A coming of age for wastewater management

The stormwater overflows scandal has forced water companies to rethink drainage and wastewater management, but what options and innovations are available and when might they be delivered? Ahead of detailed presentations at Utility Week Live in May, Utility Week canvassed the views of industry experts.

With the general public, activists, politicians and even pop stars campaigning to stop the uncontrolled overflow of sewage into seas and rivers, water companies are under unprecedented pressure to develop alternative, more sustainable solutions.

The understandable public outcry has stirred policymakers into action with a raft of new demands. First there were changes to the Environment Act in 2021, followed by a new Storm Overflows Discharge Reduction Plan, published by the Department for Environment, Food and Rural Affairs (Defra) in August 2022, which set out plans to prevent water companies from discharging from storm overflows in or close to “high priority sites”.

How to tackle CSOs will be a major focus topic at Utility Week Live on 17 May. Find out more about the show’s Challenge Programme here.

The first ever Drainage and Wastewater Management Plans (DWMP), submitted to Ofwat in draft in June, and detailing long-term plans for meeting storm overflow targets as part of 25-year investment planning, were sent back to the drawing board by the regulator.

Writing to chief executives in October, Ofwat senior director Aileen Armstrong said plans on storm overflows were “lacking” and failed to include Defra’s new targets, adding that companies “could have developed sensible scenarios that tested a range of likely targets”. She said grey solutions were being prioritised over sustainable or nature-based solutions without sufficient evidence for choices, and that proposals lacked an adaptive planning approach demonstrating how short-term solutions would fit into the longer-term framework.

Companies now have until May 2023 – a two-month extension – to raise their game and submit final DWMP plans demonstrating a more mature approach. These plans are likely to incorporate innovations and lessons learnt from a range of recent testbeds and research programmes.

These include pathfinder projects set up to demonstrate solutions at scale; a partnership trying to overcome the systematic barriers to implementing catchment-wide nature-based solutions; and a drive to open up more water sector data to scrutiny, both by supply chains and the general public.

Dr Nick Mills, head of pollution and flooding resilience at Southern Water, who leads a company taskforce set up to tackle storm water overflows comments: “In future, we expect to see stronger strategic partnerships with local councils than ever before and a more innovative supply chain using people like the Rivers Trust, or council teams, for delivery.” In addition, more standardised designs and off-the-shelf solutions will be “a bit of a game-changer and a real opportunity to stimulate the local economy”, he adds.

Unprecedented strain

Combined sewer overflows (CSOs) have been relied upon for decades to reduce strain on the UK’s dated sewerage system, but as climate change has increased rainfall and water infrastructure has failed to keep pace with population growth, the frequency and duration of overflow discharges have risen (see CSO and PR24 analysis, p30).

According to data from the Environment Agency, 5% of storm overflows spilled over 100 times in England in 2021 and 87% had at least one spill that led to raw sewage entering waterways.

The complete elimination of CSOs is not considered viable – the financial cost alone is estimated by Defra at around £600 billion. Instead, the government advocates a combination of building additional storage, new sustainable drainage systems (SuDS) and alternative measures, at a local or catchment basis, to reduce discharges and prevent ecological harm.

Water companies have already committed a total £3.1 billion for storm overflow improvements up to 2025, which includes more than 800 investigations and 800 improvement schemes. Southern Water has set up a dedicated taskforce to cut its storm overflows by 80% by 2030 and is currently running five pathfinder projects to demonstrate solutions at scale, in parallel with formulating a regional reduction plan.

According to Mills, the concept of adaptive pathways – advocated by Ofwat – is now fundamental to its approach.

Short-term wins will, he says, focus in part on tackling domestic properties and optimising existing assets. Non-permeable driveways are required to have planning permission, but it’s not often enforced, so Southern Water wants to see a national campaign introduced to tackle the issue, working with Water UK and others. “Is there a pumping station control we can change to work better? Is there a storm tank we can make better use of? Could highway gullies be utilised slightly differently?” asks Mills.

Sewers are currently mostly passive in operation, but Southern Water sees an opportunity for more active real-time control using machine learning and algorithms to turn pumps on and off or to open and close valves in the network.

Monitoring will be rolled out to assess the impact of any catchment interventions, says Mills, before deciding on whether to add new grey infrastructure or end-of-pipe solutions, such as storage or treatment.

Arguably the company’s most successful pathfinder trial to date is at Sandown on the Isle of Wight, a catchment responsible for the largest number of storm overflow releases in 2020.

A series of “leaky” water butts, designed to take roof run-off and drain slowly to mitigate peak loads, were installed free-of-charge at customer properties in two areas. The intervention prevented the local storm overflow from activating entirely for a large part of the summer and into the autumn and some 5,000 more water butts have been purchased to scale up the programme.

Natural progression

Nature-based solutions for drainage and wastewater management, like swales, wetlands, and balancing ponds, can be more cost-effective and provide added biodiversity and social benefits, but Ofwat said in its letter to water companies, it had “not seen satisfactory evidence” that water companies “have fully explored such options or provided compelling evidence for discounting them”.

An innovative partnership, between the Rivers Trust and United Utilities aims to define a clearer path forward by removing the systematic barriers that prevent long -term, landscape-scale approaches from getting off the ground.

The partnership was awarded £7 million by the Ofwat Innovation Fund to set up a “catchment systems thinking cooperative” and develop a new framework for gathering data and evidence on the impact of nature-based interventions. It has since expanded to include 12 water companies across England and Wales, and some 30 other organisations, including universities and industry practitioners.

According to Amina Aboobakar, commercial director at the Rivers Trust, who is on secondment from her role at United Utilities, regulatory, funding and affordability barriers include the traditional five-year planning and investment cycle, which prevents long-term thinking and a lack of evidence demonstrating the consistent performance of nature-based solutions.

“Why is it that we are great at creating tactical pilot projects, but fail to transition to scale?” Aboobakar says to Utility Week. “That’s a barrier preventing impact investors and green finance from really coming into this space.”

Creating more opportunities for nature based solutions will be a major focus topic at Utility Week Live on 16 May. Find out more about the show’s Challenge Programme here.

The partnership aims to extend the capabilities of citizen scientists and train volunteers to deliver more standardised methods for catchment monitoring and producing evidence, which in turn will support more strategic planning on where to locate continuous monitoring.

“With more boots on the ground collecting data, we’re going to get a much better baseline,” explains Aboobakar. “If methods are standardised and the data is trustworthy, you can use it for regulatory purposes, for decision making, to report on investment and better understand how to tap into innovation.”

The improved evidence base should help unlock new forms of finance and investment, she adds: “We know these are precisely the sorts of thing green finance and impact investors want to see. We’ve already seen it in the US where, for example, environmental impact bonds brought billions of pounds into coastal restoration and flood resilience.”

A proposed follow-on project looking at other barriers to nature-based solutions, including regulatory, is short-listed for £9 million under the Ofwat Innovation Fund.

Data driven

Accurate data on the operation of wastewater networks is critical to understanding performance, identifying sites susceptible to overflows, and pinpointing where to target future investment. However, such innately inhospitable environments can disrupt sensors and communications, creating anomalies and making it impossible to achieve 100% data quality.

“The more people we have accessing the data, making better use of it and spotting anomalies and making corrections, the better the data quality becomes,” explains Andrew Myers, lead architect at Northumbrian Water, which is spearheading a sector-wide project to develop an open data platform to support data-sharing, collaboration and best practise.

Over the past two years, a consortium of 11 water companies has been designing Stream, a scalable open data framework, funded via the Ofwat Transform innovation fund, intended to help the sector improve transparency, collaboration and efficiency.

Building data infrastructure for digital utilities will be a major focus topic at Utility Week Live on 17 May. Find out more about the show’s Challenge Programme here.

Open data is critical to how water companies respond to the CSOs issue going forward, says Myers: “Various stakeholders have been openly critical of water companies, so we need to have an open conversation on the reasons behind that performance. By being more proactive and publishing information we can show, for example, the spills that have occurred, the investigations we’ve done, and the outcomes we’ve found.”

An initial blueprint for Stream, covering the “enabling” groundwork required to support publication of open data, will be signed off in March 2023. This includes legal and governance matters, definitions for different data sets, agreements for how open data sets can be shared, between companies or between different stakeholders in the supply chain, and compliance with the rules around critical national infrastructure.

“We’re going go back to Ofwat to request further funding,” says Myers. “If we’re successful, we should be able to get a platform up and running in of 2023.” And open data on wastewater networks is “up there” as a compelling initial use case, he adds.

Improved transparency about what is pumped into our waterways and why will be crucial to addressing public concern and, with the other initiatives detailed here, should help forge a path ahead for both the water sector and the communities it serves.


Mansfield SuDs scheme tackles storm overflows

A first-of-its-kind, £76 million water management project in Mansfield will see an array of nature-based solutions implemented to help alleviate pressure on storm overflows and potentially shape the future of flood and wastewater management in the UK.

Sustainable Drainage Systems (SuDs) interventions, including rain gardens, street planters, detention basins and permeable paving will be rolled out in the town through an innovative partnership between Mansfield District Council, Nottinghamshire County Council, Severn Trent Water and other organisations.

The measures, due to be completed in 2025, will be capable of storing a total of around 50 million litres of surface water (roughly 60% of the anticipated network storage required in Mansfield by 2050) and slow and reduce the flow into the waste network during rainfall.

According to Adam Boucher, Green Recovery programme lead at Severn Trent, a key technical challenge was developing blue/green intervention standards for SuDs that have volume capture as the primary driver as well as devising methods to quantify the benefit of each intervention.

Boucher tells Utility Week: “This project has the potential to deliver the blueprint for how we manage flooding risk in the future, reduce storm overflow activations and help rewind the clock following the paving over of permeable surfaces and verges in our towns and cities over previous decades.”