A full-scale study of Cryptosporidium parvum oocyst and Cryptosporidium-sized microsphere removals from swimming pools via sand filtration

Abstract

Removal of Cryptosporidium parvum oocysts and Cryptosporidium-sized microspheres was evaluated in full-scale swimming pools via high-rate sand filtration (31–34 m/h) with coagulation. Results showed that at least 90% of C. parvum oocysts and microspheres were removed by filtration with an initial dosage of coagulant B (1.56 mg/L), D (1.9 mg/L or 305 g/m2), or F (1.56 mg/L) from each swimming pool. Filtration with an initial dosage of coagulant E (0.1 mg·Al/L) achieved 82% C. parvum oocyst removal and 97% microsphere removal. Coagulants B and F had a tendency to overdose over time with continuous feeding (based on corresponding pilot-scale experiments) and did not consistently achieve removals greater than 90% in the full-scale trials. As high as 99% of C. parvum oocysts and 98% of microspheres were removed with a continuous dosage of coagulant D. Up to 98% (1.7 log) of C. parvum oocysts and 93% (1.1 log) of microspheres were removed by continuous dosing of coagulant E at 27 m/h. Consistent oocyst and microsphere removal by aluminum-based coagulants (D and E) was achieved under the tested swimming pool conditions.