Water companies have made mainstream news over the past couple of years thanks to the growing awareness about combined sewer overflows (CSOs), which discharge into waterways during times of heavy rain. Although only one of many contributing factors to poor river water quality, the media and public have jumped on CSOs as a scourge that needs eradicating.
Government, regulators and companies have responded with pledges to eliminate the risk of harm from overflows in the coming decades. Indeed, the sector has been more ambitious than the targets proposed by the Department for Environment, Food & Rural Affairs (Defra) in its plan, currently under consultation. The experts all agreed that significant improvements could be made more cheaply than the eye-watering price tags attached to Defra’s plan – and far sooner.
Nick Mills, head of pollution and flooding resilience at Southern Water, sets out the challenge facing the sector: “The amount of rainwater entering our system during a storm shows the scale of the problem, and the sources are predominantly roof and road-run-off, which are assets we don’t own so we have to work in partnerships to address the problem.”
During heavy rain, this can be a deluge of up to 30 times the normal flow rate hitting a treatment site in medium to high urban areas. “We’ve seen changes in flow peaking at up to 9,000 litres per second at treatment works that ordinarily handle around 300 litres/second. This can cause a host of problems, not only that storm overflows have to be used. Those assets are absolutely hammered in those conditions – nine tonnes a second are hitting the infrastructure. When people hear that they accept that building more infrastructure isn’t the answer.”
The costs mentioned in Defra’s plan on tackling harm from overflows, which ranged between £350 billion to £600 billion, were the price of digging up roads to completely separate sewer systems across the country. In reality the costs could be far lower.
Alternatives to network expansion Mills, who leads the company’s CSO taskforce, says: “We’re trying to prove over the next two years that our approach is more affordable and we can do it quicker.”
He explains that this approach is about understanding the network and assets to optimise each part and improve how other networks such as highways meet with the sewer systems. The next interventions are to tackle surface water by slowing its flow from entering the network, which would reduce the use of storm overflows. This would entail sustainable drainage systems (SUDS) solutions.
Using SUDS could minimise the impact of around 90% of rainfall events in a year while offering amenity benefits, biodiversity and ecological net gain, or carbon reduction benefits, which Mills says can open additional funding sources.
“That is a critical point for pushing this route. We shouldn’t be burdening customers for all of this when we can genuinely partner with others,” he says.
These options would not be as expensive as has been calculated, and the company is launching pilots this summer to prove that. By optimising existing assets the team wants to control what is a passive system.
“This goes beyond our own systems to also consider highway interfaces and connections to us for ways to improve, as well as pumps and electrical equipment.” This could mean operating the networks and pumps differently in anticipation of weather events.
“If we know heavy rain is due, we can empty the system to maximise existing storage; make sure the network gets as much hydraulic capacity as possible; operate pumping stations to maximise pumping capacity.”
The company wants to exhaust optimisation and SUDS before it considers infrastructure approaches such as building more storm tanks, sewers or treatment works capacity. “They’re our last resort but often as an industry we start there because they have guaranteed results. I don’t think they represent best value,” Mills adds.
Nicole McNab, who leads on engagement and communications for Southern, says: “These are the most cost-effective, and also the most sustainable solutions. If we go down the more traditional routes costs will go up – that’s unavoidable. We’re trying to find the best solution for everyone involved.”
Mills explains that the Defra consultation costs presume traditional routes are followed, however this is not the approach companies are considering in the first instance.
“We’re trying to prove there’s another route here, one that spreads costs among those responsible and has added benefits,” Mills says, and adds that the delivery route would be different too. “We won’t go to civil contractors or consultants unless they prove they are doing things differently.”
The company is in conversation with councils about adding SUDS, which has itself opened up conversations about the complexity of the surface water and sewer overflows challenge.
Mills and McNab describe the perceptions many stakeholders have as being perpetuated by “misinformation” in the media that storm overflows are water company problems alone. “We’ve been outspoken about how to address the issue whereas others have been quieter,” Mills says.
“As an industry we need to be bullish talking to people about CSOs; this is as big as the Urban Wastewater Directive for the industry. That was so big it had to privatise the industry to pay for it and I don’t think people are taking this seriously enough.”
Avoiding the blame game
This sentiment was echoed by Robin Price, director of quality and environment at Anglian, who is cautious that blame will be unjustly apportioned. “We need to shout from the rooftops that this is not the water companies’ problems to solve alone, these are societal problems.” He says Anglian welcomes the scrutiny and the conversations but the sector cannot solve this alone. “It is an opportunity to gather data to fuel these conversations that will make a big impact for society.”
Price describes the company’s risk-based approach to CSOs based on data from its network of event duration monitors with spill frequency as one area feeding into the programme of action.
The company has removed 300 of the highest risk CSOs and is using data to build its strategy going forward. As well as monitoring, the company is improving the capacity of its network to hold storm water back and prevent spills.
“As an industry the thinking is moving on now, and recognising that installing storm tanks isn’t the answer,” Price says. “We need to be looking upstream in catchments for solutions. By pointing only at water companies, asking what we’re doing about, it is essentially insinuating that the problem is down to us alone to solve.”
Like Southern, Anglian is exploring how SUDS can be most effectively deployed to manage flows. It ran a surface water management programme in Cambridgeshire town called March that showed 20% of properties’ rainwater systems were misconnected to sewer pipes; 435 highway gullies were also directly connected to the pipes, and there were 24 hectares of impermeable areas such as roads, driveways and roofs that also feed into the sewage network.
To address these points the sector needs to work with local authorities, communities and developers. “There’s so much more to do before we start building concrete tanks on the banks of rivers,” Price says.
He adds that the company welcomes the scrutiny around overflows because it opens up the conversation to show it’s a complex problem. “Yes it’s also a complex answer, but we can only achieve this with working in partnerships. CSOs were designed for a purpose but now we need a 21st century answer.”
Price says there is not yet a tangible shift in understanding or acceptance that the problem goes beyond water companies alone.
“It’s still fairly new, we need evidence and data before we can take that message out. At the moment it’s perceived as a horrific thing associated with water company underinvestment but it’s not at all. These systems were installed decades ago to protect homes and businesses from the menace of sewer flooding, our job now is to find alternative ways of dealing with it by preventing sewers becoming overloaded in the first place.”
Anglian has joined forces with Severn Trent on the Get River Fit campaign that sets out joint pledges to improve water quality.
James Jesic, managing director at Severn Trent and director of Hafren Dyfrdwy, explains that some of these commitments include reducing the number of CSO operations to 20 or fewer by the end of 2025 as well as working to eradicate reasons for not achieving good ecological state on rivers. Accomplishing this will involve increased monitoring of effluent quality from treatment works as well as from CSOs
“Water companies have more to do but we are not the only cause,” Jesic adds. “When I look at the work we do and the money we spend, I think there’s a much greater opportunity to work with other stakeholders and form partnerships to have a much bigger impact.”
As part of the river pledges, the company announced a deal that looks at driving regenerative farming across the Midlands to improve catchment management, land management, reduce phosphate and ammonia run-off that will take a much broader catchment view on river quality management.
“We want to help drive the ecology of our natural environment,” says Jesic. “We recognise the health of the natural environment is key to our business, it’s key to the service we provide to our customers because the better the natural environment the better our product is and the less treatment we need to do, which means fewer chemicals and less energy required.”
This in turn will improve the ecology and natural habitats, something Severn Trent has heralded results from with the reintroduction of otters and beavers.
Credibility and trust
The sector and Ofwat are united on the need for credibility and trust. Jesic says: “We recognise as a company the best way to gain trust and regain credibility is just to be open. One of our river pledges therefore is to share our data: people can access and analyse data on our combined sewer overflow spills.”
He sees education related to the available data as an important part of the narrative for the whole industry – especially given the rise of citizen scientists, but stresses that the information must be accessible and understandable for all. Severn Trent’s River Rangers are a key component to the company’s education approach. They are establishing community relationships that will help with education as well as encouraging people to recognise what they can do such as home improvements that won’t exacerbate flood risks.
Jesic says this will help people make informed decisions about their part in the water cycle.
Addressing credibility was equally high on the agenda for Southern Water’s new majority shareholder, Macquarie, when it acquired the company last year. Mills says one of the first questions Macquarie asked was about storm overflows.
“They saw the writing on the wall and wanted Southern to get ahead.”
This transparency is a double-edged sword, Mills explains, because where Southern is reporting more it appears that the company has more spills than other companies. Given the media attention Southern has received in recent years, Mills recognises the company is under closer scrutiny than most: “Rightly so, our past is our past and it wasn’t good enough. We let people down and the period we were prosecuted for will be referenced for the next ten years, so it’s essential to be really transparent.”