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UNESCO-IHE Institute for Water Education, Delft (2018)

Effects of operational strategies on drinking water quality in intermittent water supply systems : the case of Moamba, Mozambique

Quaye, Michael Nii Aryee

Titre : Effects of operational strategies on drinking water quality in intermittent water supply systems : the case of Moamba, Mozambique

Auteur : Quaye, Michael Nii Aryee

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2018

Résumé partiel
The prevalence of intermittent water supply (IWS) is a global challenge, and IWS has been often associated with poor drinking water quality. The mechanisms which contribute to water quality deterioration and the perceptions of consumers under intermittent supply have been studied in recent years, but there are still unknowns both in terms of fundamental research and applied research. Regarding the latter, water operators still need to fully understand how operation of IWS systems can affect water quality, and consequently develop strategies for improving water quality within the distribution system until reaching the consumers’ taps. This study is aimed at assessing and improving operational strategies in an IWS system of a small town of southern Mozambique. In this context, different chlorine dosages and chlorine dosing strategies were tested to understand their effect on water quality. Moreover, the effect of first flush and duration of supply were investigated. Water quality was monitored in different points along one line in the distribution from the outlet of the water tower, through 4 consumers’ taps up to a distance of 2.2 km from the water treatment plant. Under the different operational strategies, physico-chemical parameters (free and total chlorine, turbidity, pH, conductivity and temperature) and faecal indicators (E.coli and total coliforms) were monitored. In the baseline assessment, 10 out of 34 samples from the taps had free residual chlorine concentration lower than 0.2 mg/L and none of the 34 samples had a residual chlorine concentration greater than 0.4 mg/L. 68% of the collected samples from both neighbourhoods revealed to have the presence of indicator bacteria. The mean value of E.coli present was 2 CFU/100mL. An average free residual chlorine of 0.46 mg/L was observed during the chlorine dosage and dosing strategy optimization experiment and this resulted in a reduction in the number of samples positive to faecal contamination in the distribution system.

Sujets  : drinking water water supply systems Mozambique water quality

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Page publiée le 1er avril 2021