Biokinetic Characterization of Methane Oxidizing Microbiomes Co-metabolizing Trace Organic Chemicals

Abstract: The presence of organic micropollutants (OMPs) in wastewater effluents is concerning, as they pose a threat to human and aquatic health. Biodegradation via methane-oxidizing bacteria (MOB) is an attractive option, as the method is cheap and effective. MOB can co-metabolize a variety of substrates, there among organic micropollutants. Methane-oxidizing microbiomes (MOMs) were cultivated with different SRT, methane loading rate, O2:CH4 ratio and nitrogen sources. The MOMs were spiked with OMPs for adaptation. Most of the MOMs generated similar results with specific growth rates of 0,40-0,66 d-1 and biomass yields on methane of 0,32-0,64 g CDW∙g CH4-1. The MOMs with higher methane loading had the highest methane uptake rates, as well as the highest yields on nitrogen. The MOMs grown on nitrate instead of ammonia had higher methane and nitrogen uptake rates. The MOMs with 15 days SRT, high methane loading, 3:2 O2:CH4 ratio and nitrate as the nitrogen source generated the highest biokinetic values overall. The MOMs degraded sulfamethoxazole (SMX) between 81-85%, reaching removal rates of 4,5-5,3 L∙g-1∙d-1. Metoprolol, diclofenac and dimethyl sulfide were moderately degraded between 22-50%. The degradation of SMX generated higher removal rates than some previous studies, there among degradation via activated sludge and membrane bioreactors. The MOMs that had not been adapted to OMPs had poor removal efficiencies in general, highlighting the importance of adaptation. The MOMs with low methane loading generated the highest removal efficiencies. A microbial community analysis is needed to further conclude how the communities differ. Further research is needed to grasp why the high methane loading bacteria had lower removal efficiencies while simultaneously oxidizing methane to a higher extent.