Study of effects of pharmaceuticals on the activated sludge process combining advanced oxidation using ultraviolet/hydrogen peroxide to increase their removal and mineralization of wastewater

Abstract

Carbamazepine, acetaminophen, diclofenac, sulfamethoxazole and 17-α- ethinylestradiol have been identified as pharmaceuticals of high ecotoxic risk and widespread presence in wastewaters. Recent studies suggest some pharmaceuticals can affect activated sludge (AS) biomass in terms of microbial community profile, however without focusing on the macroscopic aspects of the process. So this work evaluates the effect of introducing these five pharmaceuticals at μg.L-1 concentration in synthetic municipal wastewater, measuring response both in macroscopic (quality parameters of biologically treated effluent and biomass’ oxygen uptake rate) and microscopic (genera and phyla) aspects. As these pharmaceuticals are not completely removed by AS, a subsequent increase in their removal and mineralization of recalcitrant organics was sought by applying an oxidation process with UV/ H2O2. There was an increase of 3.4 times in true color, 7.7 times in turbidity, 2.2 times in Chemical Oxygen Demand (COD) and a decrease of 48 % in oxygen uptake rate (OUR) immediately after the insertion of the pharmaceuticals, but all parameters returned to original values after 22 days of acclimatization, indicating that biomass microbial community modified to adapt to the introduction of the pharmaceuticals. Identification of microbial species showed changes in the proportion of bacterial genera and phyla. A 10 mg/L dose of H2O2 with UV after biological treatment reached log reductions between 1.80–2.43 for the pharmaceuticals. However, to obtain removal of organics higher than 30 %, H2O2 doses greater than 30 mg/L were necessary. Mineralization of biologically treated effluent was obtained with UV dose 130.5 kJ/m² and H2O2 dose 200 mg/L.