Removing Giardia and Cryptosporidium by conventional treatment and direct filtration

A two-year evaluation of Giardia cyst and Cryptosporidium oocyst removal was conducted at a full-scale 900-gpm water treatment plant and at a 0.5-gpm pilot plant, both operated under conventional treatment and direct filtration regimes. Raw water quality (turbidity and algal content), as well as treatment effectiveness in removing turbidity, controlled the removal of seeded cysts more than the mode of treatment. A high correlation was found between cyst removal rates and removal of the respective size particles; poorer correlation was found between the cysts and turbidity removal, whereas no correlation was established between the removals of cysts and heterotrophic bacteria.

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