Thursday, January 18, 2024
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Recovering and regenerating water is one of the great challenges of the 21st century. This natural proposal uses plants to reuse wastewater.
Source: Colpisa
Flushing the toilet, washing the dishes, cleaning your car. For all these activities - and so many others - water takes care of the dirty work, and then it disappears. What happens to it afterwards is hidden from our sight, but recovering it is a fundamental part of maintaining the balance of water use. And plants could play an important role in that process. They could become the ones in charge of recovering wastewater.
Íñigo Elorduy, Head of BioNova Spain, is already putting this idea into motion. They use a variety of native plants to create a route where the water is recovered. This means that instead of sending wastewater to a septic tank, cesspool, or sewer system, it’s directed to a natural system with multiple stages that filters and regenerates it. "The plants purify the water," he stated. In reality, this isn't all that surprising, as plants have always been doing these processes naturally. Some are good at 'eating' metals, others at eating chemicals, and so on.
Depending on the complexity of the system, the end-product water is suitable for different uses, from using it in reforestation processes to send it back into the water cycle - and thus to aquifers - to irrigating crops intended for human consumption. Though it’s true that you wouldn’t be able to drink it directly, nowadays people also don't drink river water without first treating it with chlorine. And with just the most basic level of purification, sufficient water quality is achieved to allow it to be poured back into the river without contaminating it.
They’re also working with plants in their research on the water cycle at the CETIM Technological Center as part of their NICE project. "The objective would be to treat these types of water with nature-based solutions," explained Cristina Martínez, Head of ECO BIO Technologies. This doesn't mean that the same types of tools are used for all types of water. Each natural solution has its own use and potential, but all of them can change the way this resource is managed at the city level.
One example the expert pointed to are green walls - those vertical gardens that have begun to spring up in some cities - and green roofs that manage rainwater and allow it to be used for other purposes in the building. Rain gardens are also capable of preventing runoff caused by rain. And there are other systems that help regenerate water, such as hybrid wetlands and underground systems, which is where wastewater comes in. The key is to know what you need, what end-product water quality will be managed, and how plants in that area can help. As such, "applying these systems and improving the water cycle means going above and beyond."
Because, in the end, all these plants that have become wastewater engineers are not only managing to 'clean' water. The potential added value they offer is also critically important.
They’re "green solutions" that play a very powerful role in mitigating the effects of climate change, said Martínez. In cities, they help reduce floods (one of the effects of the climate emergency are torrential rains), something that 20th-century urban planning didn’t leave cities well prepared for. "Cities are very waterproof," she pointed out.
In addition, they can be beneficial for society. "Nature-based solutions have value beyond treating water," she added. Instead of presenting the public with a gray concrete jungle, they encounter a garden or a wetland, an area that is, in the end, nature. Given how much talk there is nowadays about greening cities, this is a considerable advantage.
It’s an added benefit that also matters when these solutions are created outside of urban environments. In fact, Elorduy highlights that what’s being created in the end is an aquatic ecosystem - "which is what the 2030 Agenda is asking for" - with all that this entails. When a more complex water purification process is carried out, the water ends up in a lake. "Nature is extremely grateful," he affirmed. "I never bring dragonflies or frogs to any of these places. They appear on their own," he stated as an example. Not only do animals and plants enjoy it, but people do too. Suddenly, wastewater becomes a paradise, opening the door to new experiences.
Recent concerns over water stress are also sparking increasing interest in green tools, which already comply by their very nature with the philosophy of the circular economy. From investment plans to legal proposals, Europe is already promoting these types of solutions. "We’re fighting over water use when we could reuse the water we already have two times over," Elorduy said.
But plants have their limitations. Martínez pointed out that there are issues when it comes to space - to be recovered, water needs to go through a route, and the plants need space to work. Elorduy added that the process takes time. Plants need some leeway to do their tasks. And then there’s the question of how much water you need to regenerate, of course. Wastewater generated by a megacity would be difficult to completely purify with one of these systems.
But that doesn’t take away from the fact that they have potential, and very intriguing, uses. Martínez acknowledged that a "change of mentality” is needed but asserted that there’s already interest in these tools, and they’re already being put into practical use. The expert pointed to the case of a Galician winery, which needed to filter the wastewater generated during the process of making wine before releasing it back into the river. A nature-based system was able to carry out that recovery. Elorduy has already installed them privately in single-family homes - managing that amount of water is "very easy," he assured - and in rural businesses. A rural hotel in Galicia has just created one of these routes, and at an organic farm in Toledo, all the water from the farm is reused thanks to these systems.
The NICE project has already worked on laboratory prototypes and is now going to launch pilots in different locations. They’re spread out all over Spain, with some locations in Europe, Egypt, and Colombia as well. And they’re working with different problems, sizes, and contexts, which is essential when testing a new tool. In this way, they’ll work in Madrid, Terrassa, Vigo, and Algeciras, among others, creating rain gardens, wetlands for treating wastewater, and green roofs.
Returning to the topic of using plants for water purification in a more general sense, there’s a lot of potential for creating wastewater treatment plants in low-population or sparsely populated areas, where the cost of a traditional treatment plant is now very high. Systems that use plants consume very little energy and can even manage sewage. In countries like Germany or Austria, Elorduy indicated, this has been done for years. Plants are what keep the water in Tokyo Bay clean.
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