Removal of Giardia and Cryptosporidium in drinking water treatment: a pilot-scale study

Giardia and Cryptosporidium have emerged as waterborne pathogens of concern for public health. The aim of this study is to examine both parasites in the water samples taken from three pilot-scale plant processes located in southern Taiwan, to upgrade the current facilities. Three processes include: conventional process without prechlorination (Process 1), conventional process plus ozonation and pellet softening (Process 2), and integrated membrane process (MF plus NF) followed conventional process (Process 3). The detection methods of both parasites are modified from USEPA Methods 1622 and 1623. Results indicated that coagulation, sedimentation and filtration removed the most percentage of both protozoan parasites. The pre-ozonation step can destruct both parasites, especially for Giardia cysts. The microfiltration systems can intercept Giardia cysts and Cryptosporidium oocysts completely. A significant correlation between water turbidity and Cryptosporidium oocysts was found in this study. The similar results were also found between three kinds of particles (phi=3-5,5-8 and 8-10 microm) and Cryptosporidium oocysts.