Diluted Wastewater Still Harms Rivers

Study Highlights the Need for Intensified Efforts in the Treatment of Polluted Water to Preserve Aquatic Diversity

A study conducted by the University of the Basque Country (UPV/EHU) has emphasized the importance of increasing efforts in the treatment of polluted water to protect aquatic diversity. The study, carried out by the Stream Ecology group, utilized water from a large wastewater treatment plant to demonstrate that even when properly treated and highly diluted before discharge, this water still has an impact on river diversity and the trophic web (food web). The findings suggest that current limits and treatment procedures may not be sufficient to safeguard the natural properties of food webs.

Improvements in Water Quality, but Hidden Environmental Effects

Wastewater treatment plants have significantly enhanced water quality worldwide by reducing the amount of pollutants reaching aquatic ecosystems through environmental regulatory procedures. However, despite the treatment of effluent discharged from these plants, a complex mixture of pollutants, nutrients, and pathogens remains. The environmental effects of these substances, which may go unnoticed due to other factors, can have an impact on aquatic ecosystems. Advanced wastewater treatment plants implement additional measures to reduce nutrients, organic matter, and metals in sewage. Although these discharges are highly diluted, they can still exert minor effects if they persist over a long period of time.

An Innovative Experiment to Study the Effects

To comprehensively study the effects of wastewater treatment plants, the Stream Ecology group designed an innovative experiment that spanned several years. The researchers first measured various variables in two selected reaches of an unpolluted stream for one year to establish a baseline. This allowed them to observe how these stream variables changed over time and location. Next, properly treated and highly diluted water from a wastewater treatment plant was diverted to one of these downstream reaches. Measurements were then taken over another year in both reaches to assess the changes brought about by these discharges on stream diversity, the trophic network, and the overall functioning of the ecosystem.

Significant Effects on the Ecosystem

The study revealed that even when discharged in a highly diluted form, treated wastewater can have significant effects on the ecosystem, impacting the structure and functioning of stream communities. Although the toxicity of the effluent was found to be low, the researcher explained that invertebrate diversity decreased, communities became more heterogeneous, and there was an increase in algae and herbivory. While the wastewater is treated, certain nutrients that promote algae growth and organic matter enter the stream. Additionally, pollutants can lead to the disappearance of sensitive invertebrates and their replacement by more resistant species.

Intensified Efforts Needed for Conservation

The study highlights that advanced wastewater treatment processes currently in use still have an impact on freshwater ecosystems. To ensure the preservation of freshwater food webs, intensified efforts are required in the treatment of polluted water. Adhering to the limits set by legislation helps reduce problems, but impacts still occur. The researcher from the Stream Ecology group concluded that for optimal conservation of stream trophic networks, treatment measures need to be even more stringent.

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, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.
• SDG 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, in particular 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, in particular forests, wetlands, mountains and drylands, in line with obligations under international agreements.

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 wastewater safely treated
• Indicator for SDG 14.1: Concentration of nutrients in coastal and marine areas
• Indicator for SDG 15.1: Extent of water-related ecosystems

Table: SDGs, Targets, and Indicators

Explanation:

The article discusses the need to intensify efforts in the treatment of polluted water to preserve aquatic diversity. This issue is connected to several Sustainable Development Goals (SDGs): SDG 6 (Clean Water and Sanitation), SDG 14 (Life Below Water), and SDG 15 (Life on Land).

Based on the content of the article, specific targets under these SDGs can be identified. For SDG 6, the target is to improve water quality by reducing pollution and untreated wastewater. For SDG 14, the target is to prevent and reduce marine pollution, including nutrient pollution. For SDG 15, the target is to ensure the conservation and sustainable use of freshwater ecosystems.

The article also mentions or implies indicators that can be used to measure progress towards these targets. The indicator for SDG 6.3 is the proportion of wastewater safely treated. The indicator for SDG 14.1 is the concentration of nutrients in coastal and marine areas. The indicator for SDG 15.1 is the extent of water-related ecosystems.

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Source: newswise.com

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