Modelling the viability of heat recovery from underground pipes

Modelling wastewater temperature variations in a network of 3048sewer pipes was achieved in this project. Recovering heat from sewers presents attractive options for producing clean energy. However, heat recovery from sewerage may result in wastewater temperature drops whichmay reduce the influent temperature at the wastewater treatment plant (WWTP). This drop in the WWTP influent temperature may result in the degradation ofthe biological treatment stage. Therefore, it is vital to predict the impact of recovering heat from sewers on the wastewater temperature. Sewer temperatures along with hydraulic data were measured for up to a year in four differentBelgian sites. The measured data was utilised to calibratea deterministic sewer pipemodelthat estimatesthe wastewater temperature variation along the sewer pipe profiles. The latter model was calibrated using data from two sites and then validated using independentdata from the other two sites. The sewer pipe model was then further developed to model wastewater temperature variations in a large (3048 pipe)network. The large network model was tested byimplementing threedifferent heat recovery scenarios. It was observed that9MW may be recovered from the 3048pipenetwork, serving a catchment with a population equivalent of 79500 inhabitants,without impacting negatively on the biological processes