Biological removal processes in aerobic granular sludge exposed to diclofenac

ABSTRACT

Diclofenac is a worldwide consumed drug included in the watch list of substances to be monitored according to the European Union Water Framework Directive (Directive 2013/39/EU). Aerobic granular sludge sequencing batch reactors (AGS-SBR) are increasingly used for wastewater treatment but there is scant information on the fate and effect of micropollutants to nutrient removal processes. An AGS-SBR fed with synthetic wastewater containing diclofenac was bioaugmented with a diclofenac degrading bacterial strain and performance and microbial community dynamics was analysed. Chemical oxygen demand, phosphate and ammonia removal were not affected by the micropollutant at 0.03 mM (9.54 mg L^–1). The AGS was able to retain the degrading strain, which was detected in the sludge throughout after augmentation. Nevertheless, besides some adsorption to the biomass, diclofenac was not degraded by the augmented sludge given the short operating cycles and even if batch degradation assays confirmed that the bioaugmented AGS was able to biodegrade the compound. The exposure to the pharmaceutical affected the microbial community of the sludge, separating the two first phases of reactor operation (acclimatization and granulation) from subsequent phases. The AGS was able to keep the bioaugmented strain and to maintain the main functions of nutrient removal even through the long exposure to the pharmaceutical, but combined strategies are needed to reduce the spread of micropollutants in the environment.

GRAPHICAL ABSTRACT

KEYWORDS:

• Diclofenac
• Labrys portucalensis F11
• aerobic granular sludge sequencing batch reactor
• bioaugmentation
• performance

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

V.S. Bessa wish to acknowledge research grant from Fundação para a Ciência e Tecnologia (FCT), Portugal [Ref. SFRH/BD/90146/2012] and Fundo Social Europeu (Programa Operacional Potencial Humano (POPH), Quadro de Referência Estratégico Nacional (QREN)). This work was supported by National Funds from FCT – Fundação para a Ciência e a Tecnologia – through the project AGeNT – PTDC/BTA-BTA/ 31264/2017 [POCI-01-0145-FEDER-031264]. We would also like to thank the scientific collaboration of CBQF under the FCT project UIDB/50016/2020.