Purification in water reservoirs

Keeping water quality high by effectively anticipating future developments

Water reservoirs fulfil several functions in the provision of drinking water. To begin with, a reservoir improves the quality of the water [natural purification through sedimentation of particles, photolysis and substance degradation, chemical water treatment (such as softening), but also the levelling of peaks (substance concentration, temperature)]. And reservoirs also have a storage/buffer function. The reservoir thus determines to a large degree the quality of the raw water that flows to the treatment plant. PWN has two (small) reservoirs at the IJsselmeer lake which supply the raw water to two sites: WPJ (Prince Juliana water production station) and PSA (Andijk pump station).

Developments within and outside of the drinking water sector can have an impact on water quality in the reservoirs (for example, reuse of residual streams, installation of solar panels, aquifer thermal energy storage systems and climate change). We currently do not have an adequate understanding of the internal and external parameters that influence the water quality in the PWN reservoirs. Better insight into the factors influencing reservoir water quality would allow us to optimise reservoir management. We would therefore be able to anticipate future developments and keep the water quality in these reservoirs high.

The objective of this research is to acquire better insight into the operation of the PWN reservoirs, and of the internal and external parameters that influence the water quality, with a view to effectively anticipating future developments in the reservoirs and to keeping water quality high.

Description and analysis lead to recommendations

The project includes a systematic description of the design and operational management of the two PWN reservoirs. This encompasses aspects like water quality [chemical, (micro)biological, aesthetic (taste/odour)], purification effects, chemical water treatment, stratification, intake policy, organisation/management, nature values and monitoring. It will also include an analysis of the historical water-quality data and a numerical estimate of the purification effect of the reservoirs.

The project will describe an ideal reservoir (based partly on the literature), examine which water-quality parameters provide the most information, and make recommendations for an extra sampling programme.

In addition, the current problems at the PWN and Evides reservoirs will be identified, as will the problems to be expected in the future as a consequence of climate change, salinisation, greater diversity and concentration of emerging substances, and future plans for the IJsselmeer lake (inasmuch as they’re known).

The project will then identify which parameters are needed in the reservoir management and what their effect is on water quality.

The results of the research, control parameters and future adjustments and scenarios will be discussed in a workshop with water sector experts. All of this material will be included in a BTO report.

Determining parameters and effects

At the conclusion of this project, more insight will have been acquired on the parameters that influence the water quality in the water reservoir system. In addition, the possible impact of future adjustments and climate change on the water quality in the reservoirs will have been identified.

The project’s anticipated outcomes are: a system description of the current reservoirs and a description of an ideal reservoir, based on a literature study and the experience of experts; a determination of control parameters and an estimate of their effect on water quality; an estimate of the effect of future modifications to the reservoirs; and an estimate of the impact of climate change.