When we flush the loo or pull the plug, most of us don’t give a thought to what happens next. Often, the only time we think about sewage is when something goes wrong and our noses are offended.

At Barston Sewage Treatment Works near Solihull in the West Midlands you can’t escape funny odours and the reality of raw sewage. Not only does the site process an average of 15,000 cubic metres of waste each day, it has a dedicated education centre offering free sessions to primary and secondary schools.

It’s the perfect place to study geography and science; ready-made sessions cover topics such as investigating rivers, water cycles, improving the environment, micro-organisms, and gases around us. Sessions can be organised to fit teachers’ objectives, says Malcolm Smith, the centre’s education officer. “We are adaptable and it’s not just about geography and science. Sessions often incorporate team building and citizenship and PSHE issues and we are planning an industry day.”

On a day when spring and winter fight it out over seasonal change, a Year 6 class from Somerville Primary School in Birmingham are learning all about water. After a fast-moving session in the classroom, stocked with a stash of resources to make most teachers weep, it’s time for the guided tour. It proves to be a revelation for both children and adults.

We follow a trail that takes in extraction, filtration, oxidation and clarification. It starts at the inlet flow with untreated sewage and ends at the stream where the treated water is released. On the way, we peer into skips with the extracted detritus and grit; stare in disgust at the fat vat with dirty, foaming oil that’s been skimmed from the water; nod in admiration as we discover how powerful bacteria are used to remove the harmful bacteria from sewage water and sludge (or poo to the pupils) and how the methane gas by-product is used to heat the sludge digesters.

Smiles waver slightly when it’s revealed that the harmless but nutrient-rich sludge is given away free to farmers to spread on their fields. We see pumps removing detergent bubbles, giant sprinkler systems spraying bacteria, rock-covered bacteria beds, water-sampling equipment, sedimentation tanks and sheds full of computers that monitor the site.

There’s even a net for collecting frogs that have somehow survived the journey through the sewers.

Back in the classroom (an aroma-free zone), its time for the pupils to make sewage soup - an innocuous but murky mix that includes crisp packets, loo roll, leaves, dirt, Cheerios, toothpaste and shampoo. Once they’ve mixed the goop and observed the behaviour of the ingredients, they then have to work out how to separate it, using sieves, funnels, paper towels and filtration paper.

This is a visit that fascinates children, says Malcolm Smith. “They go home and tell their parents ways of saving water and what happens with the sewage system because most people don’t know how it works. They are just amazed at how the water is cleaned without using any chemicals and how a lot of things are recycled.” And the pupil verdict: “It was fun because there were so many activities to do and I learned a lot,” says enthusiastic 11-year-old, Sameer Hussain. “We did a little bit about it at school but I was surprised at some of the funny stuff that goes in the drains.”

Barston Sewage Treatment Works is owned by Severn Trent Water and free educational sessions are also available at their other sites at Carsington in Ashbourne, Cropston in Leicester, Hayden in Cheltenham and Stoke Bardolph in Nottingham. All sessions are run by teachers on secondment.

ON THE SPOT

Jay Judge is a Year 6 teacher at Somerville Primary School in Small Heath, Birmingham

This is the third year I have come here and it gets better and more interesting. We come once a year with Year 6 - this is one of their favourite trips. We come just before SATs because the children get a lot of hands-on experience and it helps with the science test papers. The visit helps with the separating materials topic and they also do an environmental project in geography on rivers and the water cycles so they pick all that up.

They learn lots of skills from this trip and I thought the sewage soup exercise was brilliant. The kids loved the activity and it showed. I don’t think they realise the information they are getting from it. They see it as fun but they are getting the science into their heads as well. We get a pack to take back and they love doing that and we do more work from it in school.

One of the great things that they get from the trip is that they learn to look after water and how precious it is.

On the map

Name = Barston Education Centre, Barston Sewage Treatment Works, Friday Lane, Solihull B92 0HY

Tel: 01675 443079

www.stwater.co.uk