Water Quality Audit in Drinking Water Distribution Networks

Water and energy audits in water distribution networks have been developed to assess water losses and energy losses, respectively. However, no study has considered a water quality audit. This study proposes a concept of free residual chlorine (FRC) mass audit to quantify FRC losses as a tool for water quality management. The components defined in the FRC mass balance are analogous to the components in the International Water Association water balance. The FRC mass balance metric can show (1) the loss of FRC mass through water losses, (2) the decay of FRC by chemical reactions, and (3) the amount of FRC that reaches customers. Applying this concept to a real network, it is found that the percentage of FRC mass losses is higher than the percentage of water losses due to decay by reactions. Three performance indicators are proposed to assess the FRC losses, safety, and reliability of water distribution systems in terms of water quality.