History

The Houtrust wastewater treatment plant was built in 1967 in response to booming economic and industrial growth in the region of The Hague. The treatment plant was equipped for chemical/physical wastewater treatment. Later in 1988, the plant was upgraded with a biological treatment unit. A sludge dewatering treatment unit was added in 1990. Chemical phosphorus removal occurs since 1995.

In 1999, the Delfland Water Board launched an international request for proposals to improve its treatment capacity in order to comply with new European environment regulations. The contract was awarded to the Delfluent consortium of five companies: Veolia Water (40%), Evides (40%), Rabobank (10 %), Heijmans (5%) and Strukton (5%).