Engineers urge UK action on sewage to guard against sickness outbreaks

Protesters on Gyllyngvase Beach joined thousands on beaches across the country in a paddle-out protest against sewage pollution through a Surfers Against Sewage campaign

IMMEDIATE action to bolster maintenance of the sewage system and sensors to allow real-time monitoring of water quality are among engineering experts’ recommendations to reduce the risk of harmful organisms polluting UK’s waterways and making people sick.

Engineers assembled by the Royal Academy of Engineering (RAEng) ranked the costs and effectiveness of a range of wastewater measures for their report, Testing the waters, which was released today at a time of increased scrutiny for the UK’s water industry.

David Butler, chair of RAEng’s National Engineering Policy Centre working group on wastewater, said: “Growing urbanisation and forecasts for more frequent and intense rainfall events due to climate change will mean increasing pressure is put on our ageing wastewater system. Policymakers and industry should carefully consider the actions we have outlined here and their implications in future wastewater infrastructure projects.”

Sewage spills and public health

The recommendations come amid heightened pressure on the water industry to stop spilling sewage into waterways. Last year, industry spilled sewage into the environment through storm overflow pipes at a rate of 1,271 times a day.

This is one of two routes that introduce so-called faecal organisms from human sewage into the environment. The other is the treated effluent that is continuously discharged from wastewater treatment plants. These plants reduce the concentrations of harmful bacteria and viruses but do not eliminate them.

With the water system and those who operate it justifiably under fire for the environmental pollution caused by spills, the report’s contributors underscore that sewers have saved millions of lives by preventing faeces from contaminating drinking water, massively reducing outbreaks of cholera and typhoid.

With water companies set to invest £96bn (US$122bn) between 2025 and 2030 to meet the water regulator’s demands to reduce environmental pollution and boost water supplies, the report’s contributors said now would be a good time to bolster the public health benefits too.

Sir Chris Whitty, chief medical officer for England, said: “For several decades now, the principle thing that the system has been designed to do is reduce environmental impact. Our view is actually we should rebalance this so that the public health elements are part of the decision-making as to what investment goes where.”

He acknowledged that the evidence base is “quite thin” because it is difficult to trace an individual person’s illness to a specific leak. Despite this, he said engineering interventions should be targeted to minimise risk where people are most likely to be exposed.

Sir Chris said: “We’ve just been through one major pandemic. I’m not suggesting we’re going to go through another one led by the sewage system, to be clear. But I think it reminds us that thinking about all of the routes of transmission and minimising the risks down those routes is very sensible.”

What are the engineering recommendations?

Engineers, policymakers, and representatives from the water industry and environmental groups reviewed how the hazard of human faecal organisms in public waters can be reduced or how to minimise the public’s exposure to it. In the Testing the waters report, engineers scored each intervention for how expensive it will be to build and operate, plus how much it would reduce risk.

Top of its list for immediate action is that water companies must prioritise maintaining their assets. This includes fixing cracks in pipelines that allow groundwater to seep in, increasing the volume of water that the sewage system must process. This can lead to overflow pipes having to discharge raw sewage to the environment to prevent the system becoming backed up and flooding homes.

The authors estimate the nationwide cost of implementation would exceed £100bn. They use nationwide estimates for comparison purposes but note they are not suggesting any of the incentives be deployed exhaustively. The choice of implementation would depend on local conditions, including scale, geography, policy priorities, and affordability.

Next up, they want government to accelerate the rollout of environmental monitoring and extend the scope so that regulators monitor the microbiological quality of treated effluent. While the report notes that real-time measurement of microbiological pollution is still in its infancy, Butler said it would help to begin field testing the technology alongside sensors that are already available to measure the likes of pH and dissolved oxygen. A public alert system could be developed that would warn people in real-time whether bodies of water are unsafe to use. It would also help provide data that engineers could use to monitor and improve the performance of treatment systems.

Disinfection processes could be used to reduce the concentration of faecal organisms released from overflows and effluent discharge. The opportunity for risk reduction is high, yet so is the estimated expenditure. UV radiation would be the most cost- and carbon-effective choice. The report calls for water companies and regulators to consider which sites might best use these technologies as part of a public health risk-based approach to improving wastewater infrastructure.

Room for improvement on digitalisation

Data and digitalisation are frequently mentioned within the 16 interventions assessed in the report. The authors note that real-time control would allow industry to operate proactively by coordinating storage assets at pumping stations to manage and buffer high flows of water into the system during storms and prevent overflows.

However, the sector has been slow to implement digital technologies and there is a lot of scepticism within industry about the level of digitalisation and automation that can be achieved.

Butler said: “There is a lot of headroom for improvement. I think historically, the water industry generally has been very conservative in the way that it operates its system…They are at the beginning of their journey. But we see lots of potential.”

Think long-term

Among the 15 recommendations made in the report, the authors warn government that its call to build storage tanks to prevent overflows should only be used where environmental and public health risks are greatest and there are no acceptable alternative actions.

“They address the symptom not the cause,” Butler said. “The wastewater infrastructure is a long-term infrastructure so short-term solutions need to sit within a much longer-term plan.”

Sewage overflows could be reduced if rainwater was prevented from entering sewers. Existing sewers could be separated so that surface water flows into its own system, but the authors warn that it’s a high-cost option and digging up roads would be hugely disruptive. Local authorities and regulators could copy the Netherlands where homeowners have been incentivised to regreen their properties to help capture water by removing patios or paved-over gardens.

Looking longer-term, the authors call for government to develop an overarching vision for the UK’s wastewater system. This needs to balance human health and wellbeing, protection of nature, security of supply, flood resilience, economic sustainability, and customer satisfaction and be supported by measurable targets to monitor delivery.  

Andrew Thompson, an IChemE Fellow and member of the NEPC working group that compiled the report, said: “Making a positive and important impact to the science of protecting public health is already at the forefront of many chemical and process engineering industry sectors, and our profession’s unique ability to take a systems-thinking approach is crucial when – like with wastewater – there is no single solution on offer for all scenarios.

“Research data and new technologies will be key to delivering efficient and cost-effective results, in addition to ensuring that our future chemical and process engineering talent are equipped with the right skills and ability to meet difficult challenges.”