title: Disinfection and toxicological assessments of pulsed UV and pulsed-plasma gas-discharge treated-water containing the waterborne protozoan enteroparasite Cryptosporidium parvum.
abstract: We report for the first time on the comparative use of pulsed-plasma gas-discharge (PPGD) and pulsed UV light (PUV) for the novel destruction of the waterborne enteroparasite Cryptosporidium parvum. It also describes the first cyto-, geno- and ecotoxicological assays undertaken to assess the safety of water decontaminated using PPGD and PUV. During PPGD treatments, the application of high voltage pulses (16 kV, 10 pps) to gas-injected water (N2 or O2, flow rate 2.5L/min) resulted in the formation of a plasma that generated free radicals, ultraviolet light, acoustic shock waves and electric fields that killed ca. 4 log C. parvum oocysts in 32 min exposure. Findings showed that PPGD-treated water produced significant cytotoxic properties (as determined by MTT and neutral red assays), genotoxic properties (as determined by comet and Ames assays), and ecotoxic properties (as determined by Microtox™, Thamnotox™ and Daphnotox™ assays) that are representative of different trophic levels in aquatic environment (p<0.05). Depending in part on the type of injected gas used, PPGD-treated water became either alkaline (pH ≤ 8.58, using O2) or acidic (pH ≥ 3.21, using N2) and contained varying levels of reactive free radicals such as ozone (0.8 mg/L) and/or dissociated nitric and nitrous acid that contributed to the observed disinfection and toxicity. Chemical analysis of PPGD-treated water revealed increasing levels of electrode metals that were present at ≤ 30 times the tolerated respective values for EU drinking water. PUV-treated water did not exhibit any toxicity and was shown to be far superior to that of PPGD for killing C. parvum oocysts taking only 90 s of pulsing [UV dose of 6.29 μJ/cm(2)] to produce a 4-log reduction compared to a similar reduction level achieved after 32min PPGD treatment as determined by combined in vitro CaCo-2 cell culture-qPCR.
authors.affiliation: Bioscience Research Institute, Athlone Institute of Technology, Dublin Road, Athlone, Ireland.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hayes
authors.forename: Dominik
authors.initials: D
authors.lastname: Kirf
authors.forename: Mary
authors.initials: M
authors.lastname: Garvey
authors.forename: Neil
authors.initials: N
authors.lastname: Rowan
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D020552:Comet Assay; D016785:Cryptosporidium parvum / Q000187:drug effects / Q000302:isolation & purification / Q000528:radiation effects; D004249:DNA Damage / Q000187:drug effects; D004203:Disinfection / Q000379:methods*; D056945:Hep G2 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010126:Ozone; D058626:Plasma Gases / Q000494:pharmacology; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry / Q000469:parasitology / Q000494:pharmacology; D018508:Water Purification / Q000379:methods*
chemical_list: D058626:Plasma Gases; D014867:Water; D010126:Ozone
keywords: Cell culture-qPCR; Cryptosporidium parvum; Pulsed light; Pulsed-plasma gas-discharge; Toxicity; Water treatment