Even Treated Sewage Harms Freshwater Ecosystems – Eos
Even Treated Sewage Harms Freshwater Ecosystems Eos
Rivers and Wastewater: Impacts on Freshwater Ecosystems
Rivers are awash with excess nutrients, chemicals, and other pollutants, including sewage. Globally, roughly 50% of wastewater is treated at facilities before being released into nearby bodies of water. But new research shows that even advanced treatment might not be enough to safeguard the health of freshwater ecosystems.
Researchers released dilute, treated wastewater into an unpolluted stream in northern Spain and made a before and after comparison of energy flows through the ecosystem.
“We found subtle yet fundamental shifts in ecosystem function after adding wastewater,” said Ioar de Guzman, a freshwater ecologist at the University of the Basque Country in Spain and lead author of the study. By manipulating a pristine ecosystem, she and her colleagues could isolate the effects of wastewater, which can be masked in streams that contain other types of water pollution.
Impact of Wastewater Pollution
Agricultural runoff, containing nitrogen-rich fertilizer, is a familiar blight, causing lurid green algal blooms that choke aquatic life. However, wastewater is probably a bigger stressor to river functioning than agriculture, according to Mario Brauns, a freshwater ecologist from the Helmholtz Centre for Environmental Research in Germany.
Besides nitrogen and other nutrients, sewage is laced with an insidious cocktail of toxic contaminants derived from cleaning and beauty products, pharmaceuticals, and more.
Challenges in Wastewater Treatment
Decades of investment to reduce wastewater pollution have shown that treatment can significantly improve water quality. However, even after advanced treatment, toxic compounds and nutrients still remain, highlighting the need for further improvements.
In their experiment, de Guzman and colleagues used wastewater from a large treatment facility near Elgoibar, northern Spain, which employs physical and biological processing, involving separation tanks and microbial digestion, for example, and advanced screening to remove extra nutrients and metals.
Assessing Ecosystem Health
The researchers conducted ecological impact assessments by studying an unpolluted stream in good ecological condition. They measured the amount of leaf litter and biofilm, counted and measured invertebrates, and studied the fish population. They then introduced wastewater into only the downstream reach of the stream and repeated the assessments.
Energy Flows in the Food Web
The team quantified the amount of energy produced and consumed at different tiers of the feeding network to understand ecosystem health. They found that the introduction of wastewater led to changes in the invertebrate community and a decrease in energy flowing to the fish population.
The study highlights the need for continued efforts to improve wastewater treatment. Diffuse inputs of pollution from agricultural land and roads can amplify the overall effect on water quality. Understanding how these combined stressors impact ecosystem function is crucial.
Even treated sewage can harm freshwater ecosystems, as shown by this study. The findings emphasize the importance of sustainable development goals (SDGs) related to water quality and ecosystem health. Further research is needed to develop effective strategies for reducing wastewater pollution and protecting freshwater ecosystems.
SDGs, Targets, and Indicators
1. Which SDGs are addressed or connected to the issues highlighted in the article?
- SDG 6: Clean Water and Sanitation
- SDG 14: Life Below Water
- SDG 15: Life on Land
2. What specific targets under those SDGs can be identified based on the article’s content?
- SDG 6.3: By 2030, improve water quality by reducing pollution, eliminating dumping, and minimizing release of hazardous chemicals and materials.
- SDG 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, particularly from land-based activities, including marine debris and nutrient pollution.
- SDG 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services.
3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?
- Indicator for SDG 6.3: Proportion of bodies of water with good ambient water quality
- Indicator for SDG 14.1: Concentration of nutrients in coastal and marine ecosystems
- Indicator for SDG 15.1: Extent of freshwater ecosystem degradation
Table: SDGs, Targets, and Indicators
|SDG 6: Clean Water and Sanitation||6.3: By 2030, improve water quality by reducing pollution, eliminating dumping, and minimizing release of hazardous chemicals and materials.||Proportion of bodies of water with good ambient water quality|
|SDG 14: Life Below Water||14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, particularly from land-based activities, including marine debris and nutrient pollution.||Concentration of nutrients in coastal and marine ecosystems|
|SDG 15: Life on Land||15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services.||Extent of freshwater ecosystem degradation|
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