Abstract
Water quality failures caused by discolouration has become a serious problem for water service providers as they seek measures to comply with increasingly stringent standards from regulatory authorities. Such measures include tools that would enable them predict discolouration events before they occur, so that they can act in a more proactive manner. This paper demonstrates how high temporal monitoring of the distribution networks could be a useful tool for better prediction and management of discolouration. The turbidity results from high temporal measurements show that the bulk of sediment movement across networks are at low concentration; 75% of sediment movement caused by hydraulic disturbance was of low quantity (< 2 NTU), why 13% was of higher quantity (> 4 NTU). This suggests that during normal operations, distribution networks are in most cases, self-cleaning. Monitoring of sediment movement at low concentration proved to be useful in predicting discolouration risks as an increase of the former by 37 to 50% resulted in a quality failure in most cases. Such observation of sediment movement in a network was possible with measurements at high temporal resolution. High temporal resolution data was also used to map sediment budget of 0.032 kg in a section of a 400 m length network, which was equivalent to 1.04 gm-1y-1. It was also possible to monitor turbidity with residual chlorine concentration which gave a weak positive r2 value of 0.107. Overall, the results suggest that a great deal of water quality information could come from high resolution monitoring of networks and therefore could help to proactively reducing discolouration risk.
Key words: Water quality, turbidity, sediment movement, discolouration, hydraulic disturbance.
