Microbial communities controlling methane and nutrient cycling in leach field soils

Cristina P Fernández-Baca; Amir-Eldin H Omar; Jesse T Pollard; Ruth E Richardson

doi:10.1016/j.watres.2018.12.036

Microbial communities controlling methane and nutrient cycling in leach field soils

Water Res. 2019 Mar 15:151:456-467. doi: 10.1016/j.watres.2018.12.036. Epub 2018 Dec 27.

Authors

Cristina P Fernández-Baca¹, Amir-Eldin H Omar², Jesse T Pollard³, Ruth E Richardson³

Affiliations

¹ Department of Civil and Environmental Engineering, 220 Hollister Hall, Cornell University, Ithaca, NY, USA. Electronic address: cpf45@cornell.edu.
² Department of Molecular Biology and Genetics, 107 Biotechnology Building, Cornell University, Ithaca, NY, USA.
³ Department of Civil and Environmental Engineering, 220 Hollister Hall, Cornell University, Ithaca, NY, USA.

PMID: 30640159
DOI: 10.1016/j.watres.2018.12.036

Abstract

Septic systems inherently rely on microbial communities in the septic tank and leach field to attenuate pollution from household sewage. Operating conditions of septic leach field systems, especially the degree of water saturation, are likely to impact microbial biogeochemical cycling, including carbon (C), nitrogen (N), and phosphorus (P), as well as greenhouse gas (GHG) emissions to the atmosphere. To study the impact of flooding on microbial methane (CH₄) and nutrient cycling, two leach field soil columns were constructed. One system was operated as designed and the other was operated in both flooded and well-maintained conditions. CH₄ emissions were significantly higher in flooded soils (with means between 0.047 and 0.33 g CH₄ m^-2 d^-1) as compared to well-drained soils (means between -0.0025 and 0.004 g CH₄ m^-2 d^-1). Subsurface CH₄ profiles were also elevated under flooded conditions and peaked near the wastewater inlet. Gene abundances of mcrA, a biomarker for methanogens, were also greatest near the wastewater inlet. In contrast, gene abundances of pmoA, a biomarker for methanotrophs, were greatest in surface soils at the interface of CH₄ produced subsurface and atmospheric oxygen. 16S rRNA, mcrA, and pmoA amplicon library sequencing revealed microbial community structure in the soil columns differed from that of the original soils and was driven largely by CH₄ fluxes and soil VWC. Additionally, active microbial populations differed from those present at the gene level. Flooding did not appear to affect N or P removals in the soil columns (between 75 and 99% removal). COD removal was variable throughout the experiment, and was negatively impacted by flooding. Our study shows septic system leach field soils are dynamic environments where CH₄ and nutrients are actively cycled by microbial populations. Our results suggest proper siting, installation, and routine maintenance of leach field systems is key to reducing the overall impact of these systems on water and air quality.

Keywords: Methane; Methanogen; Methanotrophs; Onsite wastewater treatment (OWTS); Septic leach field system; Wastewater.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Methane*
Microbiota*
Nutrients
RNA, Ribosomal, 16S
Soil

Substances

RNA, Ribosomal, 16S
Soil
Methane