Tony Baines is peering through an open manhole with the neutral expression of a man who is used to watching — and smelling — human waste float by. But he’s not looking at the raw sewage surging through a 2m-wide pipe beneath his feet. His focus is the strange new devices bolted near the top of the manhole, pointing down at the murk.
“Those are our new data sensors,” says Baines, a Geordie former shipyard’s draughtsman who is now the wastewater treatment manager at Northumbrian Water. “We’ve got 750 of these units, providing levels in real time.”
The sensors bounce ultrasound waves off the sewage to measure how much is flowing through the pipes in a trial section of Northumbrian’s network, which includes almost 20,000 miles of sewers serving 2.7 million customers across the northeast of England. They feed the data to computers on the ground. In this rural location, near the seaside town of Whitley Bay, the computers sit in a metal unit beside a dirt track.
James Parker and Connor Bell carry out an inspection at a pumping station near Howdon sewage treatment works
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Float alarms and sensors can detect stress in the system and prevent sewage overflows by redirecting waste
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But it’s what happens in the cloud, where the data from the sensors is gathered, alongside weather modelling and some very smart artificial intelligence, that the water industry is talking up as the best thing to happen to sewage since Joseph Bazalgette banished the Great Stink from Victorian London.
They call them “smart sewers” and they are the result of a partnership between Northumbrian and HydroDigital, a tech startup from Indiana in the US, where Montestruque said spills had been cut by 85 per cent as part of an attempt to stop storm overflows in the city’s ageing sewage infrastructure — without major new infrastructure costs.
The system, part of an £80 million investment by the utility company, is ultimately designed to tackle the most toxic scandal of our times: the intentional spewing of billions of litres of raw sewage into Britain’s rivers and seas.
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Without “hydraulic relief”, as the deliberate release of raw sewage into waterways is known in the trade, heavy rain would overwhelm sewage treatment works, back up in the network and create flooding, ultimately returning our waste to our bathrooms. The problem is that these spills — from more than 1,000 outlets in Northumbrian’s network alone — are getting worse.
Last year, serious pollution incidents in England rose 60 per cent compared with the previous year, according to government figures, and all pollution incidents were up almost 30 per cent.
While Northumbrian has been one of the better performers, it has seen a rise in all pollution incidents to 105 a year from 2021 to 2024, up from an average of 62 a year from 2017 to 2020.
In July, the company, which is ultimately owned by a Hong Kong-based conglomerate and a private equity firm in New York, agreed to invest a further £15.7 million from its shareholders. It said this “enforcement package” would improve efforts to cut pollution after the water regulator Ofwat said maintenance and operational failures had led to “excessive spills”.
Sewage pollution chokes life in our waterways and poses a health risk to swimmers. One solution is to throw concrete at the problem, building huge underground storage tanks or tunnels. But this is carbon-intensive and costly: London’s now completed 16-mile Tideway Tunnel, which was designed to protect the Thames, will cost its customers about £5 billion.
Northumbrian is trying to maximise existing infrastructure. The new sensors help to create a “digital twin” of its network, showing on screen what is happening in miles of pipes and at hundreds of pumping stations. Analysing a range of detailed weather forecasts for each part of the network allows AI-driven software to present a range of sewage scenarios and propose the best course of action.
Baines shows me an underground pump below a larger opening close to the manhole cover. It’s designed to lift water that flows down into it from surrounding villages up into the bigger sewer. The pump, as well as sluices and gates across the network, can now be controlled as part of the smart system. “So if it’s not raining in this area and we’ve got pressure elsewhere, a signal is sent here and it stops the pump from operating to load the flow back,” Baines says.
By holding back or redistributing sewage in this way, the system can use emptier pipes and existing underground storm tanks to regulate the flow so that less sewage ends up spilling into waterways. Baines likens the system to temporary speed limits that alleviate jams down the road, or Google Maps’s use of traffic data to suggest alternative routes before drivers end up stuck.
Northumbrian says that even in the relatively dry trial period so far, which started in February, the system has prevented 21 spills, amounting to 142,000 cubic metres of sewage — enough to fill more than 50 Olympic swimming pools. It hopes to expand the system to other parts of its network.
“We can’t overemphasise how innovative this is,” says Steve Blanks, the company’s “emerging tech” product manager, who is responsible for talking to tech companies.
Luis Montestruque, co-founder of HydroDigital, said its smart sewer system could result in overspill reductions of at least 25 per cent. The company is based in South Bend, Indiana, where spills have been cut by 85 per cent as part of an attempt to stop storm overflows in the city’s ageing sewage infrastructure — without big new infrastructure costs.
“The health of the river has improved dramatically,” he told me via video call. “We’ve had salmon coming back and there has been a reduction in the concentrations of E. coli.”
Howdon sewage treatment works
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Northumbrian Water is HydroDigital’s first UK client, although Blanks tells me he’s getting regular calls from other curious utility companies, including Thames Water. The American firm has partnered with Belfast-based StormHarvester, which also provides software to water companies, to help deliver the smart sewer system in the UK.
Northumbrian is using technology in other ways as well. In July, the company started sending a robot into its sewers. The “pipebot”, which was developed at the University of Sheffield, can run continuously for up to 30 days, inspecting sewers for damage and identifying potential blockages.
Another project involves the deployment of drones off the coast. The craft have been adapted to scoop up water samples after a storm and return them to a mobile lab on a lorry. Technicians can then map pollution to better understand how spills spread.
Not everyone is convinced by smart sewers. James Wallace, chief executive of the River Action campaign group, said that while they sound promising, “they can’t fix the leaking pipes or neglected treatment works that have been left to decay for years. Until water companies are owned and operated for the public and the environment, not profit, technological fixes are just band-aids on a failed privatisation experiment.”
Back in a drab meeting room at Northumbrian’s Howdon sewage treatment works, which sits on the banks of the Tyne, six miles downriver of Newcastle, Baines and Blanks insist the tech is no fig leaf, and is part of wider investment in infrastructure upgrades. “We live here. We’re all customers too,” Baines said.
Blanks added: “I go paddleboarding and we’ve got colleagues who do open-water swimming. We all care about the environment, and none more than us, because we see what’s happening. We see the challenges, and this is one area where tech can help.”