Biodegradation of diclofenac and ibuprofen in Fluidized Bed Reactor applied to sanitary sewage treatment in acidogenic and denitrifying conditions

Abstract

The diclofenac (DCF) and ibuprofen (IBU) removal were assessed in an enlarged scale denitrifying Fluidized Bed Reactor (FBR), fed with sanitary sewage plus ethanol (74–100 mg L−1) and nitrate (89–136 mg L−1). The experiment was sectioned into four phases. In Phase I the Hydraulic Retention Time (HRT) was set in 18 ± 3 h without DCF and IBU addition and the FBR shows a heterotrophic denitrifying behavior with 97 % nitrate removal. In Phase II the addition of pharmaceuticals did not change COD and nitrate removal. In Phase III the HRT was decreased to 12 ± 1 h which did not influence denitrification but decreased the efficiency of DCF (35 %) and IBU (40 %) removal. In Phases I, II and III the removal of organic matter was limited by the concentration of influent nitrate. The HRT was then increased in Phase IV to 18 ± 2 h and nitrate was not added to the feeding; which led to denitrification no longer being the preferential route and replaced by acidogenic metabolism, evidenced by the highest concentration and diversity of total volatile fatty acids (VFA), resulting in increased organic matter removal efficiency (56 %), DCF (53 %), IBU (56 %) and ethanol (99.7 %). In Phase IV, acidogenic bacteria were mainly responsible for DCF and IBU degradation by ω and β-oxidation. This study establishes that DCF and IBU biodegradation in FBR applied to sanitary sewage treatment in denitrifying condition is overcome by acidogenic metabolism in the absence of nitrate as an electron acceptor, favoring the pharmaceuticals degradation.