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Christopher Fennell

PhD Researcher
Dept. of Civil, Structural & Environmental Engineering



The impact of domestic wastewater treatment system effluent on private water wells: An evaluation of contamination fingerprinting techniques

Keywords: On-site domestic wastewater treatment system; groundwater; private wells; contamination tracers.


Approximately 162,000 Irish households depend on private water sources, mainly wells, for their water supply. Sampling studies of these wells for the presence of faecal indicator bacteria have shown that approximately 30% are polluted, at least intermittently, with one of the main sources of microbial pathogens believed to be domestic wastewater treatment systems (DWWTS), mainly septic tanks. DWWTS are employed by approximately 438,000 dwellings across Ireland.


However, as faecal indicators are not source-specific, identifying whether the contamination is of human or animal waste origin is difficult and has not been carried out previously.


Building on previous research on the extent of private well contamination in Ireland, this research is employing a range of techniques for identifying specific sources of well contamination and, particularly, the extent of the pollution from DWWTS as opposed to agricultural sources, which are also a significant issue in rural Ireland.


Private wells are being used to apply and evaluate a range of contamination fingerprinting techniques including fluorescent whitening compounds, faecal sterols, anion ratios, emerging organic compounds as well as a range of microbial source tracking (MST) techniques.


Project Supervisors: Associate Prof. Bruce Misstear & Prof. Laurence Gill