Automated Targeted Sampling of Waterborne Pathogens and Microbial Source Tracking Markers Using Near-Real Time Monitoring of Microbiological Water Quality

Jean-Baptiste Burnet,Zeinab Khanafer,Marc Habash,Emile Sylvestre,Pierre Servais,Sarah Dorner,Michèle Prévost,Mounia Hachad

doi:10.3390/w13152069

Abstract

Waterborne pathogens are heterogeneously distributed across various spatiotemporal scales in water resources, and representative sampling is therefore crucial for accurate risk assessment. Since regulatory monitoring of microbiological water quality is usually conducted at fixed time intervals, it can miss short-term fecal contamination episodes and underestimate underlying microbial risks. In the present paper, we developed a new automated sampling methodology based on near real-time measurement of a biochemical indicator of fecal pollution. Online monitoring of β-D-glucuronidase (GLUC) activity was used to trigger an automated sampler during fecal contamination events in a drinking water supply and at an urban beach. Significant increases in protozoan parasites, microbial source tracking markers and E. coli were measured during short-term (<24 h) fecal pollution episodes, emphasizing the intermittent nature of their occurrence in water. Synchronous triggering of the automated sampler with online GLUC activity measurements further revealed a tight association between the biochemical indicator and culturable E. coli. The proposed event sampling methodology is versatile and in addition to the two triggering modes validated here, others can be designed based on specific needs and local settings. In support to regulatory monitoring schemes, it should ultimately help gathering crucial data on waterborne pathogens more efficiently during episodic fecal pollution events.

Highlights

Acquiring meaningful data for microbial risk assessments in water is paramount and requires representative samples [1]
Rainfall has long been identified as a major trigger of waterborne outbreaks [10], as well as for the incidence of gastrointestinal illness during recreational exposure [11]
Because the direct measurement of pathogens is cumbersome and expensive, regulatory water quality monitoring mostly relies on fecal indicator bacteria (FIB) such as E. coli or enterococci (ENT), and only in a limited number of countries such as in the USA, regulatory monitoring of the protozoan pathogen Cryptosporidium is performed in source waters of large drinking water supply systems [12]

Summary

Introduction

Acquiring meaningful data for microbial risk assessments in water is paramount and requires representative samples [1]. Given the inherent variability in microbiological water quality in groundwater and surface water [2,3,4,5,6]), inadequate sampling strategies can miss intermittent contamination events [7]. Given that fecal contamination events can appear and disappear within less than 24 h at any time, even daily monitoring can miss such short-term episodes. Appropriate tools and assays are needed to enable the collection of representative data accounting for (short-term) fluctuations in microbial water quality [16], which should help improve microbial risk assessment within the framework of water safety planning [1,17]. In a recreational context, targeted assessments of the microbial risk associated with intermittent contamination events that may be missed by routine monitoring schemes would help avoid the unintended direct exposure of bathers to potential gastrointestinal-illness-causing agents

Objectives

Methods

Results