Filtration behaviors of Giardia and Cryptosporidium - Ionic strength and pH effects

The laboratory-scale filtration tests of Giardia cysts and Cryptosporidium oocysts in both 2 mm-Phi glass beads and 2 mm-Phi polystyrene beads filters were conducted to investigate their filtration behaviors. The protozoan pa rasites were used as target particles. while the chemical system altered by changing the electrolyte concentration and pH, The results significantly i ndicate that ionic strength have a positive effect on the removal efficienc ies for Giardia cysts and Cryptosporidium oocysts. The removal efficiency o f two filters for Giardia cysts slightly decreased from pH 2.4 to 8.7 and d ecreased significantly in pH as pH up to 8.7, while that for Cryptosporidiu m slightly rippled beyond pH 8.7, and with the decrease in pH up to pH 8.7. The experimental collision efficiencies from the interactions between coll oids and the filter media were calculated with a semi-empirical approach of the single sphere model and clean-bed filtration theory. The results also indicated that experimental collision efficiencies for (oo)cysts correspond ed to the (oo)cysts removal efficiencies in all trials, and oocysts exhibit s higher collision efficiencies than cysts. (C) 2001 Elsevier Science Ltd. All rights reserved.