As Severn Trent marks its 50th anniversary, the company has been looking back at some of its major engineering innovations.

At the turn of the century, with the millennium bug the hottest topic of conversation, Severn Trent was investigating a different type of ‘bug’ – one that would transform the way it treated wastewater from customers.

The company scoured the world for new methods of waste treatment, which eventually led them to South Africa and a novel, biological way to remove phosphorus from wastewater.

Biological nutrient removal – known as BNR – essentially uses bugs to ‘eat’ phosphorus. Too much phosphorus in rivers can lead to algae blooms that suck oxygen out of the water – and removing it allows fish and other wildlife to thrive.

Thanks to this fact-finding mission in the 90’s, Severn Trent is now regarded as a leader in phosphorous removal, and built the very first treatment works fully focused on BNR, which is now used across many of its sites.

Peter Vale, Circular Economy Architect at Severn Trent, said: “Innovation has always been at the centre of what we do, looking for new and better ways to do things, embracing new technology.

“As we’re the only solely in-land water and waste company we have tight phosphorus permits, so we’re seen as one of the leading companies when it comes to phosphorus removal.

“You can remove phosphorus in two ways. By using chemicals or designing a treatment process to encourage certain bacteria to remove phosphorus for you.

“There were lots of new innovations coming from South Africa where a lot of new technology was being developed. We thought it would be a much more sustainable way of treating wastewater as it saves chemical use.

“It would also mean a lower cost to build sewage treatment works if we adopted this method of treatment.

“Another huge benefit of this new method was that it would keep operating costs low, which in turn would keep things such as customer bills low.”

Having spotted the potential of this new ‘different’ type of engineering, Severn Trent ran pilot trials at its Milcote Sewage Treatment Works in Stratford upon Avon, along with Derby Sewage Treatment Works.

Towards the end of the ‘90s, the company decided to build its first treatment plant at Derby dedicated to BNR, which they believe was a first in the UK. The process was then rolled out across many of its treatment works.

Today, nearly half of the wastewater that comes through its works is treated using this method.

Peter, who was in charge of some of the trials when he joined the company in 2002, added: “It shows the importance of learning from others and being open to innovation and new engineering methods – not being constrained by current thinking. We now think of it as a standard process.

“Scouring the world for this new method has meant using less chemicals today which also results in lower bills and is good news for everyone.”