Innovative on-site wastewater treatment systems (OWTS) are a promising solution to problems caused by excessive fixed nitrogen in areas without centralized wastewater treatment (sewers and treatment plants). One such design is a passive nitrogen-removing biofilter (NRB), a partially engineered system that capitalizes on natural microbial processes to remove nitrogen from wastewater. After settling in a septic tank, wastewater is evenly dispersed into an NRB built under a homeowner’s yard. The hypothesis is that physical characteristics of NRB design affect microbial community structure, promoting the desired processes. The top sandy layer provides aerobic conditions with little available carbon to promote nitrification and the bottom woodchip/sand layer provides anaerobic conditions with a long-lasting carbon source to promote denitrification. This hypothesis predicts that the microbial assemblage in the nitrification layer will be distinct from the assemblage in the denitrification layer. To test this prediction, aged matrix from a full-scale test NRB was repacked into lab-scale microcosms simulating intact NRB structure and exposed to artificial wastewater for two weeks. The microcosms allowed us to document the oxygen availability within each layer of the NRB and to collect matrix samples from consistently oxic, anoxic, and oscillatory zones. The matrix microbial community was characterized by Illumina high-throughput sequencing of 16S rRNA gene amplicons. Sequences were grouped into operational taxonomic units (OTUs) at 97% identity, roughly species level. Ordination plots of the dissimilarity between samples (UniFrac measure) showed a distinct separation between the nitrification and denitrification microbial assemblages with samples from the oscillatory zone intermediate. This observation supports the hypothesis that physical characteristics of NRBs influence microbial community structure. Preliminary results reveal that nitrifiers and denitrifiers are present throughout the NRB, but the relative abundance of specific genera differ between nitrification and denitrification zones. The presentation will explore which taxa are driving the differences between the nitrification and denitrification layers in NRBs and the insight this provides into NRB function.

Characterization of the microbial community driving on-site wastewater treatment in nitrogen removing biofilters (NRBs)

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.