Occurrence and separation of Cryptosporidium oocysts in drinking water treatment

The presence of Cryptosporidium sp. in Czech drinking water sources was monitored. High numbers of Cryptosporidium oocysts were found in the Slezska Harta reservoir after 1997 summer floods. The influence of iron (III) coagulant dose, mixing conditions and preozonation on the removal efficiency of Cryptosporidium oocysts was studied. Low mixing intensity produced flocs with poor settling features. The efficiency of sedimentation expressed as residual iron after sedimentation was proportional to removal efficiency of oocysts. Both underdosing or overdosing of iron (III) coagulant resulted in decrease of COD, turbidity and oocyst removal. Preozonation positively influenced removal efficiency of oocysts in the conventional drinking water treatment train studied.