Transformation of diclofenac in hybrid biofilm–activated sludge processes

Abstract

The biotransformation of diclofenac during wastewater treatment was investigated. Attached growth biomass from a carrier-filled compartment of a hybrid-MBBR at the wastewater treatment plant (WWTP) in Bad Ragaz, Switzerland was used to test the biotransformation. Laboratory-scale incubation experiments were performed with diclofenac and carriers and high-resolution LC–QTof-MS was implemented to monitor the biotransformation. Up to 20 diclofenac transformation products (TPs) were detected. Tentative structures were proposed for 16 of the TPs after characterization by MS2 fragmentation and/or inferring the structure from the transformation pathway and the molecular formula given by the high resolution ionic mass. The remaining four TPs were unambiguously identified via analytical reference standards. The postulated reactions forming the TPs were: hydroxylation, decarboxylation, oxidation, amide formation, ring-opening and reductive dechlorination. Incubation experiments of individual TPs, those which were available as reference standards, provided a deeper look into the transformation pathways. It was found that the transformation consists of four main pathways but no pathway accounted for a clear majority of the transformation. A 10-day monitoring campaign of the full-scale plant confirmed an 88% removal of diclofenac (from approximately 1.6 μg/L in WWTP influent) and the formation of TPs as found in the laboratory was observed. One of the TPs, N-(2,6-dichlorophenyl)-2-indolinone detected at concentrations of around 0.25 μg/L in WWTP effluent, accounting for 16% of the influent diclofenac concentration. The biotransformation of carriers was compared to a second WWTP not utilising carriers. It was found that in contact with activated sludge, similar hydroxylation and decarboxylation reactions occurred but at much slower rates, whereas some reactions, e.g. reductive dechlorination, were not detected at all. Finally, incubation experiments were performed with attached growth biomass from a third WWTP with a similar process configuration to Bad Ragaz WWTP. A similarly effective removal of diclofenac was found with a similar presence of TPs.

Effects of Low Concentration of Selected Analgesics and Successive Bioaugmentation of the Activated Sludge on Its Activity and Metabolic Diversity

“…The sensitivity of microorganisms to this compound could be partly responsible for the harmful effects of DCF and/or DCF-containing mixtures on the microbial biodiversity in the AS. Jewell et al [56] revealed 88% removal of the initial concentration of DCF (1.6 µg L −1 ) in the influent of the full-scale WWTP during 10-day monitoring experiment and confirmed the formation of several by-products. In this study, significant differences in DCF removal were found between the bioaugmented assay AS1 and non-bioaugmented AS2.…”

“…The accumulation of O-desmethylnaproxen, a key by-product of NPX degradation, identified e.g., for B. thuringiensis B1(2015b) [58], was excluded by the UHPLC MS/MS analysis. For DCF, 4-OH-DCF and lactam DCF are known as one of the most important initially formed secondary metabolites during microbial degradation [56]. The constant presence of 4-OH-DCF was confirmed in the AS1 assay using the UHPLC MS/MS with the highest value at t 21 .…”

A fugacity model assessment of ibuprofen, diclofenac, carbamazepine, and their transformation product concentrations in an aquatic environment

“…However, CBZ apparently biodegrades only in soils (Radke and Maier 2014 ; Li et al 2013 ). As the number of possible TPs is high for each IBU (Ferrando-Climent et al 2012 ; Vione et al 2011 ), DCF (Jewell et al 2016 ; Agüera et al 2005 ), and CBZ (Kosjek et al 2009 ), a subset of them was selected for inspection. The parent compounds, the selected TPs, and their relevant properties are listed in Tables 1 , 2 , and 3 .…”

Dissipation of Micropollutants in a Rewetted Fen Peatland: A Field Study Using Treated Wastewater

“…Due to the negative charge, sorption to the negatively loaded humic substances of the peat seems to be insignificant. The biotransformation of diclofenac is described as small [10], but mostly under oxic conditions [10,41]. Photodegradation, as a dominant process for the removal [42], is dependent on the pattern of soil cover by Phragmites australis which provides shadow on a brown soil surface.…”