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Laura Brophy

PhD Researcher
Dept. of Civil, Structural & Environmental Engineering


Impacts of domestic wastewater treatment systems on surface water

Keywords: On-site domestic wastewater treatment system; phosphorus; poorly permeable catchments; surface water contamination; catchment hydrology, domestic wastewater fingerprinting.


Domestic Wastewater Treatment Systems (DWWTSs), commonly referred to as septic tanks, constitute an important part of Ireland’s wastewater infrastructure. According to official census data (2011) there are 438,000 of these systems currently in use throughout the country. The correct operation of DWWTSs is largely dependent upon the presence of deep, unsaturated subsoil beneath the percolation area. However, digital mapping has indicated that >140,000 DWWTSs are located in areas where there is a very high risk of untreated domestic wastewater entering nearby surface waters due to the fact that they have been constructed in areas of poorly drained subsoil or shallow, impermeable bedrock.

This research project aims to quantify the impacts of DWWTS on water quality in poorly-drained catchments, particularly with respect to phosphorus loading. Other analytes include ammonia, nitrite, nitrate, total nitrogen, total coliforms, E.coli and enterococci. The research will also examine the applicability of a number of biological and chemical tracers of domestic effluent in the receiving environment, in order to develop a tiered-approach to the investigation of DWWTS contamination in surface waters, which may be of use to environmental monitoring agencies.


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