Abstract
To counteract climate change, the application of renewable energy sources and their efficient use are of crucial importance. In this context, wastewater has also gained increased attention in recent years. For decades, wastewater treatment plants have applied the heat from digester gas combustion to supply internal demands. However, in the context of efficient energy use the question arises: can using high temperature heat for supplying low temperature demand still be considered the best option? This article presents an innovative approach to covering wastewater treatment plant (WWTP) internal demand with low temperature wastewater heat recovery, making thermal energy from digester gas combustion available for feed-in to a local high temperature district heating network. The presented feasibility study was carried out in an Austrian municipality and investigates the heat balance, the economic risk, climatic benefits and the social aspects of the suggested approach. The practical implementation of the novel approach was planned in two steps. First, the WWTP should be connected to the district heating network to enable the feed-in of excess heat. Second, the WWTP internal heat supply should be modified and based on wastewater heat recovery from the effluent. Due to the promising results of the feasibility study, the first step was realized in summer 2020. The second and final step was initiated in 2021.
Highlights
Climate change is one of the great challenges of our times
In this context, achieving the highest possible degree of electric energy self-sufficiency usually has been the supposed objective at many wastewater treatment plants (WWTPs). The reason for this singular focus can be found in the fact that electricity generation at WWTPs has always been rather limited while thermal energy has often been available in excess (Kretschmer et al [3])
This applies, above all, for WWTPs with anaerobic sewage sludge treatment, where the produced digester gas/biogas has been used for the generation of electric and thermal energy by combined heat and power (CHP) units for decades (Elías-Maxil et al [4])
Summary
Climate change is one of the great challenges of our times. Efficient energy usage and the substitution of fossil energy sources by renewable ones are considered key principles to counteract global warming (European Commission [1]). To date, the main driver for related activities appears to be the reduction of energy costs rather than any climate protection ambitions. In this context, achieving the highest possible degree of electric energy self-sufficiency usually has been the supposed objective at many wastewater treatment plants (WWTPs). The reason for this singular focus can be found in the fact that electricity generation at WWTPs has always been rather limited while thermal energy (heat) has often been available in excess (Kretschmer et al [3]). WWTPs have been considered more as an “energetic island” than as being part of a local energy system to date
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