Waterboard Rijnland

Simultaneous denitrification and phosphate removal of STW effluent

Hoogheemraadschap van Rijnland is a Dutch waterboard. One of their sewage treatment works (STW) is Leiden-Noord.

To meet stricter final effluent consent levels Leiden-Noord STW is expanded with ASTRASAND® continuous filtration. A new filtration concept was implemented where nitrate and phosphate are removed in a single ASTRASAND® continuous filtration stage.

Implementation of this new filter concept was the result of 2-year full-scale trails where results of ASTRASAND® single stage filtration were similar to a two stage filter concept. In the single stage filtration concept physical filtration of precipitated phosphate and biological conversion of nitrate are combined in one filter resulting in a significant reduction of filtration surface area. A total filtration surface area of 120 m2 is installed.