Towards tertiary micropollutants removal, by bio-augmented moving bed biofilm reactors and nanofiltration

Image result for mehran utwente abtahi foroushaniIn this thesis, reducing the release of emerging micropollutants (MPs) into the surface water, is the center of focus. ‘The potential risk of MPs, constantly discharged from municipal wastewater treatment plants, is now under active evaluation among researchers worldwide.,’ Seyed Mehran Abtahi Foroushani says.

To broaden such knowledge, two advanced treatments were studied: bioaugmented moving bed biofilm reactors (MBBRs) and polyelectrolyte multilayer (PEM)-based nanofiltration (NF) membranes. The main aim was to elucidate their potential for the elimination of several MPs (Diclofenac, Naproxen, 4n-Nonylphenol, 17ß-Estradiol, and Ibuprofen) from conventionally-treated municipal wastewater.

Three identical lab-scale MBBRs, each with an effective volume of 3.1 litre, were operated in the continuous mode of operation . ‘Individual contributions of the biofilm and suspended biomass in MPs removal were determined,’ Mehran says. ‘Subsequently, we could obtain abiotic and biotic removal of MPs along with their dominant biodegradation mechanisms.’

Sorption of MPs onto the suspended biomass was seen around two times more than the biofilm, while the biofilm was more powerful in the elimination of all MPs. ‘When comparing abiotic and biotic aspects, biotic removal outperformed its counterpart for all tested pollutants,’ Mehran concludes.

Meanwhile, two out of three MBBRs were inoculated by pseudomonas-fluorescens, with a novel protocol, and operated under identical conditions, with the non-bioaugmented (control)   MBBR. Bioaugmented MBBRs showed a high potential for the elimination of target MPs (in particular Diclofenac). ‘However, this technology still needs further detailed research, to overcome existing challenges,’ Mehran says. ‘I hope future researchers will take on this approach and bring applications closer to today’s market.’

Mehran is even the more enthusiastic about the second direction of research within his PhD project: MPs removal by Polyelectrolyte multilayer (PEM)-based nanofiltration (NF) membranes.

PEMs are prepared by alternately adsorbing the oppositely-charged polyelectrolytes onto the supports, using a layer by layer (LbL) technique. ‘PEMs of two weak polyelectrolytes were used: poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA),’ Mehran says. ‘Two types of ultrafiltration (UF) supports (hollow fiber silica (HFS) and flat-sheet polyacrylonitrile (PAN) membranes) were used for the surface modification.’

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