Abstract
The EU Directive 2018/2001 recognized wastewater as a renewable heat source. Wastewater from domestic, industrial and commercial developments maintains considerable amounts of thermal energy after discharging into the sewer system. It is possible to recover this heat by using technologies like heat exchangers and heat pumps; and to reuse it to satisfy heating demands. This paper presents a review of the literature on wastewater heat recovery (WWHR) and its potential at different scales within the sewer system, including the component level, building level, sewer pipe network level, and wastewater treatment plant (WWTP) level. A systematic review is provided of the benefits and challenges of WWHR across each of these levels taking into consideration technical, economic and environmental aspects. This study analyzes important attributes of WWHR such as temperature and flow dynamics of the sewer system, impacts of WWHR on the environment, and legal regulations involved. Existing gaps in the WWHR field are also identified. It is concluded that WWHR has a significant potential to supply clean energy at a scale ranging from buildings to large communities and districts. Further attention to WWHR is needed from the research community, policymakers and other stakeholders to realize the full potential of this valuable renewable heat source.
Highlights
The European Union (EU) has established a target to achieve a 40% reduction in greenhouse gas (GHG) emissions, and the renewable energy share of the union should be increased to 32% of total energy generation [1]
This paper presents a comprehensive review of the literature on wastewater heat recovery (WWHR) at different points along the sewer system, from user discharge to water treatment
In identifying the sources for the literature review, an initial search with Google Scholar search system was performed to understand the available literature with the following keywords—wastewater heat recovery, drain water heat recovery, and wastewater source heat pump
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Under the regulation on the governance of the energy union and climate action (EU/2018/1999), EU member states have established a 10-year integrated national energy and climate plan (NECP) [2] Under these circumstances, renewable sources of energy have been of great interest in recent years. A synthesis of the potential of heat recovery across the sewer system’s entire water cycle, from leaving the drain of a building to discharge into water bodies after treatment, is missing. Such a synthesis would be essential to present the complete picture of energy availability in wastewater in the sewer system and the advantages, disadvantages, and challenges of its exploitation in different locations, given its recent recognition as an essential renewable heat source. The work emphasizes the research gaps in the field and suggests possible avenues for future research
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