Pacas Leiden

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Organic micro-contaminants and medicines in surface, ground and drinking water are receiving increasingly more administrative and public attention. Research has shown that, currently, waste water treatment plants do not remove these substances to a sufficient degree.

This is why Witteveen+Bos has devoted a lot of effort in recent years to knowledge development in this area. In 2019, we started working on designing the EU’s first full-scale PACAS installation for the Rijnland Water Authority. This is an installation for dosing powdered activated carbon (PAC) into the activated sludge system (AS) at the waste water treatment plant in Leiden.

Witteveen+Bos provided guidance to the water authority throughout the entire design process, ranging from the schedule of requirements through to implementation. Because this installation is the first of its kind in the Netherlands, we intensively collaborated with the water authority to develop an installation with maximum flexibility. The silo and the dosing system form the heart of the installation where the powdered carbon is stored and transported to the various parts of the treatment plant. The carbon is then added to the water where pharmaceutical residues combine with the carbon, after which it settles and is subsequently processed together with the sludge. In this way, Rijnland is adding an extra purification step to the existing waste water treatment process to improve the water’s quality. It is the first water authority to apply this technology.