Potential impacts of changing supply-water quality on drinking water distribution: A review

Abstract

Driven by the development of water purification technologies and water quality regulations, the use of better source water and/or upgraded water treatment processes to improve drinking water quality have become common practices worldwide. However, even though these elements lead to improved water quality, the water quality may be impacted during its distribution through piped networks due to the processes such as pipe material release, biofilm formation and detachment, accumulation and resuspension of loose deposits. Irregular changes in supply-water quality may cause physiochemical and microbiological de-stabilization of pipe material, biofilms and loose deposits in the distribution system that have been established over decades and may harbor components that cause health or esthetical issues (brown water). Even though it is clearly relevant to customers' health (e.g., recent Flint water crisis), until now, switching of supply-water quality is done without any systematic evaluation. This article reviews the contaminants that develop in the water distribution system and their characteristics, as well as the possible transition effects during the switching of treated water quality by destabilization and the release of pipe material and contaminants into the water and the subsequent risks. At the end of this article, a framework is proposed for the evaluation of potential transition effects.

Long-term spatial and temporal microbial community dynamics in a large-scale drinking water distribution system with multiple disinfectant regimes

“…Microbial growth in drinking water has been observed in the form of higher particle counts and increased turbidity (Liu et al, 2016), higher cell counts (Hammes et al, 2008) and increase in the presence of indicator organisms in the final tap water compared to the water leaving the treatment plant (van der Wielen et al, 2016). The water leaving the treatment plant may therefore be impacted by the distribution system itself through processes such as pipe corrosion (Sun et al, 2014), the detachment of biofilms (Chaves Simões and Simões, 2013) and suspension of loose deposits (Liu et al, 2013;Liu et al, 2017;Liu et al, 2018). These processes together in combination with increasing contact time with the disinfectant may explain the observed spatial dissimilarity observed in the bacterial community as bulk water moves away from the DWDP and through the DWDS.…”

“…These systems are complex aquatic environments with multiple ecological niches that support microbial growth through the different stages of the DWDS. The microbial ecology of DWDSs is governed by environmental and engineering factors as well as operational conditions that influence the composition and structure of bacterial communities present in the biofilms, bulk water and sediments (Liu et al, 2013;Prest et al, 2016a;Liu et al, 2017). Despite disinfection during water treatment, microorganisms grow during distribution with reported microbial cell numbers ranging between 10 4 -10 6 cells per litre (Hammes et al, 2008).…”

The impact of rainfall on drinking water quality in Antananarivo, Madagascar

“…Among these factors, the effectiveness of the treatment process is certainly the most important and must be carefully adapted to the quality of the incoming raw water. However, hydraulic conditions (e.g., flow velocity and intermittent water supply) and water quality (e.g., presence of sediments or excess of turbidity) can enhance bacterial growth and sediment dissolution in final drinking water [17,42].…”

Provenance of drinking water revealed through compliance sampling

“…11 In this case, the addition of highly corrosive surface water into a distribution system without corrosion control resulted in a signicant public health incident. 12 Outside of the UK switching of supply water chemistry may be done without any systematic evaluation, 13 and assessing the impacts of drinking water chemistry on potential future large scale raw and potable transfers is considered a signicant research need. 14 The hydrochemical analyses required in order to support assessment of the water quality implications of transfers are complex.…”