title: Evaluation of biotracers to monitor effluent retention time in constructed wetlands.
abstract: OBJECTIVE
  With concern surrounding the environmental impact of chemical tracers on the aquatic environment, this paper presents the initial evaluation of biotracers used to determine the effluent retention time, an important performance indicator, in a Free Water Surface Constructed Wetland.
  
  
  RESULTS
  Production of the biotracers, coliphage MS2, and the bacteriophage of Enterobacter cloacae and antibiotic resistant endospores of Bacillus globigii is described in detail. Their subsequent use in three separate tracer experiments - January, March and June (2000) - revealed the variability of retention time with respect to effluent flow. The biotracer MS2 showed the constructed wetland had a retention time of 8-9 h at a mean discharge of 0.9 l s-1, increasing to 10-12 h at a mean discharge 0.3 l s-1. A similar retention of 9-10 h at a mean discharge of 0.3 l s-1 was calculated for the Ent. cloacae phage. In contrast, use of endospores revealed considerably longer retention times at these mean discharge rates; 12-24 h and 36-48 h, respectively.
  
  
  CONCLUSIONS
  Biotracers could provide a useful and environmentally friendly technique to monitor effluent retention in constructed wetlands. At this stage the phage tracers appear particularly promising due to ease of isolation and recovery.
  
  
  CONCLUSIONS
  Initial results are encouraging and have highlighted the potential of biotracers as alternatives to chemical tracers, even in microbially-rich waters.
authors.affiliation: Department of Chemical and Biological Sciences, University of Huddersfield, Huddersfield, UK.
authors.forename: C J
authors.initials: CJ
authors.lastname: Hodgson
authors.forename: J
authors.initials: J
authors.lastname: Perkins
authors.forename: J C
authors.initials: JC
authors.lastname: Labadz
mesh_terms: D001407:Bacillus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D024881:Drug Resistance, Bacterial; D017753:Ecosystem; D016972:Enterobacter cloacae / Q000821:virology; D004784:Environmental Monitoring / Q000379:methods; D005618:Fresh Water / Q000382:microbiology* / Q000821:virology*; D017909:Levivirus / Q000302:isolation & purification; D009268:Nalidixic Acid / Q000494:pharmacology; D012293:Rifampin / Q000494:pharmacology; D012722:Sewage; D013171:Spores, Bacterial / Q000187:drug effects; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage; D009268:Nalidixic Acid; D012293:Rifampin