What is Wastewater Heat Recovery?

Much of the energy consumed in heating water for many different applications in domestic, commercial and industrial settings is wasted to the drainage system.

Recovery of waste heat from showers is a concept that has existed for decades with commercially available solutions [1]. However, significantly larger amounts of energy are available to be recovered in wastewater generated outside of the domestic sector. The hospitality sector in the UK was estimated to produce 1.4 TWh/yr of heat in wastewater discharges [2]. Similarly, hot-water intensive industries such as brewing and food processing have been reported to have significant wastewater heat recovery potential [1-2].

While technical solutions for Wastewater Heat Recovery (WWHR) in the domestic sector are available, these are still in development for commercial or industrial applications. Due to the more polluted nature of these wastewaters and differences in the timing between heat demand and wastewater generation, technical solutions for WWHR of this kind are more complex [1].   

References: [1]. Nagpal H, Spriet J, Murali M, McNabola A. (2021) Heat Recovery from Wastewater - A Review of Available Resources, Water, 13, (1274).

[2]. Spriet J. & McNabola A. (2019) Decentralized drain water heat recovery from commercial kitchens in the hospitality sector, Energy & Buildings, 194, p247-259.

  • In brief, using heat exchangers, heat is transferred from waste water to incoming cold freshwater. Read more in details below.

  • You can read more about two case studies of WWHR in industrial and commercial kitchen settings here.

  • If you are based in Zambia and your business could benefit from DWHR, contact us to explore the potential to reduce GHG emissions, energy use and costs.

How does it work?

The energy efficiency of such processes can be improved through the adoption of WWHR systems, as hot waste water passes through a heat exchanger and heat is transferred to incoming cold water streams or to a hot water storage system (Figure 1).

This system reduces the demand for energy to heat up incoming cold water, driving down consumption of fossil fuels and emissions of greenhouse gases, as well as reducing costs.

Application in Zambia

In REHEATZ, we are exploring the potential to widely apply the WWHR concept to different industrial processes, specially in the food and beverage sectors.

The REHEATZ solution will help Zambian food processors and other hot water intensive large companies to meet environmental, sustainability and governance commitments associated with foreign direct investment requirements to reduce their CO2 emissions, emissions of air pollution, and emissions of hot wastewater to the natural environment.

You can read more about the key steps involved here.