In-pipe water quality monitoring in water supply systems
under steady and unsteady state flow conditions:
A quantitative assessment
a bstra ct
Monitorin g the quality of drinking water from the treatm ent plan t to the consumers tap is
critical to ensur e compliance with nationa l standards and/orWHOguideline levels. There
are a number of processes and factor s affecting the water quality duri ng transmission and
distribution which are litt le un derstood. A sig nificant obstacle for gaining a det ailed
knowledge of variou s physica l and chemic al processe s 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 continuo us
monitoring. This paper has two object ives. The first one is to presen t a detailed evaluation
of the performa nce of a novel in-pipe mult i-parameter sensor pro be for reagent- and
membrane-f ree continuo us water quality monitoring in water supply systems. The second
objective is to describe the results from experiment al research which was conducted to
acquire continu ous water quality and high-frequency hydraulic data for the quantitative
assessment of the water quality changes occurring under stea dy and unsteady-state flow
conditions. The labora tory and field evaluation of the multi-p arameter sensor probe
showed that the sensor s have a rapid dynamic response, average repeatability and unre-liable accuracy. The uncerta inties in the sensor data presen t significant challenges for the
analysis and interpretatio n of the acquired data and their use for water quality modelling,
decision support and control in operational systems. Notwi thstanding these un certainties,
the unique data sets acqui red from transmissio n and distribution systems demonstrated
the deleter ious effect of unstea dy stat e flow conditions on variou s water quality parame-ters. These studies demonstrate: (i) the sig nificant impact of the unsteady-state hydraulic
conditions on the disinfectant res idual, turbidity and colour caused by the re-suspensio n of
sediments, scouring of biofilms and tuberc les from the pipe and increased mixing, and the
need for further experiment al res earch to investigate these interact ions; (ii) im portant
advances in sensor technologies which provide un ique opportunities to study both the
dynamic hydraulic conditio ns and water qua lity changes in operational systems. The
research in these two areas is critical to better understand and manage the water quality
deterioration in ageing water transmissio n and distribution syste ms