title: Bacteria and disinfection byproducts in water from southern Mexico City.
abstract: Disinfection byproducts and microorganisms present in drinking water may have deleterious effects on human health. The authors examined bacterial indicators (enterobacteria and Helicobacter pylori [H. pylori]), physicochemical parameters, and trihalomethane (THM) levels to conduct a water quality evaluation in Mexico City, where little is known about disinfection byproducts and microbial counts. Analyses were performed by standard membrane filtration for the enumeration of total coliforms, fecal coliforms, fecal streptococci, and Vibrio species. Other testing consisted of polymerase chain reaction (PCR) for H. pylori, physicochemical parameters by selective electrodes, and THMs by head-space with the use of a gas chromatograph. Indicator bacteria and enterobacteria were detected in 23% of samples, with significant differences between total coliforms, fecal coliforms, and fecal streptococci before and after chlorination. H. pylori was detected in 69% of samples prior to chlorination and 57% postchlorination. THM levels were < 200 microg/l. Chlorine concentrations ranged from < 0.05 mg/l to 35 mg/l. Disinfection at the well does not ensure good water quality for the Mexico City population. The next step will be the monitoring of water quality in the distribution system that supplies dwellings, as well as water obtained directly from the tap.
authors.affiliation: Institute of Ecology, National Autonomous University of Mexico, University City, Mexico, DF. mazari@servidor.unam.mx
authors.forename: Marisa
authors.initials: M
authors.lastname: Mazari-Hiriart
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Lopez-Vidal
authors.forename: Sergio
authors.initials: S
authors.lastname: Ponce de Leon
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Castillo-Rojas
authors.forename: Cristina
authors.initials: C
authors.lastname: Hernandez-Eugenio
authors.forename: Francisco
authors.initials: F
authors.lastname: Rojo
mesh_terms: D002713:Chlorine / Q000032:analysis*; D002947:Cities; D015169:Colony Count, Microbial; D004203:Disinfection; D016480:Helicobacter pylori / Q000302:isolation & purification; D006801:Humans; D008800:Mexico; D014733:Vibrio / Q000302:isolation & purification; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification; D014881:Water Supply
chemical_list: D014874:Water Pollutants, Chemical; D002713:Chlorine