Evaluation of peroxymonosulfate addition as a strategy to enhance Cryptosporidium inactivation in solar water disinfection

Solar disinfection (SODIS) is a low-cost water treatment used in areas without access to safe water, with well-established efficacy against bacteria, but limited for virus and protozoa. Cryptosporidium parvum is a waterborne protozoan resistant to conventional water disinfection methods, representing a major challenge in public health. This study evaluates for the first time the enhancement of SODIS against C. parvum using peroxymonosulfate (PMS). Distilled and well water with different PMS concentrations, in the absence or presence of Fe 2+ , were spiked with C. parvum oocysts and exposed to simulated solar radiation at 40 °C for 6 h, directly and under a polyethylene terephthalate (PET), polypropylene (PP) and polymethylmethacrylate (PMMA) covers. Oocyst viability was evaluated by quantifying 70 kDa heat shock protein mRNA using reverse transcription qPCR. Results showed that PMS concentrations ≥0.5 mM, in the absence and presence of Fe 2+ , reached >4 logarithmic reduction (LR) in the oocyst survival when water was exposed uncovered. Under all plastic covers, >4 LR was achieved in the absence of Fe 2+ in well water. Toxicity assays with Daphnia magna showed that, in the presence of Fe 2+ , 0.5 mM PMS-treated well water under PP and PMMA covers caused only 10% mortality after 24 and 48 h. Overall, results demonstrated that the incorporation of PMS in SODIS procedures can effectively inactivate C. parvum oocysts and reduces exposure time.