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Celia Somlai

PhD Researcher
Dept. of Civil, Structural & Environmental Engineering


Emission of GHGs from on-site wastewater treatment systems

Keywords:On-site domestic wastewater treatment system; flux chambers; greenhouse gases; methane; carbon dioxide; nitrous oxide; septic tank; soil attenuation system, soil treatment unit.


Approximately one third of the population of Ireland relies on on-site domestic wastewater systems (DWWTs) to treat their wastewater. The DWWTs most commonly composed of a septic tank and a soil treatment unit for effluent dispersal. By microbial mediated processes, the influent organic matter in septic systems is converted into carbon dioxide (CO2) and methane (CH4); nitrous oxide (N2O) can be formed from the partial denitrification of nitrate.

Considering the large number of DWWTs in Ireland, septic systems are potential significant sources of greenhouse gas (GHG) emissions. The existing inventories of GHG emissions from septic systems are lacking direct field measurement and based on assumption of the conversion rate of organic matter entering the systems.

The main objectives of this project is quantifying and qualifying the on-site production of GHGs within the treatment units and the percolation area in Ireland using Ultraportable Greenhouse Gas Analyser (Los Gatos Research Inc., Mountain View, CA, U.S.A) integrated into LI-8100A Automated Soil Gas Flux System (Li-Cor®).

Somlai-Haase, C., Knappe, J. and Gill, L., 2017. Carbon dioxide emissions from a septic tank soakaway in a northern maritime climate. Science of The Total Environment, 586, pp.485-491.


Project Supervisor: Prof. Laurence Gill