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Project title

Refined estimates of atmospheric emissions associated with wastewater treatment processes for Ireland

Primary Funding Agency

Environmental Protection Agency

Co-Funding Organisation(s)

n/a

Lead Organisation

University of Dublin, Trinity College (TCD)

Lead Applicant

Laurence Gill

Project Abstract

The research project, WASTEMISSION, aims to improve estimates of Ireland’s greenhouse gas (GHG) and air pollution emissions associated with wastewater treatment from both centralised and decentralised (predominantly septic tanks for single houses) systems. Ireland is currently failing to meet its GHG obligations and the gap between its annual GHG emissions and allocated allowances is becoming larger. Hence, a very large reduction in emissions is required across all sectors if Ireland is to meets its climate ambitions as set out in the Climate Action and Low Carbon Development (Amendment) Bill 2021. The EPA is responsible for compiling the National Inventory Report of GHG emissions for the European Commission and the United Nations Framework Convention on Climate Change (UNFCCC). Currently, the main GHGs from wastewater treatment, methane (CH4) and nitrous oxide (N2O) are estimated based on generic organic and nitrogenous (protein) waste inputs to treatment facilities per unit population: i.e. mainly assessed via a Tier 1 methodology. This project will expand knowledge of wastewater related GHG and other air pollutant emissions databases for Ireland, augmenting higher tier methodologies into inventory and projection analyses and also suggesting and assessing the impact of future mitigation and abatement strategies. This will be achieved by combination of desk study of international research on emissions on centralised wastewater treatment plants as well as some direct gas flux measurements on both centralised and on-site systems in Ireland. The international review will collate results from studies on different treatment process types (primary, secondary, tertiary and sludge treatment). Each study will be normalised according to wastewater flows and loads and other key process factors. These emission factors will then be used against a database of all centralised treatment plants (municipal and industrial) and their respective process stages in Ireland to calculate cumulative emissions. A couple of representative municipal and industrial treatment plants will also be monitored directly to provide some sort of validation against the normalised loads. For the on-site wastewater treatment systems, which serve on third of the Irish population, it is proposed to focus more effort on measurements in the field to build on the work recently carried out in Ireland by the TCD Environmental Engineering research team and given how few studies have been carried out internationally. The field measurements will focus on fluxes of CH4 and N2O from septic tanks, packaged treatment systems and vent fluxes which showed to have the highest fluxes. Cumulative fluxes from on-site systems for the country will then be calculated based on the data from the latest census on the number of systems in the country and whether they are septic tank or packaged treatment systems. The project will provide a synthesis of suggested emission factors for different wastewater treatment processes (municipal industrial and on-site) for comparison against the current estimates in Ireland’s National Inventory Reporting. These will also reveal where the main CH4 and N2O emissions are likely to be occurring and via which microbial pathways and strategies will be presented as to how these might be mitigated.

Grant Approved

�199,546.30

Research Hub

Climate Change

Research Theme

n/a

Start Date

01/03/2023

Initial Projected Completion Date

28/02/2025