Microbial contamination of drinking water from vending machines of Eastern Coachella Valley

Abstract

Drinking water quality from sources other than tap water is increasingly becoming a source of concern in many communities. Communities in the Eastern Coachella Valley (ECV), Riverside County, California, USA have raised concerns regarding bulk drinking water from water vending machines (WVMs) found in public vendors. To address concerns, we conducted microbiological contamination assessments of drinking water from WVMs in the ECV using heterotrophic plate counts (HPC), the presence of total coliforms using IDEXX technology, and real-time PCR (qPCR). We also measured temperature, pH, electrical conductivity, and free chlorine concentration. Twenty-five WVMs were sampled by using positively charged NanoCeram® filters in the field. Results indicated 32% of WVMs had total coliforms, and 21% had HPC above Environmental Protection Agency (EPA) requirements. Through qPCR, we found 81% of WVMs had Salmonella spp., Listeria monocytogenes, and Campylobacter jejuni, 76% had Enterococcus faecalis, and 90% had Pseudomonas aeruginosa. Results indicated most WVM samples we collected contained genetic material of pathogenic microorganisms and therefore, did not meet EPA drinking water standards. There is an urgency to enforce WVM maintenance through drain flushing, spigot cleaning, rust removal, filter replacement, and limits to physico-chemical parameters.