Nitrogen Removal Capacity of Microbial Communities Developing in Compost- and Woodchip-Based Multipurpose Reactive Barriers for Aquifer Recharge With Wastewater

Abstract

Global water supplies are threatened by climate changes and the expansion of urban areas, which have led to an increasing interest in nature-based solutions for water reuse and reclamation. Reclaimed water is a possible resource for recharging aquifers, and the addition of an organic reactive barrier has been proposed to improve the removal of pollutants. There has been a large focus on organic pollutants, but less is known about multifunctional barriers, that is, how barriers also remove nutrients that threaten groundwater ecosystems. Herein, we investigated how compost- and woodchip-based barriers affect nitrogen (N) removal in a pilot soil aquifer treatment facility designed for removing nutrients and recalcitrant compounds by investigating the composition of microbial communities and their capacity for N transformations. Secondary-treated, ammonium-rich wastewater was infiltrated through the barriers, and the changes in the concentration of ammonium, nitrate, and dissolved organic carbon (DOC) were measured after passage through the barrier during 1 year of operation. The development and composition of the microbial community in the barriers were examined, and potential N-transforming processes in the barriers were quantified by determining the abundance of key functional genes using quantitative PCR. Only one barrier, based on compost, significantly decreased the ammonium concentration in the infiltrated water. However, the reduction of reactive N in the barriers was moderate (between 21 and 37%), and there were no differences between the barrier types. All the barriers were after 1 year dominated by members of Alphaproteobacteria, Gammaproteobacteria, and Actinobacteria, although the community composition differed between the barriers. Bacterial classes belonging to the phylum Chloroflexi showed an increased relative abundance in the compost-based barriers. In contrast to the increased genetic potential for nitrification in the compost-based barriers, the woodchip-based barrier demonstrated higher genetic potentials for denitrification, nitrous oxide reduction, and dissimilatory reduction of nitrate to ammonium. The barriers have previously been shown to display a high capacity to degrade recalcitrant pollutants, but in this study, we show that most barriers performed poorly in terms of N removal and those based on compost also leaked DOC, highlighting the difficulties in designing barriers that satisfactorily meet several purposes.

Assessing the Fate of Benzophenone-Type UV Filters and Transformation Products during Soil Aquifer Treatment: The Biofilm Compartment as Bioaccumulator and Biodegrader in Porous Media

“…That is, the presence of the reactive barrier enhanced the biological activity and the organic carbon oxidation, which is consistent with observations of Valhondo et al ,, Recall that the reactive barrier had been installed 2 years before the slug injection, and one of its goals was to release DOC to favor reducing conditions. By the end of this 2-year period, it was expected that this release had been largely depleted. , Therefore, we attribute the higher degradation in the CT system to a richer bacterial activity as was established in Hellman et al The greater reactivity in CT is also supported by the Li + breakthrough curves (Figure S2). The tail of Li + lasts longer than that of CE, and more so for the CT, while the peak arrivals are similar, which reflects both that Li + is adsorbed and that adsorption is noninstantaneous (otherwise the Li + peak arrival would have been retarded).…”

Pathways and Efficiency of Nitrogen Attenuation in Wastewater Effluent Through Soil Aquifer Treatment

“…Lower ε 15 N-NH 4 + (in absolute values) could be explained by some potential contribution of plant assimilation in the systems. Hellman et al (2022) suggested that the mixed vegetation at the infiltration area contributed to the NH 4 + attenuation in the SAT-PRB system at the beginning of the experiment. The assimilation of N-NH 4 + by different plant species reported by Emmerton et al (2001), estimated an increase in ẟ 15 N-NH 4 + of 2‰.…”

“…where Fidel et al, 2018;Wang et al, 2015) or plant assimilation (Desimone and Howes, 1998;Lusby et al, 1998) or due to contemporaneous production and consumption of nitrates (coupled nitrification-denitrification reaction) (Kim et al, 1997;Lusby et al, 1998; or Anammox reactions (Burgin and Hamilton, 2007;Castro-barros et al, 2017). In fact, genetic analyses of the microbial communities present in the barriers demonstrate a potential for all these microbially mediated processes to occur (Hellman et al, 2022).…”

Spatial and temporal changes in microbial communities and greenhouse gas emissions in a denitrifying woodchip bioreactor at low water temperatures

“…Frequent OTUs were found separately for water and woodchips samples as described in Hellman et al (2022) and Saghaï et al (2021), resulting in 755 and 1608 core OTUs in the woodchips and water samples, respectively that retained 88.2% and 93.3% from the total OTU abundances in respective datasets. Phylogenetic diversity (Faith, 1992) of the communities was estimated using estimate_pd function in "btools" package.…”

“…The 16S rRNA sequences were processed as described in Hellman et al (2022), except that the non-redundant reference database SILVA version 138 was used to classify representative OTUs. SINA (Pruesse et al, 2012) was used to align nucleotide sequences of the representative OTUs to the SILVA database, and FastTree (Price et al, 2009) with the Jukes-Cantor and CAT model (Jukes and Cantor, 1969) was used to construct a phylogenetic tree from the aligned sequences.…”