Spatial and Hydrologic Variation of Bacteroidales, Adenovirus and Enterovirus in a Semi-arid, Wastewater Effluent-Impacted Watershed

DUSTIN G. BAMBIC; BEVERLY KILDARE; VERÓNICA B. RAJAL; BELINDA MCSWAIN; CHRIS B. MINTON; ALEXANDER SCHRIEWER; STEFAN WUERTZ

WATER RESEARCH

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2015 vol. 75 p. 83 - 94

0043-1354

Bacteroidales and viruses were contemporaneously measured during dry and wet weatherconditions at a watershed-scale in a semi-arid watershed impacted by a mixture of agriculturalrunoff, municipal wastewater effluent and municipal runoff. The results highlightthe presence of municipal wastewater effluent as a confounding factor for microbial sourcetracking (MST) studies, and thus data were segregated into groups based on whether theywere impacted by wastewater effluent. In semi-arid environments such as the CalleguasCreek watershed, located in southern California, the relative contribution of municipalwastewater effluent is dependent on hydrology as storm events lead to conditions whereagricultural and municipal stormwater dominate receiving waters (rather than municipalwastewater, which is the case during dry weather). As such, the approach to data segregationwas dependent on hydrology/storm conditions. Storm events led to significant increasesin ruminant- and dog-associated Bacteroidales concentrations, indicating thatoverland transport connects strong non-human fecal sources with surface waters. Becausethe dataset had a large number of non-detect samples, data handling included the KaplaneMeir estimator and data were presented graphically in a manner that reflects the potentialeffect of detection limits. In surface water samples with virus detections, Escherichiacoli concentrations were often below (in compliance with) the recreational water qualitycriteria. In fact, sites downstream of direct inputs of municipal wastewater effluentexhibited the lowest concentrations of E. coli, but the highest concentrations of humanassociatedBacteroidales and highest detection rates of human viruses. The toolkit,comprised of the four Bacteroidales assays and human virus assays used, can be successfullyapplied to inform watershed managers seeking to comply with recreational waterquality criteria. However, care should be taken when analyzing data to account for theeffect of non-detect samples, sources with differing microbial viability, and diverging hydrologicconditions.