Tracking Fecal Bacterial Dispersion from Municipal Wastewater to Peri-Urban Farms during Monsoon Rains in Hue City, Vietnam.

Windra Prayoga,Hieu Van Duong,Lieu Khac Pham,Toru Watanabe,Dung Viet Pham,Loc Thi Thanh Dang,Susan Praise,Masateru Nishiyama

doi:10.3390/ijerph18189580

Windra Prayoga, Hieu Van Duong + Show 6 more

Open Access

https://doi.org/10.3390/ijerph18189580

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Abstract

Disease outbreaks attributed to monsoon flood-induced pathogen exposure are frequently reported, especially in developing cities with poor sanitation. Contamination levels have been monitored in past studies, yet the sources, routes, and extents of contamination are not always clear. We evaluated pollution from municipal wastewater (MWW) discharge and investigated fecal contamination by Escherichia coli (E. coli) in three agricultural fields on the outskirts of Hue City, Vietnam. After E. coli concentration was determined in irrigation water (IRW), MWW, soil, vegetables (VEG), and manure, its dispersion from MWW was tracked using multilocus sequence typing (MLST) and phylogenetic analyses during the wet and dry seasons. IRW was severely contaminated; 94% of the samples were positive with E. coli exceeding the stipulated standards, while VEG contamination was very low in both seasons. The confirmed total number of isolates was comparable between the seasons; however, results from MLST and phylogenetic clustering revealed more links between the sites and samples to MWW during the wet season. The wet season had four mixed clusters of E. coli isolates from multiple locations and samples linked to MWW, while only one mixed cluster also linking MWW to IRW was observed during the dry season. The most prevalent sequence type (ST) complex 10 and two others (40 and 155) have been associated with disease outbreaks, while other STs have links to major pathotypes. Irrigation canals are significant routes for E. coli dispersion through direct links to the urban drainage-infested river. This study clarified the genotype of E. coli in Hue city, and the numerous links between the samples and sites revealed MWW discharge as the source of E. coli contamination that was enhanced by flooding.

Highlights

Municipal wastewater samples were taken from a wastewater drainage pipe in the Toa Kham (TK) area of Hue City, while irrigation water (IRW), SOL, VEG, and MNR samples were collected from agricultural areas in three communes—Huong Chu (HC), Phu Mau (PM), and Quang Thanh (QT)—surrounding the city (Figure 1)
The MNR representative samples collected from the compositing area during the wet season from PM and QT had E. coli counts of
Despite the low concentrations resulting from dilution, E. coli strains with links to municipal wastewater (MWW) were more widespread during the wet season

Summary

Introduction

Extreme flooding is a major cause of weather-related infectious disease outbreaks with strong links to diarrheal diseases [1,2]. The frequency and intensity of extreme precipitation events are projected to increase [1,3,4]; floods and the associated impacts will increase. Flooding overwhelms drainage systems and, in some cases, allows the mixing of waste from different sources [1,5]. Waterborne disease, and infectious diarrhea remain prominent and persistent problems worldwide, and they are expected to worsen under future climate change projections [2].

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