Flush it away?

Activity overview

Run the activity

1. You’re going to watch a short video. The aim isn't to find right answers, it's to explore ideas and find out what they know.

• Do they know what might happen based on the image?

2. After you've watched the video, ask the children what they think the point of the experiment might be. Check that they understand that it is showing which things should and shouldn’t be flushed down the toilet. Lead a discussion with your class:

•   Have you ever flushed any of these things down the toilet? 
•   What did you notice happened to each material?
•   Which things would break up when flushed down the toilet? Which things would not break up?
•   Why is it important that only things that break up are flushed down the toilet?

3. Ask the class to describe what they saw using only one word

Background science

All the wastewater from our toilets, taps and showers leaves our houses in pipes to be recycled. The pipes take our wastewater underground to the bigger pipes and tunnels of the sewers. Including the rainwater which also drains into the sewers, there are over 11 billion litres of wastewater produced every day in the UK. Wastewater is dirty and needs to be treated at a wastewater treatment works by going through the following stages:

1.    Screening: the wastewater passes through a sieve which removes large items that have not broken down in the sewers. 
2.    Settlement tanks: the poo falls to the bottom of the tanks and is pumped away for further treatment.
3.    Aerated tanks or trickling filters: Air is supplied so that useful bacteria multiply and they feed on the tiny bits of poo that are left in the wastewater.
4.    Settlement tanks: the useful bacteria sink to the bottom of the tanks and are removed.
5.    The clean water can then be released into rivers or seas and join the water cycle again. 

Without being recycled like this, the wastewater would pollute our rivers and seas and kill much of the wildlife living there.

We need to be careful about what we put into our sewers, otherwise they get blocked up and this can cause sewage spills. Only toilet paper, pee and poo should be flushed down our toilets and we should not put cooking oils and fats down the plug. When fats, oils and grease mix with wet wipes and other flushed products that don’t break down, the result is a hard rock-like solid called a fatberg. Fatbergs clog up the sewers and are very difficult to remove.

Watch out for

Some people think the word ‘flushable’ means that an object fits down the toilet and so will flush away. This does not consider what happens next.

The people who look after the sewers would like us to only say something is ‘flushable’ if it breaks down easily, is biodegradable and does not block up the sewers.

Take it further

Activities

After watching the film, ask children if they have any questons about what should and shouldn’t be flushed down the toilet. Do they think that all brands of toilet paper would flush away, including those made from recycled materials? Do they think that some types of tissue might break up better than the one in the film? Are there other items that they would like to test to see if they would flush away? Perhaps cotton wool, kitchen towel or even sweet wrappers?

Using the technique shown in the film, children could design a comparative test to find out which items are flushable. They could consider which variables they are going to keep the same.

Children could promote the 3P’s (toilet paper, pee and poo) message by creating posters to explain why only toilet paper, pee and poo should be flushed down the toilet.

Many people around the world do not have a flushable toilet because there is no sewer system. Older children (aged 9-11) could learn about how scientists are trying to help people who have little access to water and electricity. A waterless toilet has been designed and made which safely recycles poo and pee without flushing it away. The Bill and Melinda Gates Foundation are planning to produce waterless toilets at a larger scale. For more details and a teacher guide, you can download the Primary Science Teaching Trust’s resources here.

Linked Explorify activities- our recommendations:

Wastewater needs to be treated to protect the River life. Explore other watery habitats with Wet, wet, wet.

Watch

Follow Brian Cox as he explores a sewage treatment works in this BBC film. For a more detailed explanation of the journey of dirty water, watch this episode of Curious Cat.

Newsround has fatberg footage and facts here and investigates why sewage spills are increasing in the article and videos here. In this episode, the Go Jetters tackle a fatberg.