Aeration followed by rapid sand filtration is the conventional method for drinking water production from groundwater. During aeration, methane is stripped from the water, whereas microbial and biochemical processes in the sand filter facilitate the removal of iron, ammonium, and manganese. Due to its high greenhouse gas potential, the released methane significantly contributes to the carbon footprint of drinking water production.
Our study explores the possibility of mitigating methane emissions by applying biological methane oxidation as a sustainable alternative to stripping. We compared the traditional approach involving aeration followed by primary and secondary rapid sand filters, and an alternative method with a primary dry trickling filter and a subsequent secondary rapid sand filter. A multi-omics approach, integrating 16S rRNA gene amplicon sequencing, metagenomics, and metaproteomics, was employed to gain a comprehensive understanding of the microbial communities responsible for contaminant removal.
We found that in the alternative approach, the methane entering the trickling filter selected for a dominant population of methane-oxidizing bacteria, which successfully removed methane. As a result, ammonium and manganese removal were shifted to the secondary rapid sand filter. This contrasts the traditional treatment line, where almost no methane-oxidizing bacteria where present, and ammonium and manganese were successfully removed already in the primary rapid sand filter. Interestingly, different nitrogen cycle microorganisms facilitated ammonium removal in the rapid sand filters of the different treatment lines. Complete ammonia oxidizers of the genus Nitrospira dominated nitrification in the traditional treatment, while this was catalyzed by Candidatus Nitrotoga and Nitrosomonas in the trickling filter treatment line.
In conclusion, our research indicates biological methane removal as a viable alternative to aeration-based stripping, offering a more sustainable method for drinking water production from methane-containing groundwater. Less...