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

Xiyang Dong,Guido Lens,Rainer U Meckenstock,Daniel Schunk,Mona Rahmatullah,Leonard E Bäcker

doi:10.1186/s13568-019-0827-0

Xiyang Dong, Guido Lens + Show 4 more

Open Access

https://doi.org/10.1186/s13568-019-0827-0

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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 13C-labelled bicarbonate. By monitoring the release of 12C–CO2 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.

Highlights

Dissolved organic carbon (DOC) is composed of complex mixtures of heterogeneous organic compounds derived from the decay of organic matter and other sources
The removal of DOC by the biological activated carbon (BAC) filters developed in three stages (Korotta-Gamage and Sathasivan 2017a; Simpson 2008)
So far, there are only indirect methods available to measure microbial degradation activities of organic carbon adsorbed to solid matrices

Summary

Introduction

Dissolved organic carbon (DOC) is composed of complex mixtures of heterogeneous organic compounds derived from the decay of organic matter and other sources. In drinking water production from surface water such as rivers and barrage lakes, it is important to remove the DOC because it affects the drinking water quality and performance of water treatment processes (Korotta-Gamage and Sathasivan 2017a, b; Li et al 2017). Part of the DOC is biodegradable dissolved organic carbon (BDOC) that can serve as substrate for bacterial. The degradation rate of adsorbed organic carbon becomes an important parameter in the purification process, which is, mostly not measured in drinking water production plants. This is partly due to the lack of suitable and reliable methods to assess biodegradation processes on solid matrices. Culture-independent molecular tools have shown that highly diverse microbial communities of bacteria and archaea populate BAC filters (Gulay et al 2016; Vignola et al 2018)

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