with parasite removal (10), it can overestimate the performance of water treatment (11). Particle counting (4 -10-m range) shows more promise, but there are different correlations between removal of oocysts and particle counts for each source water type (10).…”

“…Lastly, fluorescent surrogates (fluorescent-dyes polystyrene microspheres) have been shown to correlate well with oocysts/cysts inactivation (14), and are potentially simpler and a more accurate indicator for assessing the treatment processes efficacy, especially ozo-nation (15). Though fluorescent microspheres may over predict oocysts removal, they are recommended when the public health concerns prevent the use of spiking with oocysts (11). Furthermore, problems in accurately measuring Cryptosporidium oocysts in waters can not be over stated despite improved methods such as US-EPA Method 1623 (16,17), so confounding many previously reported comparisons.…”