Where does our sewage go?

From the moment you flush the toilet or pull the plug in the sink, follow the journey of wastewater

(Image credit: Michal Jarmoluk/ Pixabay)

In countries where water is readily available to us, we can sometimes take it for granted. It has so many uses, either personally in our own homes, as part of most industrial processes or in agriculture to help us grow our food. However, once we have utilised this water, it becomes contaminated and can be a danger to our health. What do we do with the water then?

Most wastewater follows the same route as it is directed underground and into treatment plants. Having learned from previous issues throughout history, we know that dumping sewage back into rivers and oceans untreated has dire consequences for everyone’s health. 

Sewage systems are tasked with the job of removing debris, from large plastic objects that have found their way into drains to smaller mineral particles such as grit or stones. Once contaminant-free, the water is returned to nature to repeat the cycle.

Click to enlarge (Illustration by Adrian Mann/ Future PLC)

Early methods

Today’s approach to managing and reusing wastewater seems an efficient one, especially when compared to past methods. In fact, during the Middle Ages there didn’t really seem to be many methods in place at all. Cesspools were often used for sewage – or households would simply pour their wastewater into gutters and let the rain dictate its path down the drain.

This demonstrates the importance of today’s systems, as disposing of wastewater this way resulted in diseases such as cholera and became a serious threat to public health and hygiene. Following this, it was decided that waste should be transported away from living areas and released straight into lakes. Without any purification process, this led to a growing water-pollution problem.


This article was originally published in How It Works issue 136, written by Ailsa Harvey


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