Characterization of Bacterial and Archaeal Communities by DGGE and Next Generation Sequencing (NGS) of Nitrification Bioreactors Using Two Different Intermediate Landfill Leachates as Ammonium Substrate

Abstract

Nitrification-denitrification is an environmentally friendly and cost-effective way to treat landfill leachates. Special attention has been given to the nitrification step, usually the limiting one due to its special sensitivity to environmental factors. Here, the effect of the acclimatization of the nitrifying biomass to two different intermediate landfill leachates with different salt concentrations, COD and BOD5 has been studied. Despite the complete nitrification being successfully performed, the specific nitritation rates were reduced after the biomass adaptation to both landfill leachates caused by the presence of heavy metals and the high salt concentration. NGS analysis of the biomass samples revealed that Proteobacteria (48.5%), Actinobacteriota (14.4%) and Chloroflexi (9.5%) were the dominant phyla in the non-adapted biomass. The leachate feeding led to a decrease in OTU diversity and favored the growth of the phyla Bacteroidetes (27.2%), Euryarchaeota (26.6%) and Proteobacteria (20.0%) accounting for more than 70% of relative abundance. Several OTUs capable of performing the nitritation belong to the Xanthobacteraceae and the Xanthomonadaceae families, the Saccharimonadales order, and the genus Nitrosomonas, Nitrosospira and Paracoccus. In the nitratation process, the Xanthobacteraceae family and Lautropia and Nitrolancea genera were found.