Removal of humic acids by the ozonation–biofiltration process

Abstract

A study on ozonation and biofiltration of model humic acid (HA) solutions was performed. The model solutions of commercial HA (concentration of approx. 8 mg l -1) both oznated and non-ozonated were filtrated through biologically activated carbons (BAC). In the ozonation process an ozone dose of 1.4 mg per mg of total organic carbon (TOC) and a 1-min contact time were applied. Biological activity of the GAC filters were obtained by circulation of river water through the filters over periods of 3 months (WG-12 and AG-5 carbons, designated as WG-3M and AG-3M, respectively) or 23 months (WG-12 carbon designated as WG-23M). Four empty bed contact times in range of 2.3– 23.1 min were applied in the biofiltration experiments. The amount of biomass was measured as an indicator of biological activity of the granular carbon. For this purpose, a phospholipid extraction method was used. During the experiment the WG-23M filter had the highest biomass (in a range of 28–81 nmol PO 4 g -1) while biomass on the AG-3M was the lowest (ranging from 6 to 32 nmol PO 4 g -1). The effectiveness of the HA solution purification was measured by the following parameters: TOC, UV 254 absorbance, chemical oxygen demand and color. The results showed that ozonation improved the extent of the model solution purification. The most efficient in purification of both ozonated and non-ozonated HA solution was the BAC designated as AG-3M, whereas WG-23M was the least efficient in removing HA from water.