Suitability of Optical, Physical and Chemical Measurements for Detection of Changes in Bacterial Drinking Water Quality

Jenni Ikonen,Ilkka Miettinen,Tarja Pitkänen

doi:10.3390/ijerph10115349

Abstract

In this study, different optical, physical and chemical measurements were tested for their capacity to detect changes in water quality. The tests included UV-absorbance at 254 nm, absorbance at 420 nm, turbidity, particle counting, temperature, pH, electric conductivity (EC), free chlorine concentration and ATP concentration measurements. Special emphasis was given to investigating the potential for measurement tools to detect changes in bacterial concentrations in drinking water. Bacterial colony counts (CFU) and total bacterial cell counts (TBC) were used as reference methods for assessing the bacterial water quality. The study consists of a series of laboratory scale experiments: monitoring of regrowth of Pseudomonas fluorescens, estimation of the detection limits for optical measurements using Escherichia coli dilutions, verification of the relationships by analysing grab water samples from various distribution systems and utilisation of the measurements in the case of an accidentally contaminated distribution network. We found significant correlations between the tested measurements and the bacterial water quality. As the bacterial contamination of water often co-occurs with the intrusion of matrixes containing mainly non-bacterial components, the tested measurement tools can be considered to have the potential to rapidly detect any major changes in drinking water quality.

Highlights

Prevention and control of unfavourable changes in drinking water quality are daily challenges in waterworks worldwide
When we studied the detection limits of the optical measurements (UV-absorbance, turbidity and particle counts; Figure 2) using E. coli dilutions in spring water, it was concluded that bacterial concentrations higher than 106 CFU/mL can be measured reliably with the used equipment
Our results indicated that absorbance measurements (254 nm, 420 nm) have potential to work at some extend as tools that could be used for detecting bacterial regrowth and intrusions in drinking water systems

Summary

Introduction

Prevention and control of unfavourable changes in drinking water quality are daily challenges in waterworks worldwide. The origin of raw water, water treatment techniques, and bacterial regrowth (biofilm formation) in distribution systems influences water quality and distribution systems can be considered as biological and chemical reactors that interact with transported water [1,2,3]. Efficient removal of nutrients is required to prevent bacterial regrowth in distribution systems. The monitoring of drinking water quality focuses on verification of the water quality in the distribution system [9]. Continuous monitoring of water quality in distribution systems is rare in routine water quality verification procedures and transient deterioration of water quality in the system might not been detected

Methods

Discussion

Conclusion