Disinfection and toxicological assessments of pulsed UV and pulsed-plasma gas-discharge treated-water containing the waterborne protozoan enteroparasite Cryptosporidium parvum

Jennifer Hayes, Dominik Kirf, Mary Garvey, Neil Rowan

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)

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 (16kV, 10pps) 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 32min 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 (0.8mg/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 90s of pulsing [UV dose of 6.29μJ/cm2] 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.

Original languageEnglish
Pages (from-to)325-337
Number of pages13
JournalJournal of Microbiological Methods
Volume94
Issue number3
DOIs
Publication statusPublished - Sep 2013
Externally publishedYes

Keywords

  • Cell culture-qPCR
  • Cryptosporidium parvum
  • Pulsed light
  • Pulsed-plasma gas-discharge
  • Toxicity
  • Water treatment

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