For cities worldwide, wastewater represents a significant problem that must be properly managed. Wastewater treatment plants are implemented to remove pollutants before releasing the treated water back into the environment.
However, for some years now, methods and technologies have been explored that not only seek to purify water, but also to convert waste into energy , taking advantage of the energy potential that these waters contain.
What is wastewater?
Wastewater is water that has been used for domestic, industrial , or agricultural activities and contains waste and pollutants. This water is classified as domestic, industrial, and stormwater, depending on its origin. Collectively, it represents a significant environmental problem due to the pollutants it contains and its impact on the environment if not properly treated. For cities, wastewater treatment is crucial, but in addition to cleaning it, there is potential to generate energy from it.
Energy generation from wastewater
In recent years, technology has advanced significantly, allowing wastewater not only to be treated but also to be used to produce energy. Among the most popular methods for generating energy from this waste are:
- Obtaining biogas from the decomposition of organic matter present in wastewater.
- Generation electricity by means of microbial fuel cells.
- Thermal utilization from the heat of waste water for air conditioning.
- Production of hydrogen, a clean source of energy.
Utilization of biogas
One of the most common methods is the production of biogas from wastewater. This biogas is obtained through a process called methanization , in which the organic matter present in the wastewater decomposes in an oxygen-free (anaerobic) environment.
The main product of this decomposition is methane, which can be used as an energy source for various purposes, including electricity generation and heating.
Methane has several uses, including electricity generation by burning it in turbines or heating buildings. In several cities, such as Grenoble and Strasbourg , biogas has been successfully injected into the natural gas distribution network, providing energy to both homes and vehicles.
international experiences
There are several cities and countries in the world where wastewater is already being used to generate energy. Some examples are:
- En Basel, Switzerland, heat is recovered from wastewater for heating after the purification process. It is an example of how water treatment can also be a source of thermal energy used by the community.
- In the United StatesIn Oregon in particular, the Tri-City Water Recovery Plant has implemented a system in which methane produced by the decomposition of organic matter in wastewater is used to generate electrical and thermal energy.
- En SlovakiaProjects have also been developed for the use of wastewater in the generation of biogas.
Hydrogen production from wastewater
Another innovative method that has been the subject of research is the production of green hydrogen from wastewater. This hydrogen is generated from microbial electrolysis cells, a technology that allows for the production of high-purity hydrogen using specialized bacteria that break down the organic matter present in the water. Companies like Ingeobras are developing technologies that offer this efficient and sustainable solution.
Green hydrogen has significant potential as a clean fuel, and its production from wastewater offers a more economical and sustainable approach compared to traditional hydrogen production methods such as reforming fossil materials or conventional electrolysis. As this technology advances, it could become a key solution for decarbonizing transport and the energy industry.
Electricity generation using microorganisms
Another innovative method for harnessing wastewater is the use of microbial fuel cells . This method utilizes bacteria that metabolize the organic matter in wastewater and release electrons in the process. These electrons can be captured to directly generate electricity. Microbial fuel cells are already being used in some pilot projects and have the potential to produce electricity continuously and sustainably. Furthermore, this process can improve the energy efficiency of treatment plants by reducing the need for costly aeration and pumping systems.
Success stories in cities around the world
A number of successful projects have been developed in cities around the world. For example:
- En Strasbourg, it is expected to produce 1,6 million cubic meters of biomethane daily from wastewater treatment, enough to supply energy to around 5.000 homes.
- En Helsinki, FinlandThe heating and cooling plant at Katri Vala Park uses wastewater as a source of thermal energy.
- En MadridThe Wastewater Treatment Plant (EDAR Sur) has installed turbines to harness the kinetic energy of the water at its exit and produce electricity for the plant's own consumption.
Importance of continuing to develop this technology
Although numerous projects are already underway, continued investment in research and development is crucial to improve the efficiency and reduce the costs of these technologies. Wastewater is not only a source of pollution but also represents an opportunity to generate green energy , reduce the carbon footprint, and move toward a more sustainable energy model. Larger-scale implementation of these technologies can help cities become more energy self-sufficient and generate positive impacts in the fight against climate change. Improving wastewater utilization could provide a key solution for the global energy transition.