Investigating the biodegradation of the emerging pollutant paracetamol by bacteria communities

Neba, Donaldben Mbagag

http://hdl.handle.net/10400.1/9917

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Authors

Neba, Donaldben Mbagag

Advisor(s)

Costa, Maria Clara

Abstract(s)

Pharmaceutical active compounds are an important group of emerging pollutants that have raised an increasing interest in the scientific community due to their ubiquitous presence in the environment and their difficult degradation. Some of these drugs are extensively used as non-prescription drugs and after their intake, are excreted with urine and faeces either as active substance or metabolites. These substances come into wastewater treatment plants (WWTP) where some compounds are not efficiently removed, being able to reach surface, groundwater and subsequently, drinking water. Microorganisms (single isolates) have the potential to degrade a wide range of xenobiotics and recalcitrant contaminants. The tendency is more reinforced in their communities due to a great synergistic interaction between members of the consortium. In this study, the overall objectives aimed at investigating bacterial biodegrading communities from two different wastewater treatment plants (a passive lagoon system and an activated mud treatment system with aeration) for their abilities in effectively biodegrading and mineralizing paracetamol (APAP) and determining the optimum conditions required to achieve the outcome. The study examined the aerobic biodegradation of paracetamol by microbial communities from WWTPs in Faro using residual water and minimum salt medium (MSM) as growth media. From an obscure 25 ºC incubated aerobic aerified (110mL/min) bioreactor with paracetamol as the only carbon and energy sources, the biodegradability of paracetamol was evaluated by direct sample analysis after a 24, 48, 72 and 120hrs growth period. An elution gradient HPLC analysis for paracetamol biodegradations and the identification of its associated metabolite respectively showed a 99.9% elimination within 72hrs and a complete degradation after 120hrs for aerified samples with residual water and 97% elimination within 120hrs for aerified samples with MSM. Tentative identified peaks corresponded to the following metabolites: 4-aminophenol, hydroquinone and p-benzoquinone. The Hach-spectrophotometry analysis of the chemical oxygen demand (COD mg/L) showed a progressive decrease in the values within most batch samples hence suggesting a possible usage of the paracetamol during the process. IC50 measurements by UV-vis spectrometer produced concentration values far to be toxic for the organisms. In a nutshell, the sludge contains aerobic microorganisms capable of totally degrading APAP and the resulting metabolites to obtain energy without any other source of carbon and energy. Degradation is faster with aeration but slower without.