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Clean Isn’t Clean: How Treated Wastewater Affects Fish
AI generated symbolic image of a fish in treated wastewater that is not clean
Each time I turn on the tap to fill my bottle, I feel grateful to live in a place where clean water is readily available. I’m very aware that not everyone can get clean water this easily. Also, water pollution is in our urbanized world an issue that requires attention constantly. This is because wastewater can come from many homes, companies, and factories. This wastewater can contain all kinds of pollution and contamination, such as viruses, excess nutrients, chemicals, radioactive material, and heat.
These contaminants can have all kinds of consequences on aquatic animals, as small amounts surround them all the time. For example, in a previous article, I explained how wastewater can make fish go big. Because of the negative consequences of contaminants, wastewater treatment facilities have been built in many parts of the world.
Where I live, these facilities are common to remove pollutants and contaminants from the incoming wastewater. Unfortunately, these facilities are not always able to remove all (types of) pollutants and contaminants. For example, metals, pharmaceuticals, personal care products, detergents, and tiny plastic particles can be very challenging to remove. This means that outgoing wastewater can still contain a mixture of pollutants and contaminants.
The mixture of pollutants and contaminants is a huge concern, because of the negative impact on the environment and aquatic animals, affecting both animals’ bodies and behavior. How much and how exactly aquatic animals are affected also depends on other factors, such as temperature.
Understanding differences depending on temperature is important to see how aquatic animals are affected in different seasons and different parts of the world. Also, different temperatures can cause the impact of pollutants and contaminants to change and how well an animal’s body can deal with them.
This is how warm (20 °C / 68°F) and cold (4 °C / 39.2 °F) temperatures change the impact of treated wastewater on the physiology and behavior of fish, in particular fathead minnow, which lives across North America.
Fathead minnow (credit: “Pimephales promelas” by an officer or employee of the United States Government is published in the public domain)
1. Physiology
The physiology of fish in treated wastewater is only impacted with warm temperatures. Fishes’ physiology involves the normal functioning of their bodies and body parts.
Fathead minnows’ physiology is impacted because being exposed to warm compared to cold water causes their metabolic rate to increase about five times compared to cold water. Metabolism involves the chemical processes that happen in their bodies to stay alive. When the metabolic rate is high, this means that the chemical processes take place faster. This is the case both when they are at rest and when they are very active. When fathead minnows are also exposed to treated wastewater, their metabolic rate increases even further, about six to seven times compared to fish in cold water.
The consequence of a higher metabolic rate is that fathead minnows require more energy to stay alive and more strain is put on their organs. Also, the volume of red blood cells compared to the total volume of blood reduces. This is unhealthy because red blood cells carry oxygen to cells, which means that fewer red blood cell causes less oxygen to be available in cells. Together, these consequences reduce their overall body condition and health.
Fathead minnow (credit: “Fathead Minnow — Breeding Male” by Rankin1958 is licensed under CC BY-SA 3.0)
2. Behavior
The behavior of fish in wastewater is impacted by both warm and cold water.
With warm temperatures, fathead minnows exposed to a lot of treated wastewater become less bold: they stay longer in their refuges. This can be problematic because having a higher metabolic rate in warm water requires more energy. As a result, staying in their refuges can reduce their energy level and fitness.
With low temperatures, fathead minnows tend to spend less time with other fish in their shoal when surrounded by a lot of treated wastewater. This can be critical as being alone makes it harder to keep an eye on predators; being around other fish makes them less likely to be eaten by other fish. Also, when fish follow each other to good foraging areas, being less sociable makes it hard to find food. This is especially critical for fish exposed to wastewater in winter when food is scarce.
So, even when wastewater is treated by a treatment plant, this water impacts marine life. For example, the physiology and behavior of fathead minnows are impacted when they are surrounded by treated wastewater. Their physiology changes in warm water because chemical processes in their bodies are faster. This reduces their overall health. Also, treated wastewater makes them less bold in warm water and less sociable in cold water. Being less sociable makes it less likely that they find food and more likely that they are eaten by other fish.
Importantly, when the overall health and number of fathead minnows reduces, it indirectly also impacts us. This is because these disruptions affect the whole food web, which is also essential for our survival. That is why it is important to reduce wastewater pollution and increase wastewater quality as much as possible.
How we can take action
Here are practical ideas of what you and I can do to increase wastewater quality:
- Disposing of (toxic) substances in appropriate bins instead of flushing them through the toilet or drain
- Taking as few medicines as possible and disposing of them correctly to reduce pharmaceutical pollution (further reading: How Pharmaceutical Pollution Harms Aquatic Organisms)
- Using natural instead of chemical cleaning products
- Using as little as possible when using personal care products, such as sunscreen (further reading: Beware: Our Sunscreen Can Affect And Kill Marine Animals)
Which one of these can you implement in your daily life? And do you have further ideas of what you and I could do? Thank you in advance for putting them into practice and sharing them in a comment to this question to inspire all of us.
Did you enjoy this article? Then I’m sure you’ll love my book “A Guide to A Healthier Planet” as well:
A Guide to a Healthier Planet
This book focuses on closing the gap between scientific insights on pressing environmental issues that do not often reach the general public.
https://www.sustainabledecisions.eu/guide-to-a-healthier-planet
About the author
Dr. Erlijn van Genuchten is a an internationally recognized environmental sustainability expert. She is a science communicator, helping scientists in the fields of nature and sustainability increase the outreach of their results and allowing us all to put scientific insights into practice and contribute to a sustainable future. Erlijn has inspired thousands of people around the world — for example — by supporting the United Nations with her expertise, her book “A Guide to A Healthier Planet” published by Springer Nature, her YouTube channel Xplore Nature, and her posts on social media.
Credit
This article is based on: Mehdi, H. (2022). Impacts of wastewater on aquatic biota in summer and winter (Doctoral dissertation).
Fathead minnow illustration:
Author: officer or employee of the United States Government is published in the public domain)
Fathead minnow picture:
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4 w
Humans and in particular leaders of institutions, organizations,companies, factories and plants need to rethink twice and embrace sustainable living where protection of life on the planet plays a center role.
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4 w
This is a vital reminder! While we often take clean water for granted, it's crucial to address how treated wastewater impacts our ecosystems and ensure safe, clean water for all.
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4 w
We can protect these fish by taking the right actions on our water systems