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Jan Spriet

PhD Researcher
Dept. of Civil, Structural & Environmental Engineering


Drain Water Heat Recovery

Keywords: Waste water systems; Heat recovery; Heat pumping systems; Energy Recovery.


The availability and quality of water and energy resources are closely linked to human lifestyle and the development of society. These two resources are often combined to create comfortable space temperature, and generate hot water for washing and cleaning. Thermal energy accounts for a little under one third of the primary energy consumption in Ireland, and is still largely produced by fossil fuels. Furthermore a large part of thermal energy delivered to buildings is simply lost through hot wastewater, flushed through the drain.



The idea behind this research is to reduce thermal energy consumption in both residential and commercial buildings, by recovering the heat that is now wasted through the drain, and/or providing the possibility to use less greenhouse gas intensive thermal energy production methods (a heat pump in this case). A combination of both strategies has yet to be attempted, furthermore there’s little or no knowledge and literature available on recovery system in septic tanks, which are installed in around 30% of the dwellings in Ireland, and their impact on the efficient operation of these on-site waste water treatment units.



Within the framework of Dŵr Uisce programme, my contribution as a Ph.D. student at Trinity College Dublin falls into three interrelated areas of research:

  1. Studying the potential impact of such waste and drain water heat recovery systems on the thermal energy landscape and the environmental impact of thermal energy production. This desk study will be complemented by a business case and business plan development, and a study of the financial viability of this technology.
  2. The design and modelling of such heat recovery units for both residential and commercial buildings, with special attention to septic tank systems. And installing and testing a prototype drain water heat recovery system.
  3. Delivery of design guidelines and decision support systems to enable future development and implementation of such technology.


Project Supervisors: Dr. Aonghus McNabola