Selection of microbial pharmaceuticals degraders and design of a Membrane Aereated Biofilm Reactor for their exploitation in wastewater tertiary treatment

Background information: The release of non-steroidal anti-inflammatory drugs, as well as other type of pharmaceuticals, through the wastewaters system and their accumulation in the environment represent an emerging ecological problem. Microbial degradation of these compounds could be a promising strategy to be implemented within the wastewater treatment process. The MAR2PROTECT project aims to develop a combined tertiary treatment process consisting of an adsorption step, followed by a biological treatment of the concentrated eluate. Within this framework, this study aims at enriching and characterizing microbial cultures (communities and/or single strains) able to degrade ibuprofen, paracetamol, and carbamazepine in the mg/L concentration range under aerobic conditions. Parallelly, a lab-scale Membrane Aereated Biofilm Reactor (MABR) is set up for the contextual exploitation of the selected cultures to deal with a mixed contamination of pharmaceuticals. Experimental design and main results: Sludges from two municipal wastewater treatment plants (WWTP) were the source for selecting microbial degraders (strains and/or consortia), having care in selecting one WWTP that receive wastewaters from a local hospital, to increase the chance of enriching pharmaceutical degraders. Enrichment of degraders was performed by growing cultures derived from sludges in mineral medium with pharmaceuticals (ibuprofen, paracetamol, and carbamazepine, in the range of 10 mg/L to 1 g/L) as sole carbon and energy source. Biodegradation efficiency was monitored by chromatography-based quantification of the contaminant in the culture media. Ibuprofen degraders were the first and easier to select. A high-performance ibuprofen-degrading strain of Cupriavidus oxalaticus was obtained, able to completely degrade ibuprofen at a concentration of 10 mg/L in less then 6 hours. A microbial consortia of few strains able to exploit paracetamol as sole carbon source (complete degradation of 10 mg/L in less than 24 hours) was also obtained. Taxonomical characterization of this consortia is ongoing, as well as the isolation of the best performing strain. Aiming at utilizing the ibuprofen and paracetamol-degraders within the same bioreactors, tests to exclude antagonist effects among degraders have been carried out. Carbamazepine degraders have been proven more difficult to select. Promising preliminary tests indicate that a microbial consortia able to use carbamazepine as carbon source has been enriched. Parallelly to this selection activity, the lab-scale MABR reactor has been set up. Preliminary tests conducted under batch conditions using only the Cupriavidus oxalaticus strain able to degrade ibuprofen showed that the MABR is able to sustain the formation of an efficient biofilm for ibuprofen degradation. Implementation of the MABR continuous process for the treatment of ibuprofen-polluted water and its further testing with additional strains and/or consortia degrading other pharmaceuticals is ongoing, aiming at developing a process based on a multispecies biofilm with the potential to contextually degrade at least three pharmaceutical compounds.