Bacteriology of drinking water distribution systems: an integral and multidimensional review

Abstract

A drinking water distribution system (DWDS) is the final and essential step to supply safe and high-quality drinking water to customers. Biological processes, such as biofilm formation and detachment, microbial growth in bulk water, and the formation of loose deposits, may occur. These processes will lead to deterioration of the water quality during distribution. In extreme conditions, pathogens and opportunistic pathogens may proliferate and pose a health risk to consumers. It is, therefore, necessary to understand the bacteriology of DWDSs to develop effective strategies that can ensure the water quality at consumers' taps. The bacteriology of DWDSs, both the quantitative growth and the qualitative bacterial community, has attracted considerable research attention. However, the researchers have focused mainly on the pipe wall biofilm. In this review, DWDS bacteriology has been reviewed multidimensionally, including both the bacterial quantification and identification. For the first time, the available literature was reviewed with an emphasis on the subdivision of DWDS into four phases: bulk water, suspended solids, loose deposits, and pipe wall biofilm. Special concentration has been given to potential contribution of particulate matter: suspended particles and loose deposits. Two highlighted questions were reviewed and discussed: (1) where does most of the growth occur? And (2) what is the contribution of particle-associated bacteria to DWDS bacteriology and ecology? At the end of this review, recommendations were given based on the conclusion of this review to better understand the integral DWDS bacteriology.

Assessing biofilm development in drinking water distribution systems by Machine Learning methods

“…Different fluorescent dyes can be used. Some of the most commonly used dyes to quantify microorganisms in biofilm and water samples are acridine orange (AO) [125], 4,6-di-amino-2 phenylindole (DAPI) [126] and 5-cyano-2,3 Dytolyl Tetrazolium Chloride (CTC) [127].The reported TCC results are 10 5 to 10 7 cells/ml in bulk water, 10 5 to 10 7 cells/cm 2 on pipe wall biofilm [128].…”

“…It can count both the cultivable and non-cultivable cells with high sensitivity and accuracy [128]. Direct count and flow cytometry methods have been compared…”

“…However, the use of FCM in the field of drinking water distribution system research is an emerging technique [128]. There are, to date, few FCM results of pipe wall biofilm bacteria available.…”

“…It is a rapid approach with low detection limits [128]. Adenosine triphosphate (ATP) is the major form of cellular energy.…”

“…The use of ATP is well-established in drinking waterrelated research and is used as a reliable method to estimate microbial activity [111]. ATP has been successfully used to quantify active biomass in water treatment processes, distributed water, and pipe wall biofilm bacteria in drinking water distribution systems [128]. However, it must be noted that ATP measurement gives no indication of activity in situ [7].…”