Expansion of Sewer, Water and District Heating Networks in Cold Climate Regions: An Integrated Sustainability Assessment

This study presents an integrated sustainability assessment of technical alternatives for water and heating services provision in suburban areas affected by a cold climate. Each alternative combines a drinking water supply, sewerage (gravity or low-pressure), pipe freeze protection (deep burial or shallow burial with heat tracing) and heating solution (district heating or geothermal heat pumps). An innovative freeze protection option was considered, in which low-temperature district heating (LTDH) is used to heat trace shallow sewer and water pipes. First, the performance of each alternative regarding seven sustainability criteria was evaluated on a projected residential area in Sweden using a systems analysis approach. A multi-criteria method was then applied to propose a sustainability ranking of the alternatives based on a set of weights obtained from local stakeholders. The alternative with a deep buried gravity sewer and geothermal heat pumps was found to have the highest sustainability score in the case study. In the sensitivity analysis, the integrated trench solution with a gravity sewer, innovative heat tracing and LTDH was found to potentially top the sustainability ranking if geothermal energy was used as the district heating source, or if the weight of the cost criterion increased from 24% to 64%. The study highlights the need for integrated decision-making between different utility providers as an integrated solution can represent sustainability gains.