The Science of Sewers

As Year 7 filed into the hall for a special presentation by Severn Trent Water they were surprised to see an inflatable toilet and bath on the stage as well as a mock-up drain and various pipes.  Presenting the event was Sharan Gill who was keen to get started on her topic of water, especially wastewater!

Photo by Giorgio Trovato on

The hour-long session began with a quick overview of the history of Severn Trent Water and about the large community the company serves.  From there, students were shown how wastewater is collected and transferred from toilets and sinks and on to the sewage treatment plants though pipes and drains.  Sharan had examples of water pipes with her, referring to them throughout the presentation.  Students learnt that it takes Severn Trent Water 24 hours to treat their dirty toilet and bath water and reintroduce it cleaned back into the surrounding natural waterways.  During a clip of a sewage treatment plant there were many moans, groans and cries of, “Urgh, that’s gross!” from the audience.

Certified ‘Fine to Flush’ logo

The topic turned to what should and should not be flushed down the toilet.  There followed a question-and-answer session as suggestions were made of what was safe to flush.  As a helpful guide, Sharon advised using the Severn Trent 3Ps Rule: “Pee, Poo and (toilet) Paper” to prevent blockages and that anything natural and human is safe.  One student questioned if flushable wipes were OK to flush as they are not natural.  Sharan was impressed with this question and explained the difference between wipes labelled as ‘flushable toilet wipes’ and those marked as ‘fine to flush’.  Most wipes labelled ‘Flushable Toilet Wipes’ contain plastic and are not suitable for flushing.  ‘Fine to flush wipes are certified 100% biodegradable and contain no plastic and can be flushed.  Students were told to look out for the special logo if they wish to use wipes. “Anything that does not dissolve within five minutes should not go down the loo,” said Sharan.

One highlight of the assembly was when student George was invited to the school stage, where there was a huge, inflatable toilet, sink and pipe system.  George was asked to put his hand into the pipe system to unblock the pipe.  He pulled out a half a kilo of fat from the pipe – it was fake or course, but it certainly looked and wobbled like the real thing.  With an explanation that fat, oil and grease (FOG) was largely responsible for this, the presenter said: “When oil is in the house, it’s warm and liquid but underground and in the cold pipes and cold water it turns solid and blocks pipes.  It can clog together into very large fatbergs.  Oils and fats must go in the bin.”

Unfortunately, this embarrassed Miss Lancaster as she realised that she had been doing it wrong all these years.  “I knew I shouldn’t put oil down the sink as it could solidify, but I’ve never really known what to do with it so did anyway!  I know now that it must go into the bin once it has cooled.”

Sharan finished the session by discussing possible water industry career options with students, everything from engineering, customer support, planning, education teams and much more.

Miss Lancaster said: “What an excellent opportunity for our students to have a hands-on learning experience, outside of the classroom, with links to topics in geography and science that the students have been studying and encouraging them to think about their local and school environment.  We are very grateful to Sharan from Severn Trent Water, for visiting us”.