The Devastating Effect of Sewage Discharge on Nature

sewage discharge into nature

The term ‘wastewater’ is broadly used for everything that flows into aquifers from sewage. It includes rainfall collected from the streets, agricultural water excesses, industrial and domestic waste. Wastewater bears a number of contaminants into aquifers, some of them toxic and lethal for river life. When in water, these contaminants can do harm for both humans and entire ecosystems. For example, sewage discharge provides a favourable environment for algae colonies, which have the potential to harm or even destroy populations of river life.

Dr Anne Jungblut is the Principal Researcher in algae, fungi, and plants in the Natural History Museum in London, UK. She believes that massive algae blooms caused by sewage are ‘a big problem’. Blooms can lead to a change in biodiversity, and can impact the functioning and richness of an ecosystem. Algae has a huge impact on an ecosystem and big blooms can change the whole river.

When Sewage Meets Rivers

Obviously, there are legal regulations for untreated sewage discharge around the world. However, to prevent sewers becoming overwhelmed, water companies are allowed to release sewage into rivers in emergencies. This generally occurs in times of heavy rain to prevent the sewers backing up into buildings. Such regulations leave room for illicit action, which is, quite logically, a frequent occasion. As a result, everything there is in wastewater – domestic waste, chemicals, microplastic and more – ends up in rivers.

The United Kingdom has been struggling with wastewater treatment for the last 2 years. Following the impact on the UK’s supply chains from Brexit and the COVID-19 pandemic in 2020, the Government enabled companies to discharge sewage at any time if there is a lack of chemicals to treat it. The regulation was withdrawn earlier in 2022, but within these 2 years the quality of river waters has seen a dramatic decrease.

Algal Blooms Vs Ecosystems

Releasing sewage into rivers introduces a large amount of nutrients into the water, like nitrogen and phosphorus. Dr Anne Jungblut explains how grave the consequences of river pollution can be.

“When sewage is released into rivers, it contains a lot of nitrogen and phosphorus. These can stimulate the growth of algae, such as phytoplankton in the water or mats known as biofilms in the sediments, which can lead to algal blooms. A large amount of algae has an impact on the rest of the ecosystem, such as blocking out the light that plants need for photosynthesis. When these plants, and the algae itself, start to die, they are eaten by a lot of bacteria which reduces oxygen in the water, killing fish and other organisms,” – Dr Anne Jungblut Principal Researcher at Natural History Museum in London, UK.

This oxygen deficiency leads to reduction in population of one species, and other species, namely anaerobic ones, thrive at their expense. The conditions of the river affect which groups prosper. Slower moving rivers, or those which have become blocked, can promote the growth of toxic algae which prefer these conditions.

Another threat is toxins released into rivers. Part of them is discharged with wastewater (heavy metals, pesticides, microplastic). Another part is produced by blue green cyanobacteria blooms that follow algae blooms. According to research, fish change their behaviour under the influence of certain toxins the same way people do when consuming drugs. Fish prefer warmer wastewater discharge, and they often develop changes in their organs that prevent them from reproduction.

Restoring Rivers

Once sewage has been released into a river, there is little that can be done to prevent its impact. However, the ecosystems can recover if they are not overwhelmed.

Massive environmental catastrophes can be prevented with consistent high-quality wastewater treatment and water purification. This is why it is so vital to develop, modernise, and renovate wastewater treatment facilities around the world.

“The possibility of recovery depends on the nature of the spillage. An acute spill comes and goes, so while it might remove a lot of insects from the river, the recovery can be quicker. For instance, many freshwater insects tend to fly up the river as adults to lay their eggs, which are then washed back down. This allows recolonisation of the river to take place. However, chronic pollution causes real problems as there is no possibility for recovery,” – Steve Brooks, Researcher at Natural History Museum in London, UK.