- Pilot-scale experiments were conducted to investigate the removal of C. parvum by contact granular filtration. The experiments indicated efficient transport of C. parvum oocysts and limitations posed by attachment conditions. The required 99% oocyst removal was achieved during the operable period. Insufficient 95% removal was attributed to a reduced amount of accumulated material at ripening stage. Coagulation, filter depth and run time were found to be important in the removal of C. parvum oocysts.