Removal of micropollutants from water by ozonation/biofiltration process

In the paper results of studies on phenol removal by the combination of processes: ozonation and subsequent biofiltration are presented. Phenol model solution of concentration 10 mg/dm3 was applied in the experiments. During oxidation process ozone doses in range of 0.7-2.5 mg O3/mg TOC were applied and contact time varied from 1 to 5 min. WG 12 granular activated carbon (Gryfskand, Poland) was used as a filter medium. Biological activity of carbon filter was obtained by circulation of surface water through the filter. During the ozonation/biofiltration studies biomass activity changed from 126 nmol PO4 per g media to 86 nmol PO4 per g media at the top of the filter whereas biomass activity at the bottom of filter was by 12-15% lower. In the biofiltration experiments empty bed contact time (EBCT) of the filter varied from 2.4 min to 24.0 min. The applied ozone doses and contact times of oxidant with treated water were not sufficient enough in phenol removal whereas the combination of ozonation and biofiltration processes was found to be effective to remove phenol significantly (91-100% removal effect). Chemical oxygen demand removal ranged from 58 to 93% whereas biochemical oxygen demand removal was in range of 49-85%. Total organic carbon was removed from the model solution in 38-74% depending on applied process parameters.