Influence of ethanol and nitrate on ibuprofen removal in batch reactors under denitrifying conditions

Abstract

The optimized removal of the anti-inflammatory drug ibuprofen inoculated with activated sludge biomass in batch reactors was evaluated, using the variables ibuprofen (60 – 80 µg L-1), ethanol (130 – 230 mg EtOH L-1) and nitrate (130 – 230 mg NO3- L-1) by rotational central compound design. A higher removal efficiency of ibuprofen (97.5 ± 3.1%) was observed with 95.9 mg NO3- L-1, 109.9 µg IBU L-1 and 110.6 mg EtOH L-1. Under these conditions, complete removal of NO3- (1.1 h-1 speed), 20 ± 2.7% of organic matter removal (366.5 ± 3.5 mg COD L-1)> 90% ethanol removal were obtained. Based on the mass sequencing of the 16 S rRNA gene via the Illumina platform, bacteria related to the degradation of recalcitrant compounds were identified, such as Pseudomonas (1.5%), Zoogloea (1.73%) and Rhodanobacter (1.63%). The enzymes involved in denitrification were also inferred, such as nitrate transporters and several reductases involved in the conversion of intermediates. Although ibuprofen removal occurred in the absence of ethanol (16.5%) and nitrate (15.2%), the optimal removal range (97.5%) as well as the selection of bacteria possibly involved in its degradation pathways was obtained with 110.6 mg EtOH L-1 and 95.9 mg NO3- L-1, achieving removal approximately 5.9 times higher when compared to the assays without ethanol and nitrate.