Comparison of Some Filtration Processes Appropriate for Giardia Cyst Removal

摘要

Slow sand filtration, diatomaceous earth (DE) filtration, and coagulation-filtration (including conventional treatment, direct filtration, and in-line filtration), have been evaluated for Giardia cyst removal at pilot plant and/or field scale. Properly designed and operated, the above process can attain 99 percent cyst reductions, or higher. The paper discusses relative advantages and disadvantages of the proceses, and factors that may result in success or failure of treatment. Slow sand filtration may be the most appropriate for small systems if the raw water is treatable. DE filtration is very effective for cyst removal, but removal of very small particles requires use of fine grades of DE or chemical preconditioning of DE. Coagulation-filtration has the greatest flexibility, and can remove 30 to 50% of THM precursor; also turbidity, microorganisms, and metals that can be precipitated before filtration.