Abstract
To achieve technically-feasible and socially-desirable sustainable management of urban areas, new paradigms have been developed to enhance the sustainability of water and its resources in modern cities. Wastewater is no longer seen as a wasted resource, but rather, as a mining ground from which to obtain valuable chemicals and energy; for example, heat energy, which is often neglected, can be recovered from wastewater for different purposes. In this work, we analyze the design and application of energy recovery from wastewater for heating and cooling a building in Brno (Czech Republic) by means of heat exchangers and pumps. The temperature and the flow rate of the wastewater flowing in a sewer located in the proximity of the building were monitored for a one-year period, and the energy requirement for the building was calculated as 957 MWh per year. Two options were evaluated: heating and cooling using a conventional system (connected to the local grid), and heat recovery from wastewater using heat exchangers and coupled heat pumps. The analysis of the scenarios suggested that the solution based on heat recovery from wastewater was more feasible, showing a 59% decrease in energy consumption compared to the conventional solution (respectively, 259,151 kWh and 620,475 kWh per year). The impact of heat recovery from wastewater on the kinetics of the wastewater resource recovery facility was evaluated, showing a negligible impact in both summer (increase of 0.045 °C) and winter conditions (decrease of 0.056 °C).
Highlights
The nexus between water and energy is becoming ever more crucial in the development of innovative solutions to achieve technically-feasible and socially-desirable sustainable management for the growth and resilience of urban areas [1]
The latter is appealing in the framework of water–energy sustainable urban development; in particular, the heat energy recovery potential from wastewater could possibly be even higher than its recoverable chemical energy potential [14,15], and it does not require biological treatment to be converted into a directly usable form
Temperatures of civil wastewater may be more than 25–27 ◦C in domestic outflows [18], representing a significant thermal energy source [16]; at the inlet of water treatment plants or water resource recovery facilities (WRRFs), the temperature is far lower (15–25 ◦C or lower, depending on the climate) [16,19,20], and its use for heat recovery may be less practical
Summary
The nexus between water and energy is becoming ever more crucial in the development of innovative solutions to achieve technically-feasible and socially-desirable sustainable management for the growth and resilience of urban areas [1]. Sewage can be considered a source of different types of energy: electrical energy from bioelectrochemical wastewater treatment processes [7,8], low-head hydroelectric energy [9], biogas from anaerobic digestion [10], renewable fuels from residual sludge processing [11,12], and heat energy [13] The latter is appealing in the framework of water–energy sustainable urban development; in particular, the heat energy recovery potential from wastewater could possibly be even higher than its recoverable chemical energy potential [14,15], and it does not require biological treatment to be converted into a directly usable form. To the best of the authors’ knowledge, this is the first example of planned heat energy recovery from sewage in this European country
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