Analysing wastewater temperature development in a sewer system as a basis for the evaluation of wastewater heat recovery potentials

Wastewater contains significant quantities of thermal energy. Consequently, heat recovery in sewer systems can provide urban areas with an additional source of renewable energy for heating of buildings. However, certain treatment processes in a wastewater treatment plant are temperature-sensitive. From a water protection perspective it is therefore imperative, that heat recovery in sewer systems does not negatively affect the performance of the wastewater treatment. With regard to practical implication the question arises, where to find the locations best suitable for wastewater heat recovery in sewer systems. Hereby, suitability is characterised by meeting both the energy supply and water pollution control requirements. This article introduces a methodological framework (procedure) to evaluate the suitability of a potential heat recovery site integrating both perspectives. The framework incorporates decision support criteria and planning principles for energy planners and water authorities. Application in a case study proved practicability of the procedure as well as of the criteria and principles. In addition, it also delivered comprehensive information on the spatial and temporal wastewater temperature development in the regarded sewer system. (C) 2016 Elsevier B.V. All rights reserved.