Methanotrophic contribution to biodegradation of phenoxy acids in cultures enriched from a groundwater-fed rapid sand filter
Drinking water supply is in many parts of the world based on groundwater. Groundwater often contains methane, which can be oxidized by methanotrophs upon aeration. Sand from rapid sand filters fed with methane-rich groundwater can remove some pesticides (Hedegaard and Albrechtsen in Water Res 48:71–81, 2014). We enriched methanotrophs from filter sand and investigated whether they could drive the degradation of various pesticides. To enrich for methanotrophs, we designed and operated four laboratory-scale, continuously methane-fed column reactors, inoculated with filter sand and one control column fed with tap water. When enrichments were obtained, methane was continuously supplied to three reactors, while the fourth was starved for methane for 1 week, and the reactors were spiked with ten pesticides at groundwater-relevant concentrations (2.1–6.6 μg/L). Removal for most pesticides was not detected at the investigated contact time (1.37 min). However, the degradation of phenoxy acids was observed in the methanotrophic column reactor starved for methane, while it was not detected in the control column indicating the importance of methanotrophs. Phenoxy acid removal, using dichlorprop as a model compound, was further investigated in batch experiments with methanotrophic biomass collected from the enrichment reactors. Phenoxy acid removal (expressed per gram of matrix sand) was substantially improved in the methanotrophic enrichment compared to parent filter sand. The presence of methane did not clearly impact dichlorprop removal but did impact mineralization. We suggest that other heterotrophs are responsible for the first step in dichlorprop degradation, while the subsequent steps including ring-hydroxylation are driven by methanotrophs.
KeywordsMethanotrophs Drinking water Pesticides Phenoxy acids Removal
This work was funded by project MIcrobial REmediation of contaminated SOil and WAter resources (MIRESOWA, DSF - The Danish Strategic Research Council grant number 2104-08-0012) and the Grundfos prize to Hans-Jørgen Albrechtsen.
Compliance with ethical standards
Conflict of interest
Aikaterini Papadopoulou declares that she has no conflict of interest. Mathilde J. Hedegaard declares that she has no conflict of interest. Arnaud Dechesne declares that he has no conflict of interest. Hans-Jørgen Albrechtsen declares that he has no conflict of interest. Sanin Musovic declares that he has no conflict of interest. Barth F. Smets declares that he has no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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