Modelling temperature dynamics in sewer systems – comparing mechanistic and conceptual modelling approaches

Abstract

The vast majority of the energy consumed for urban water services is used to heat tap water. Heat recovery from wastewater is consequently an area of rapidly growing concern, both in research and by commercial interest, promoting the path towards a circular economy. To facilitate a system-wide evaluation of heat recovery from wastewater, this paper compares two one-dimensional models (mechanistic and conceptual) that can describe wastewater temperature dynamics in sewer pipe systems. The models are applied to successfully predict downstream wastewater temperature for sewer stretches in two Swedish cities (Linköping & Malmö). The root mean squared errors for the mechanistic model (Linköping Dataset1 – 0.33 °C; Linköping Dataset2 – 0.28 °C; Malmö – 0.40 °C) and the conceptual model (Linköping Dataset1 – 0.32 °C; Linköping Dataset2 – 0.20 °C; Malmö – 0.44 °C) indicate that both models have similar predictive capabilities, encouraging the use of conceptual models to reduce data requirements and model calibration efforts. Both models are freely distributed and can be easily integrated with wastewater generation and treatment models to facilitate system-wide wastewater temperature dynamics analysis.

Opportunities and Challenges for Research on Heat Recovery from Wastewater: Bibliometric and Strategic Analyses

“…The lower source of energy in heat pumps can be both wastewater from individual systems [77] and those from extensive communal systems [131,132]. In the latter case, wastewater is discharged Wastewater heat recovery technology using heat pumps is successfully applied in Scandinavian countries as well [125]. Even in less developed countries, the first investments are currently being made to recover deposited heat energy from wastewater.…”

“…Wanner et al [19] demonstrated that reducing the temperature of raw wastewater by just 1 • C can lead to a 10% increase in the required capacity of the nitrification chamber. Hence, each investment in a raw wastewater heat recovery installation requires an individual approach and detailed analysis, for example, using dedicated computer simulation software [125]. In some cases, the optimal solution may involve only slight cooling of the wastewater, while in other circumstances, the construction of a bypass may be necessary.…”