title: Comparative analysis of solar pasteurization versus solar disinfection for the treatment of harvested rainwater.
abstract: BACKGROUND
  Numerous pathogens and opportunistic pathogens have been detected in harvested rainwater. Developing countries, in particular, require time- and cost-effective treatment strategies to improve the quality of this water source. The primary aim of the current study was thus to compare solar pasteurization (SOPAS; 70 to 79 °C; 80 to 89 °C; and ≥90 °C) to solar disinfection (SODIS; 6 and 8 hrs) for their efficiency in reducing the level of microbial contamination in harvested rainwater. The chemical quality (anions and cations) of the SOPAS and SODIS treated and untreated rainwater samples were also monitored.
  
  
  RESULTS
  While the anion concentrations in all the samples were within drinking water guidelines, the concentrations of lead (Pb) and nickel (Ni) exceeded the guidelines in all the SOPAS samples. Additionally, the iron (Fe) concentrations in both the SODIS 6 and 8 hr samples were above the drinking water guidelines. A >99% reduction in Escherichia coli and heterotrophic bacteria counts was then obtained in the SOPAS and SODIS samples. Ethidium monoazide bromide quantitative polymerase chain reaction (EMA-qPCR) analysis revealed a 94.70% reduction in viable Legionella copy numbers in the SOPAS samples, while SODIS after 6 and 8 hrs yielded a 50.60% and 75.22% decrease, respectively. Similarly, a 99.61% reduction in viable Pseudomonas copy numbers was observed after SOPAS treatment, while SODIS after 6 and 8 hrs yielded a 47.27% and 58.31% decrease, respectively.
  
  
  CONCLUSIONS
  While both the SOPAS and SODIS systems reduced the indicator counts to below the detection limit, EMA-qPCR analysis indicated that SOPAS treatment yielded a 2- and 3-log reduction in viable Legionella and Pseudomonas copy numbers, respectively. Additionally, SODIS after 8 hrs yielded a 2-log and 1-log reduction in Legionella and Pseudomonas copy numbers, respectively and could be considered as an alternative, cost-effective treatment method for harvested rainwater.
authors.affiliation: Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa.
authors.forename: André
authors.initials: A
authors.lastname: Strauss
authors.affiliation: Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa.
authors.forename: Penelope Heather
authors.initials: PH
authors.lastname: Dobrowsky
authors.affiliation: Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa.
authors.forename: Thando
authors.initials: T
authors.lastname: Ndlovu
authors.affiliation: Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa.
authors.forename: Brandon
authors.initials: B
authors.lastname: Reyneke
authors.affiliation: Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa. wesaal@sun.ac.za.
authors.forename: Wesaal
authors.initials: W
authors.lastname: Khan
mesh_terms: D058491:Bacterial Load; D003906:Developing Countries; D004203:Disinfection / Q000191:economics / Q000295:instrumentation / Q000379:methods*; D060766:Drinking Water / Q000032:analysis / Q000382:microbiology / Q000592:standards; D004784:Environmental Monitoring; D004926:Escherichia coli / Q000254:growth & development; D061352:Pasteurization / Q000191:economics / Q000295:instrumentation / Q000379:methods*; D011891:Rain; D013472:Sunlight; D014871:Water Microbiology; D018508:Water Purification / Q000191:economics / Q000295:instrumentation / Q000379:methods*
chemical_list: D060766:Drinking Water
keywords: EMA-qPCR; Legionella spp.; Microbial Indicators; Pseudomonas spp.; Solar Disinfection; Solar Pasteurization