Effluent treatment by multi-media filtration, microfiltration and ultrafiltration: results of a pilot investigation at WWTP Hoek van Holland.

Upgrading of wastewater treatment plant (WWTP) effluent as a part of the Dutch governmental policy to close the water cycle has increasing interest now. The Water Board Hoogheemraadschap van Delfland together with the project team of Witteveen + Bos Consulting Engineers, Delft University of Technology and Rossmark water treatment investigated the reuse possibilities of WWTP effluent in the region of Delfland. Therefore pilot research was carried out at WWTP Hoek van Holland applying different filtration techniques: multi-media filtration, micro- and ultrafiltration. The results show stable process performances of the different filtration techniques when proper pre-treatment was applied. For microfiltration the filtration characteristics were strongly influenced by particles which were not retained in the multi-media filter. For ultrafiltration the filtration characteristics were strongly influenced by organic components < 0.2 microm. The upgraded WWTP effluent could not be used directly as process water or for agriculture purposes, due to high concentrations of COD and salts in the WWTP effluent and filtrates. However WWTP effluent or floc filtrate could be applied directly as water for the washing of sea-sand.