Wastewater Boosts River Methane Emissions, New Study Finds

A recent study has found that a section of river receiving treated wastewater releases five times more methane than a section without it. This research was conducted by Ida Peterse and Lisanne Hendriks from Radboud University and was published in the journal Science of The Total Environment.

The scientists measured methane emissions along parts of the Linge and Kromme Rijn rivers. According to Peterse, they used a floating chamber to capture the gases rising from the river's surface for analysis. They also examined the nutrients present in both the water and soil. The team measured methane levels at several locations: 500 meters before the water treatment plant, right at the discharge point, and at intervals up to two kilometers downstream. Their results revealed that methane emissions peaked two kilometers after the discharge point, where they were five times higher than at the point of discharge itself.

The research highlights the impact of treated water on rivers, even if the water meets Dutch cleanliness standards. According to Hendriks, the treated water contains nutrients such as nitrogen, phosphates, and carbon, which promote the growth of algae. When these algae die and sink to the riverbed, they create a favorable environment for methane-producing microorganisms. As the process takes time, the increase in methane emissions becomes more noticeable further downstream from the discharge point.

Peterse emphasized that while the water meets the country's quality standards, it still contributes to higher methane emissions, which is concerning given that rivers are responsible for about 50% of methane emissions globally. This research suggests that addressing this issue could be crucial in reducing methane output from water systems.