In-pipe water quality monitoring in water supply systems
under steady and unsteady state ow conditions:
A quantitative assessment
Monitoring the quality of drinking water from the treatment plan t to the consumers tap is
critical to ensure compliance with national standards and/or WHO guideline levels. There
are a number of processes and factors affecting the water quality during transmission and
distribution which are little understood. A signi cant obstacle for gaining a detailed
knowledge of various physical and chemical processes and the effect of the hydraulic
conditions on the water quality deterioration within water supply systems is the lack of
reliable and low-cost (both capital and O & M) water quality sensors for continuous
monitoring. This paper has two objectives. The rst one is to present a detailed evaluation
of the performance of a novel in-pipe multi-parameter sensor probe for reagent- and
membrane-free continuous water quality monitoring in water supply systems. The second
objective is to describe the results from experimental research which was conducted to
acquire continuous water quality and high-frequency hydraulic data for the quantitative
assessment of the water quality changes occurring under steady and unsteady-state ow
conditions. The laboratory and eld evaluation of the multi-parameter sensor probe
showed that the sensors have a rapid dynamic response, average repeatability and unre-
liable accuracy. The uncertainties in the sensor data present signi cant challenges for the
analysis and interpretation of the acquired data and their use for water quality modelling,
decision support and control in operational systems. Notwithstanding these uncertainties,
the unique data sets acquired from transmission and distribution systems demonstrated
the deleterious effect of unsteady state ow conditions on various water quality parame-
ters. These studies demonstrate: (i) the signi cant impact of the unsteady-state hydraulic
conditions on the disinfectant residual, turbidity and colour caused by the re-suspension of
sediments, scouring of bio lms and tubercles from the pipe and increased mixing, and the
need for further experimental research to investigate these interactions; (ii) important
advances in sensor technologies which provide unique opportunities to study both the
dynamic hydraulic conditions and water quality changes in operational systems. The research in these two areas is critical to better understand and manage the water quality
deterioration in ageing water transmission and distribution systems