Fieldcase WPC De Blankaart by De Watergroep and VITOThe Belgian drinking water utility De Watergroep tested together with research institute VITO - P filtration systems in their drinking water production center De Blankaart where surface water is being treated to high drinking water standards. Since some years De Watergroep has to cope increasingly with the consequences of eutrophication caused by nutrient input from the surrounding area.
This field test was located near the drinking water reservoir and production site De Blankaart (Diksmuide, Belgium).
A self-designed flexible pilot installation was built consisting of three down-flow columns (diameter 40 cm, height 150 cm), which can be either operated in a parallel or serial mode (Figure 2 and Figure 3). The flow is controlled by adapting the height of the water level in the column above the filter materials and can vary between 50 and 1000 L hour-1. Online measurements of flow rate, pressure, pH and NTU were performed for continuous monitoring.
This test was taken in operation in april 2018. As filter medium the VITO sorbent A was used: a granulated sorbent, produced by VITO from Aluminum sludge, which is a by-product from our own drinking water treatment process.
Three filters in parallel were built, of which one has been in operation for over a year now. The others will be filled with other material types, for comparative tests, this spring. Online measurements of flow rate, pressure, pH and NTU were performed for continuous monitoring. Samples of the raw water going to the filter as well as samples of the filter outlet (taken automatically on a daily basis) were analyzed in the lab for phosphorous concentration.
In the first 6 months of the trial the focus was on strength and durability of the filter material and its sensitivity to clogging. In this period, coinciding with spring and summer, the presence of algae led to the installation of an extra pre-filter and the optimization of the back-washing regime for the filter columns.
In the fall of 2018 the saturated filter material was sent back to VITO for regeneration experiments, and the filter column was restarted with fresh filter material.
The phosphorous removal efficiency was found between 30 and 60 % during the months thereafter. However, as water temperatures dropped during winter, the removal was less performant or even non-existent. The contact time of 10 to 15 minutes, for which the filter columns were designed is probably too low for P removal at water temperatures below 6°C.
In the next phase of the experiment, three different filter materials will be tested in parallel for their phosphorous removal capacity. In addition, a new filter setup will be designed and built to increase contact times in order to cope with low water temperature next winter.