title: Interactions between humic matter and bacteria when disinfecting water with UV light.
abstract: OBJECTIVE
  To investigate the impact of aquatic humic matter on the inactivation of Escherichia coli and Bacillus subtilis by ultraviolet (UV) light.
  
  
  RESULTS
  A bench-scale study investigated the potential for Aldrich((R)) humic acid (AHA) and Suwannee River natural organic matter (SR-NOM) to coat the surface of E. coli and B. subtilis and offer protection from low-pressure UV light. UV doses of 5 and 14 mJ cm(-2) were applied using a collimated beam at four concentrations of humic matter (0, 10, 50 and 120 mg l(-1)) in reagent grade water. Both AHA and SR-NOM were found to offer statistically significant protection of both E. coli and B. subtilis at concentrations of 50 and 120 mg l(-1) for a UV dose of 14 mJ cm(-2).
  
  
  CONCLUSIONS
  Both E. coli and B. subtilis are susceptible to coating by humic matter which can reduce the sensitivity of the cells to UV light.
  
  
  CONCLUSIONS
  Micro-organisms in the environment may acquire characteristics through interaction with humic matter that render them more resistant to UV disinfection than would be predicted based on laboratory inactivation studies using clean cells.
authors.affiliation: Department of Civil Engineering, University of Toronto, Toronto, ON, Canada.
authors.forename: R E
authors.initials: RE
authors.lastname: Cantwell
authors.forename: R
authors.initials: R
authors.lastname: Hofmann
authors.forename: M R
authors.initials: MR
authors.lastname: Templeton
mesh_terms: D004203:Disinfection / Q000379:methods; D004926:Escherichia coli / Q000528:radiation effects* / Q000648:ultrastructure; D005374:Filtration; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D012722:Sewage; D014466:Ultraviolet Rays; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*
chemical_list: D006812:Humic Substances; D012722:Sewage