Efficacy of the solar water disinfection method in turbid waters experimentally contaminated with Cryptosporidium parvum oocysts under real field conditions

Abstract

Summaryobjective To investigate the efficacy of the solar water disinfection (SODIS) method for inactivating Cryptosporidium parvum oocysts in turbid waters using 1.5 l polyethylene terephthalate (PET) bottles under natural sunlight.methods All experiments were performed at the Plataforma Solar de Almería, located in the Tabernas Desert (Southern Spain) in July and October 2007. Turbid water samples [5, 100 and 300 nephelometric turbidity units (NTU)] were prepared by addition of red soil to distilled water, and then spiked with purified C. parvum oocysts. PET bottles containing the contaminated turbid waters were exposed to full sunlight for 4, 8 and 12 h. The samples were then concentrated by filtration and the oocyst viability was determined by inclusion ⁄ exclusion of the fluorogenic vital dye propidium iodide.results After an exposure time of 12 h (cumulative global dose of 28.28 MJ ⁄ m 2 ; cumulative UV dose of 1037.06 kJ ⁄ m 2 ) the oocyst viabilities were 11.54%, 25.96%, 41.50% and 52.80% for turbidity levels of 0, 5, 100 and 300 NTU, respectively, being significantly lower than the viability of the initial isolate (P < 0.01).conclusions SODIS method significantly reduced the potential viability of C. parvum oocysts on increasing the percentage of oocysts that took up the dye PI (indicator of cell wall integrity), although longer exposure periods appear to be required than those established for the bacterial pathogens usually tested in SODIS assays.

Drinking Water Disinfection by Solar Radiation

“…However, longer exposure times appear to be required than those required for the bacterial pathogens [73].…”

Thermal Contribution to the Inactivation of Cryptosporidium in Plastic Bottles during Solar Water Disinfection Procedures

“…Taking into account the high temperatures recorded in turbid water samples contained in ordinary transparent polyethylene terephthalate (PET) bottles placed in direct sunlight during SODIS procedures to inactivate Cryptosporidium , 20 in the present study, we focused on the thermal contribution of incident solar radiation in the inactivation of C. parvum oocysts.…”

“…The water temperature inside the bottles was measured each hour with a thermometer (model HI 98509-1; Hanna Instruments, S.L., Eibar, Spain) and different temperature profiles were obtained for water turbidity levels of 0, 5, 100 and 300 nephelometric turbidity units and exposure times of 4, 8, and 12 hours. 20 The average temperature profile registered for water of different levels of turbidity was simulated in the laboratory in a dry block heat bath fitted with a lid to protect the samples from UV light (Uniequip GmbH, Dresden, Germany). Distilled water (1 mL) and 2 × 10 6 purified C. parvum oocysts were placed in microcentrifuge tubes (1.5 mL).…”

Removal of pathogenic bacteria from sewage-treated effluent and biosolids for agricultural purposes

“…SODIS-based technologies are an efficient approach for the reduction of pathogenic microorganism in the water due to high availability of solar radiation and sustainable nature of these water treatment methods (Gomez-Couso et al 2009). According to WHO (2002), SODIS depends on using transparent polyethylene terephthalate (PET) bottles and then exposing to the sun for a period between 4 and 8 h. Meierhofer and Wegelin (2002) recommended that PET bottles containing untreated raw water should be exposed to direct sunlight for at least 6 h. Bacteria, viruses, Giardia and Cryptosporidium cysts, and parasite eggs could be inactivated through the combination of ultraviolet radiation and elevated water temperature.…”