Democratizing Wastewater Treatment: The Role of Passive Ecosystem Services Compared to Engineered Processes

Human activities have a significant impact on natural waters, aquatic biodiversity and the quality of drinking water resources. For Professor Mathieu Lapointe of the Department of Building Engineering at the École Superior de Technology (Éts), it is possible to treat certain types of wastewater – currently untreated – globally using more sustainable and affordable methods on site.

In a study conducted by Professor Lapointe and published in Nature waterThe rate at which certain types of untreated water are discharged into the environment — urban and rural runoff, as well as those from industry — varies from country to country. Low-income countries tend to dump more than high-income ones. More specifically, wastewater treatment rates can vary from 4% to 95%, depending on the country.

Water treatment plants are not only expensive, but also consume a lot of energy. Moreover, it does not solve problems associated with urban waterproofing or irregular excess precipitation caused by climate change. In addition, agricultural and urban runoff is often considered insufficiently polluting to justify the cost of using conventional treatment plants. As a result, runoff remains untreated even though it can pollute aquatic ecosystems.

Professor Lapointe recommends passive, modular, inexpensive and decentralized solutions that are able to retain some pollutants. These include bio-warming cells, aggregate casting systems, and seepage zones through functional soils. It also suggests a greater reliance on “negative ecosystem services,” including microorganisms, oxidation, photodegradation, and inactivation, to name a few.

“To treat water that is not currently treated for technical-economic reasons, such as stormwater runoff, it is preferable for government authorities and environmental organizations to promote passive systems, which can be integrated or combined with more traditional wastewater collection and treatment processes.”

Although more in-depth studies are needed to better assess the benefits and cost benefits of this solution that combines passive technology and methods, Professor Lapointe is optimistic about the feasibility of this alternative.