Prevalence of Protozoa and Indicator Bacteria in Wastewater Irrigation Sources in Kathmandu Valley, Nepal: Cases from Kirtipur, Bhaktapur, and Madhyapur Thimi Municipalities

Abstract

Wastewater irrigation using sewage and water from polluted sources is widespread in Kathmandu Valley, Nepal. Data on the prevalence of pathogens in irrigation sources are important for assessing the health risks for both farmers and consumers. In this study, 13 and 15 water samples were collected during the rainy (September 2014) and dry (April 2015) seasons, respectively, from irrigation sources [river water (n = 17), sewage (n = 5), pond water (n = 3), canal water (n = 1), and effluent of a wastewater treatment plant (WWTP; n = 2)] in Kathmandu Valley. Based on fluorescence microscopy, all the analyzed samples (n = 19) tested positive for Giardia, whereas 68% tested positive for Cryptosporidium. In addition, indicator bacteria (Escherichia coli and total coliforms) were detected in all samples (n = 28), with significantly higher concentrations during the dry season than during the rainy season (t-test, p < 0.05). Indicator bacteria and protozoan concentrations were abundant in sewage and river water samples and comparatively less in the remaining samples. Positive correlations between indicator bacteria and protozoa concentrations suggested that E. coli and total coliforms could be considered as rough indicators of protozoa contamination of wastewater irrigation sources.

Assessing the infection risk of enteropathogens from consumption of raw vegetables washed with contaminated water in Kathmandu Valley, Nepal

“…Giardia and/or Cryptosporidium in these water sources has been found in previous studies (Haramoto et al 2011;Shrestha et al 2016aShrestha et al , 2016b. Contamination of these water sources might be due to the influx of untreated wastewater into them.…”

“…Escherichia coli , Giardia and Cryptosporidium concentrations in river and well water and other sources were taken from our previous study and also from the literature (Shrestha et al . , ; Haramoto et al . ).…”

“…; Shrestha et al . ). In addition to the practice of wastewater irrigation, the practice of vegetable washing by farmers prior to selling and again by consumers prior to consumption is prevalent (Shrestha et al .…”

“…; Shrestha et al . , ). Contamination of these water sources might be due to the influx of untreated wastewater into them.…”

“…Irrigating vegetables by pumping water from sewage and other polluted sources such as rivers is widespread in the Kathmandu Valley (Rutkowski et al 2007;Shrestha et al 2016a). In addition to the practice of wastewater irrigation, the practice of vegetable washing by farmers prior to selling and again by consumers prior to consumption is prevalent (Shrestha et al 2016c).…”