Efficacy of a small-quantity water treatment method for inactivating Giardia cysts in raw water

CHLOROFLOC (Control Chemicals, Bramley, South Africa) is a commercial product developed for clarifying and disinfecting small quantities of raw water. It consists of a mixture of sodium dichloro-S-triazinetrione dihydrate as a source of chlorine for disinfection and a proprietary flocculant to clarify raw water. The efficacy of the disinfection process with regard to Giardia muris cysts was investigated. The ability of G. muris trophozoites to excyst under defined conditions was used as the criterion for viability before and after treatment. Experiments were performed using artificially polluted water at 25, 15, 10 and 53C. In each of these temperatures the time and dosage required to effect a 99.9% reduction in the number of viable cysts was determined. At 253C one tablet per litre was effective after 7 min., whereas at 15 and 103C the exposure time had to be extended to 15 min. At 53C, two tablets per litre and a 15 min. exposure time were required.