Investigating the fate of iodinated X-ray contrast media iohexol and diatrizoate during microbial degradation in an MBBR system treating urban wastewater

Abstract

The capability of a moving bed biofilm reactor (MBBR) to remove the iodinated contrast media (ICM) iohexol (IOX) and diatrizoate (DTZ) from municipal wastewater was studied. A selected number of clones of microorganisms present in the biofilm were identified. Biotransformation products were tentatively identified and the toxicity of the treated effluent was assessed. Microbial samples were DNA-sequenced and subjected to phylogenetic analysis in order to confirm the identity of the microorganisms present and determine the microbial diversity. The analysis demonstrated that the wastewater was populated by a bacterial consortium related to different members of Proteobacteria, Firmicutes, and Nitrisporae. The optimum removal values of the ICM achieved were 79 % for IOX and 73 % for DTZ, whereas 13 biotransformation products for IOX and 14 for DTZ were identified. Their determination was performed using ultra-performance liquid chromatography-tandem mass spectrometry. The toxicity of the treated effluent tested to Daphnia magna showed no statistical difference compared to that without the addition of the two ICM. The MBBR was proven to be a technology able to remove a significant percentage of the two ICM from urban wastewater without the formation of toxic biodegradation products. A large number of biotransformation products was found to be formed. Even though the amount of clones sequenced in this study does not reveal the entire bacterial diversity present, it provides an indication of the predominating phylotypes inhabiting the study site.

Biodegradation of pharmaceuticals in hospital wastewater by a hybrid biofilm and activated sludge system (Hybas)

“…Also, MBBRs were shown to degrade iohexol and diatrizoic acid from wastewater (Hapeshi et al, 2013). As the hydraulic retention time in the present study was similar to Kovalova et al (2012), it seems that the key to degrade ICM is more likely to rely on the biomass characteristics.…”

“…As the hydraulic retention time in the present study was similar to Kovalova et al (2012), it seems that the key to degrade ICM is more likely to rely on the biomass characteristics. In this case the determining factor appears to be the presence of different types of biofilm in the treatment system (Escolà Hapeshi et al, 2013;this study). In this study biodegradation was detected in the sludgeonly reactor (H1).…”

“…ICM are usually persistent to conventional WWTP treatment as well as realistic ozone treatment (Kovalova et al, 2012;Hapeshi et al, 2013). MBR treatment showed negligible removals of ICM from hospital wastewater, except for iopromide which was removed up to 31% (Kovalova et al, 2012).…”

“…(Bester and Schafer, 2009;Heberer et al, 2004;Hijosa-Valsero et al, 2011;Janzen et al, 2009;Li et al, 2014;Reungoat et al, 2011;Zearley and Summers, 2012). Along with such biofilm technologies, MBBR also seemed to be a promising solution to remove micro-pollutants, which cannot be removed with activated sludge treatment (Hapeshi et al, 2013;Zupanc et al, 2013;Falås et al, 2012Falås et al, , 2013.…”

Comparison of the MBBR denitrification carriers for advanced nitrogen removal of wastewater treatment plant effluent

“…The carriers must have high mechanical strength, high corrosion wear resistance, good suspendability, large specific surface area, high surface roughness, and easy for microbial adhesion, etc. Polyethylene (Dupla et al 2006;Martina et al 2010;Rusten et al 2006;Stinson et al 2009), polypropylene (Dupla et al 2006), polyurethane foams (Chu and Wang 2011), and haydite (Delnavaz et al 2010;Wei et al 2011) are widely used as MBBR carriers to treat reject water (Zekker et al 2012), landfill leachate (Welander et al 1998), domestic sewage (Hapeshi et al 2013;Martina et al 2010;Mases et al 2010;Stinson et al 2009), etc. Microorganisms with denitrification function are widely distributed, which are independent of system differentiation; therefore, 16S rRNA gene probe is not suitable for environmental denitrification community analysis (Scala and Kerkhof 1998). As an alternative approach, functional genes are applied to investigate the denitrifican structure and diversity in environmental samples.…”