Modelling Of Thermal Energy Balance In Sewer Systems

Warm water is an important factor in the water and energy nexus. The energy used to produce warm tap water is often 10 times higher than the operational energy to produce and distribute drinking water and to collect and treat wastewater together. Once used in a shower, bath or laundry machine, the hot water is disposed into the sewer system. For modern homes in The Netherlands this is 30-50 % of the total heat loss. Heat recovery from sewer systems may therefore be an interesting option to reduce water use related energy. In this study a model was developed to predict the temperature and heat available in the sewer systems. The model includes three submodels. The heart of the model is formed by an existing sewer model (SOBEK1). This model is extended with a water quality module that includes an energy balance for the sewer system (submodel 2). The heat balance includes convective heat transport and heat loss into the surrounding soil. Finally, the third model is a model to describe the drinking water demand (SIMDEUM)2. This model simulates demand patterns of water use in homes and office buildings. The model can be used to predict volume and temperature of discharges of wastewater into the sewer. Combining these three models can predict dynamic and spatial temperature variations in sewer systems. The model can be used find the optimum position for installing heat recovery equipment in sewer systems. Experimental validation by measurements in a sewer system in Amsterdam have indicated that the expected wastewater temperatures in the sewers could be confirmed. The presentation will describe the model and the results of the experimental validation. 1http://www.deltaressystems.com/hydro/product/108282/sobek-suite 2 Blokker, E.J.M. (2010) Stochastic water demand modelling for a better understanding of hydraulics in water distribution networks. Ph.D., Delft University of Technology, Delft