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Residual heat utilization.

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Water treatment plants (WTPs) play a crucial role in providing clean and safe water to households and industries. However, WTPs consume a significant amount of energy to treat water, and this energy consumption contributes to greenhouse gas emissions and high operating costs. Therefore, it is essential to explore innovative ways to optimize the energy efficiency of WTPs and reduce their carbon footprint. One such method is Residual Heat Utilization (RHU).

RHU is the process of capturing and utilizing excess heat generated during the wastewater treatment process. This heat energy is usually lost and released into the environment. With RHU, however, the excess heat is recovered and reused for other energy needs in the plant or nearby facilities, such as heating and cooling systems or hot water production.

In many places within industry, as well as government facilities, there is waste heat, which is lost to the environment. But great things can also be done with this waste heat, so that ultimately the loss is reduced and the heat is not lost.

Why use waste heat?

Using waste heat in WTPs has several advantages. 

Reducing the overall energy consumption of the plant, leading to lower operating costs and reduced carbon emissions. 

Reducing the need for additional energy sources, such as fossil fuels, to meet the plant’s energy needs. 

Generating additional revenue by selling excess heat to neighboring buildings or industries.


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Wastewater as a heat source

One of the main sources of waste heat in WTPs is the treated wastewater itself. When water is treated, it goes through various stages such as filtration, disinfection and settling, generating heat energy. This heat energy can be recovered and reused for various purposes such as preheating inflowing water, sludge digestion and space heating.

Cogeneration systems

Another source of waste heat is the use of cogeneration systems. Cogeneration systems produce electricity and heat simultaneously, making them highly efficient. These systems use natural gas or biogas to generate electricity, which can be used in the plant or sold back to the grid. The excess heat generated during electricity generation is captured and used for RHU purposes.

The challenges and optimization of residual heat utilization

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The main challenge in implementing RHU in WTPs is the variability of the heat energy generated. The amount of heat generated depends on several factors, such as wastewater flow rate, temperature and organic content. Therefore, designing an efficient RHU system requires careful analysis of the plant’s heat generation patterns and energy requirements.

Heat exchanger

One way to optimize RHU in WTPs is to use a heat recovery unit (HRU). An HRU is a heat exchanger that captures heat energy from wastewater and transfers it to the water used for heating or cooling purposes. The HRU can be installed at various points in the treatment process, such as after the primary settling tank or the final clarifier.

Thermal storage tanks

Another way to optimize RHU in WTPs is the use of thermal storage tanks. Thermal storage tanks store excess heat energy generated during peak periods and release it during low-demand periods. This method helps maintain a stable and consistent supply of heat energy for RHU purposes.

RHU can also be integrated with other renewable energy sources, such as solar and wind power. For example, a solar thermal system can be used to preheat influent water before it enters the plant, reducing the plant’s energy consumption. Wind turbines can also be installed on the plant site to generate electricity, which can be used for RHU purposes.

An innovative way to optimize water treatment plants.

The Deployment of Inovative Technologies:


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CirTec has developed CRESCENDO for this purpose. CRESCENDO is based on the GaLiCos technology, which is a Gas Liquid COntact System. With this system, a very intensive exchange takes place between liquid and gas, allowing it to be used for various applications, such as evaporation (thickening of liquids), scrubbing of (hot) gases, stripping, cooling and a range of related purposes. 

The GaLiCos was originally manufactured entirely in stainless steel, with the CRESCENDO developed in a plastic version specifically for corrosive liquids and gases, with very high or very low pH and liquids with high salt concentration, such as brine. Because of the further developed modules, the plastic version is now favorable in construction which significantly reduces the production costs and now the plastic version is used for almost every application.

The liquid flows as a thin film over perforated plates. The flow is maintained by continuous circulation across the plates. At the same time, a horizontal gas stream is drawn through the perforations, resulting in intensive mixing and high dust transfer. This patented method provides a very intensive gas/liquid contact and offers optimum exchange of components at minimum energy input. Even “waste energy” from heating, cooling and ventilation can be put to good use.

CRESCENDO has been successfully in use for several years. When applied to thickened concentrated (wastewater) streams and to recover valuable resources, the use of low-grade residual energy saves energy and costs. Unique features: the design of the plates creates a large contact surface between gas and liquid, allowing maximum exchange between gas and liquid, and at the same time no contamination of the plate surface occurs, neither at the bottom (which remains dry) nor at the top (due to high turbulence).

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Contact us

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Are you also looking for an inovative way to optimize energy efficiency in water treatment plants? Curious about the best options and possibilities within your company? Feel free to contact us and let’s explore together in a short conversation what Cirtec can do for your company.