Removal of pharmaceuticals in WWTP effluents by ozone and hydrogen peroxide

Abstract

Ozonation to achieve removal of pharmaceuticals from wastewater  effluents, with pH values in the upper and lower regions of the typical  range for Swedish wastewater, was investigated. The main aim was to  study the effects of varying pH values (6.0 and 8.0), and if small additions of H₂O₂ prior to ozone treatment could improve the removal and lower the reaction time. The effluents studied differed in their chemical  characteristics, particularly in terms of alkalinity (65.3–427 mg·l^-1) HCO_3-), COD (18.2–41.8 mg·l^-1), DOC (6.9–12.5 mg·l^-1), ammonium content (0.02–3.6 mg·l^-1) and specific UV absorbance (1.78–2.76  l·mg^-1)·m^-1). As expected, lower ozone decomposition rates were  observed in the effluents at pH 6.0 compared to pH 8.0. When pH 8.0 effluents were ozonated, a higher degree of pharmaceutical removal  occurred in the effluent with low specific UV absorbance. For pH 6.0  effluents, the removal of pharmaceuticals was most efficient in the effluent with the lowest organic content. The addition of H₂O₂ had no significant effect on the quantitative removal of pharmaceuticals but enhanced the ozone decomposition rate. Thus, H₂O₂ addition increased the reaction rate. In practice, this will mean that the reactor volume needed for the ozonation of wastewater effluents can be reduced.

Keywords: ozone; pharmaceuticals; hydrogen peroxide; wastewater effluents