Quantification of microbial degradation activities in biological activated carbon filters by reverse stable isotope labelling

Abstract

Biological activated carbon (BAC) filters are frequently used in drinking water production for removing dissolved organic carbon (DOC) via adsorption of organic compounds and microbial degradation. However, proper methods are still missing to distinguish the two processes. Here, we introduce reverse stable isotope labelling (RIL) for assessing microbial activity in BAC filters. We incubated BAC samples from three different BAC filters (two granular activated carbon- and one extruded activated carbon-based) in a buffer amended with 13 C-labelled bicarbonate. By monitoring the release of 12 C–CO 2 from the mineralization of DOC, we could demonstrate the successful application of RIL in analysing microbial DOC degradation during drinking water treatment. Changing the water flow rates through BAC filters did not alter the microbial activities, even though apparent DOC removal efficiencies changed accordingly. Microbial DOC degradation activities quickly recovered from backwashing which was applied for removing particulate impurities and preventing clogging. The size distributions of activated carbon particles led to vertical stratification of microbial activities along the filter beds. Our results demonstrate that reverse isotope labelling is well suited to measure microbial DOC degradation on activated carbon particles, which provides a basis for improving operation and design of BAC filters.

Soothsaying DOM: A Current Perspective on the Future of Oceanic Dissolved Organic Carbon

“…However, bulk DOC does not permit distinction between the different carbon pools and uniformly labeled substrates omit the understanding of the fate of single carbon atoms within a molecule that are being differently used during uptake, biosynthesis, molecular transformation, and final release of DIC. Therefore, to specifically trace the microbial conversion of DOC to cellular biomolecules and metabolites or microbial remineralization of DOC to CO 2 , novel approaches based on position-specific and dual-isotope stable isotope probing (SIP), lipid radioisotope probing (RIP), and reversed isotope labeling (RIL) have been adapted from routine labeling techniques (Figure 3) (Wegener et al, 2012;Dippold and Kuzyakov, 2013;Kellermann et al, 2016;Dong et al, 2017Dong et al, , 2019Evans et al, 2018Evans et al, , 2019Aepfler et al, 2019).…”

“…Lipid radioisotope probing has been similarly applied to better understand lipid biosynthetic pathways in marine planktonic archaea (Evans et al, 2018). Natural DOM and environmental organic compounds that are not available in a stable isotope or radiolabeled form are accessible to turnover studies using RIL, in which a pool of 13 C-labeled DIC is continuously diluted during microbial degradation of a specific organic substrate or DOM at natural carbon isotope abundance (Dong et al, 2017(Dong et al, , 2019. Thus, the change in the isotopic composition of DIC enables quantification of microbial remineralization by mass balance calculations.…”

Microbial Degradation Rates of Natural Bitumen

“…In the natural environment, biodegradation is assumed to be even slower or sometimes completely inhibited due to temperature and other abiotic factors. Therefore, we applied the relatively new method of reverse stable isotope labeling, enabling the measurement of degradation of unknown carbon sources even at extremely low rates. − This robust and sensitive method is based on the dilution of a 13 C-labeled bicarbonate buffer with nonlabeled carbon dioxide from biodegradation of hydrocarbons at natural isotopic abundance …”

Biofiltration for treatment of recent emerging contaminants in water: Current and future perspectives

“…Also, biofilms could play a role in biodegradation (utilization of substrates for growth) and adsorption of contaminants into biomass without degradation, both of which would need more equations than just growth or diffusion kinetics into modeling (Shen et al, 2012). Isotope labeling could also be used to determine stratification of microbial activities inside the biofilms, and this technique can also be applied to distinguish between adsorption REVIEW Water Environment Research • 972-992, 2021 and biodegradation inside BAC filters (Dong, Bäcker, et al, 2019).…”