Water temperature is often monitored at water sources and treatment works; however, there is limited monitoring of the water temperature in the drinking water distribution system (DWDS), despite a known impact on physical, chemical and microbial reactions which impact water quality. A key parameter influencing drinking water temperature is soil temperature, which is influenced by the urban heat island effects. This paper provides critique and comprehensive summary of the current knowledge, policies and challenges regarding drinking water temperature research and presents the findings from a survey of international stakeholders. Knowledge gaps as well as challenges and opportunities for monitoring and research are identified. The conclusion of the study is that temperature in the DWDS is an emerging concern in various countries regardless of the water source and treatment, climate conditions, or network characteristics such as topology, pipe material or diameter. More research is needed, especially to determine (i) the effect of higher temperatures, (ii) a legislative limit on temperature and (iii) measures to comply with this limit.

This paper proposes the modulation of nodal outflows in water distribution networks (WDNs) to solve the problem of low disinfectant concentrations at critical dead-end nodes, in which low flow velocities and long residence times cause excessive disinfectant decay. The slight increase in nodal outflows at these sites, which can be obtained through the opening of a blowoff at the hydrant site, can help to address this problem with no need to increase disinfectant doses at the source(s) or of install additional disinfectant booster stations. The methodology is based on the combined use of optimization and flow routing/water quality modeling of WDNs. The concentration of disinfectant at the source(s) and the values of nodal emitter coefficients at the critical dead-end nodes are the decisional variables to be optimized. Two objective functions are considered in the optimization: the total volume of water delivered in the network (inclusive of supply, leakage, and additional nodal outflow considered for fixing disinfectant residuals); and the total mass of disinfectant injected into the network. The effectiveness of the methodology was proven on a real WDN, yielding insight into the economic feasibility of the solution.

The present work provides a numerical comparison of different techniques that can be adopted to guarantee sufficient disinfectant residuals in a water distribution network (WDN) when chlorine or chloramine is used as disinfectant. First, while considering chlorine as a disinfectant, the implementation of booster stations in bulk areas and continuous outflows at dead-end nodes was considered. Afterward, the comparison between continuous and intermittent outflows was performed. The water volume being the same, water is provided through blowoffs for 24 h or for limited durations, respectively. Finally, the extent to which the results change was analyzed when chloramine is used instead of chlorine. The methodology is based on the use of the flow routing/water quality modeling software EPANET and its multispecies extension EPANET-MSX on a full-scale WDN. The results show that all the operational measures analyzed are effective to tackle the problem of low disinfectant residuals in WDN. Booster stations are effective to obtain a more uniform distribution of disinfectant throughout the WDN, while nodal blowoffs seem to be a necessary solution for the numerous and scattered dead-end nodes of WDN. The use of chloramine yielded a decrease in the number of blowoffs to open and in blowoff outflows.

Flushing plans within a water distribution network (WDN) provide a tool for improving disinfectant residuals and removing stagnant water. The problem of low disinfectant residuals occurs in areas of a WDN such as dead-end nodes, in which low flow conditions and long residence times lead to excessive decay of the disinfectant upstream from users. Here, a methodology is presented to maintain adequate disinfectant residuals in WDNs that have numerous dead-end nodes. The slight increase in nodal outflows at these sites, which can be obtained through the opening of a blow-off at the hydrant site, can help in tackling this problem. The methodology is based on the combined use of optimization and of flow routing/water quality modelling. The concentration of disinfectant at the source(s) and the values of nodal emitter coefficients at the critical dead-end nodes are the decisional variables to be optimized. Two objective functions are considered in the optimization, namely the total volume of water delivered in the network and the total mass of disinfectant injected into the network. The effectiveness of the methodology is proven on a real WDN, yielding an insight into the economic feasibility of the solution.