River-bank filtration as alternative to direct intake

Surface water utilities in the Netherlands frequently intake their river water directly, or after the water is first stored in a reserve or reservoir. One of the first steps in the treatment process involves the use of microscreening, followed by coagulation and filtration. Substituting the direct intake by river-bank filtration perhaps offers an attractive alternative option at some sites. This project will use a desk study to inventory the available possibilities.

Advantages of river-bank filtration

One drawback of the typical direct intake process is that there is no levelling of the concentrations of substances, such as organic micropollutants and chloride, before the water is pre-treated or placed in the reservoir. The same applies to the temperature of the river water. Moreover, algal growth can occur in a reservoir, which adds to the load on the subsequent treatment processes.

Implementation of river-bank filtration perhaps offers solutions to these problems. Pre-treatment with microscreening and coagulation (removal of suspended solids) may become unnecessary. A levelling occurs in the water quality – for example, regarding salinity, organic micropollutants and temperature. This might make it possible to avoid intake suspensions.

There is also the chance that river-bank filtration will reduce possible algal growth problems and lead to the degradation of organic micropollutants. Moreover river-bank filtration could also have a positive effect on the biological stability.

The drawback of river-bank filtration is that the water can become anoxic, possibly resulting in increased concentrations of total P, iron and arsenic. Since river-bank filtration requires fewer chemicals and energy consumption is reduced, it implies a more efficient and stable treatment process. This means that its installation costs in existing areas could possibly be recovered.

Literature study and elaboration of a scenario study

We will begin this project with a literature study to examine the current experience with river-bank filtration. Factors such as the impact of residence time, the difference between lake-bank and river-bank filtration, and the effect on biological stability will be considered. During a subsequent working session with the participating water utilities, one scenario will be selected for further elaboration. We will examine a variety of aspects, such as: adaptation to the site, consequences for water quality, distinction in light oxic or anaerobic abstraction, consequences for the production, impact on nature in the reservoirs, ecological potentials, impact of the residence time and options for simplification of the treatment.

Application possibilities for water utilities

This research will provide water utilities with insight into the possibilities offered by river-bank filtration to lighten the treatment effort, improve water quality, improve ecology and possibly reduce costs.