Seasonal variability of faecal indicator bacteria numbers and die-off rates in the Red River basin, North Viet Nam.

Huong Thi Mai Nguyen,J Garnier,J.-L Janeau,Quynh Thi Phuong Le,E Rochelle-Newall

doi:10.1038/srep21644

Abstract

The Red River is the second largest river in Viet Nam and constitutes the main water source for a large percentage of the population of North Viet Nam. Here we present the results of an annual survey of Escherichia coli (EC) and Total Coliforms (TC) in the Red River basin, North Viet Nam. The objective of this work was to obtain information on faecal indicator bacteria (FIB) numbers over an annual cycle and, secondly, to determine the die-off rates of these bacterial indicators. Monthly observations at 10 stations from July 2013–June 2014 showed that TC and EC reached as high as 39100 cfu (colony forming units) 100 ml−1 and 15300 colonies 100 ml−1, respectively. We observed a significant seasonal difference for TC (p < 0.05) with numbers being higher during the wet season. In contrast, no significant seasonal difference was found for EC. The FIB die-off rates ranged from 0.01 d−1 to a maximum of 1.13 d−1 for EC and from 0.17 d−1 to 1.33 d−1 for TC. Die-off rates were significantly higher for free bacteria than for total (free + particle attached) bacteria, suggesting that particle attachment provided a certain level of protection to FIB in this system.

Highlights

To cite this version: Huong Thi Mai Nguyen, Quynh Thi Phuong Le, J
In our work from the sub-tropical Red River system in Viet Nam, we found that faecal indicator bacteria (FIB) numbers exceed Vietnamese water quality guidelines of 20 and 150 colonies 100 ml−1 for Escherichia coli (EC) and Total Coliforms (TC), respectively, throughout the whole year at almost all of the 10 stations investigated
The use of water from sites with high FIB numbers such as those in the downstream sites pose a real risk to public health

Summary

Introduction

To cite this version: Huong Thi Mai Nguyen, Quynh Thi Phuong Le, J. Biological contamination of aquatic systems by water borne pathogens from untreated wastewater and agricultural effluent is a globally important water quality problem[1]. It is problematic in tropical regions where a large proportion of the developing world is located. Understanding the factors that control their distribution is a prerequisite for reducing the human health risks associated with the use of unclean water This is important in tropical areas where there is a paucity of data, where population growth is high, and where populations are the most exposed to these contaminants[1,3]

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Discussion

Conclusion