Ahead of the publication of Ofwat’s Final Determinations on the water companies’ AMP8 Business Plans due on 19^th December, in an Expert Focus article for WaterBriefing Dale Foster and Adrian Heneghan from wastewater treatment specialists HUBER Technology take a look at another potential challenge looming on the horizon for the water sector going into AMP8.

In the wake of massive public, regulatory and political pressure to tackle storm overflows and sewage discharges, another potential challenge is looming on the horizon for the water sector going into AMP8.

We have all been watching as pressure on wastewater companies to tackle the vexed issue of stormwater overflows and sewage discharges has mounted over the last 18 months, driving them to make significant and ongoing financial commitments to mitigate the problems. Barely a week goes by without more positive news from the companies about the practical steps they’re taking and multi-million pound projects already underway or waiting to be rolled out.

However, it has not escaped their attention that another potentially expensive challenge is now rising up the agenda - and like the costly measures being put in place tackle CSOs (Combined Sewer Overflows), they also look likely to be driven by pressure from the public to do something about this one as well.

We are of course talking about the presence of what are often described as “forever chemicals” in the environment – which are also found in large quantities in sewage sludge.

The public, environmental campaigners and media commentators have clearly now taken on board that this sludge is primarily recycled in the form of agricultural fertiliser spread to land. Currently circa 87% of all sludge is recycled to agricultural land as biosolids. It hasn’t taken much for questions to start being raised about the threat to the environment, the food supply chain and human health this is likely to create.

These “forever chemicals”, perfluoroalkyl and polyfluoroalkyl substances (PFAS) - are found in thousands of everyday products and have been finding their way into the wider water environment for decades.

Analysis by the Royal Society of Chemistry has revealed that more than a third of watercourses in England and Wales contain medium or high-risk levels of PFAS, and just more than a third also contain two highly toxic PFAS that have been banned internationally.

EU and US – already taking steps to tackle PFAS pollution

While other countries have already taken significant strides to tackle PFAs pollution in recognition of the multitude of health concerns linked to the chemicals, in contrast progress in the UK has been slow.

The US has introduced a limit of 4 nanograms per litre for perfluoro octane sulfonic acid, or PFOS, and perfluorooctanoic acid, or PFOA. From January 2026, EU member states will have to ensure that the sum of all PFAS in drinking water does not go above a limit of 0.5 micrograms per litre.

However, as with the CSOs, the water companies are aware that the status quo in the UK is unlikely to continue and the current situation could be set to change quite rapidly.

UK moves to put measures in place

In 2023, the Health and Safety Executive identified PFAS chemicals as a risk for consumer exposure and recommended legislation to limit the presence of the chemicals in drinking water. In October 2024, 59 of the world’s leading scientists wrote to the Government urging them to adopt a more ambitious approach to the regulation of PFAS by regulating it as a group.

Now a Private Member’s Bill has been introduced to Parliament calling for legally binding limits on PFAS in drinking water and stronger restrictions overall which will now be read a second time on 24 January 2025.

The implications for UK water companies – threats to status quo and possible worst case scenario?

So, what are the possible implications for the water companies? In addition to the prospect of tighter regulation to limit the presence of forever chemicals in drinking water, one of the key concerns is that tightening regulatory controls could ultimately lead to a worst case scenario of a potential total ban on the availability of land for biosolids spreading.

The risk to biosolids disposal to land during AMP8 has been identified by all companies in the sector. Currently there is ongoing uncertainty about a number of key issues, including:

• Contaminants in sludge
• Farming Rules for Water
• How to manage risk around landbank security for biosolids spreading
• Suitable/appropriate treatment technologies

A Note prepared by Anglian Water for Ofwat in August 2024 following the Draft Determinations on a PR24 Notified Item describes the uncertainty the industry is facing nationally regarding biosolids disposal to land during AMP8.

It also points out that the uncertainty facing the sector is because of both the timing and nature of the expected change which could require significant levels of investment and a coordinated industry response - an uncertainty which is unlikely to be clarified prior to the PR24 Final Determination.

The key drivers for this include potential legislative changes and possible shifting public perceptions which, for example, may impact farmer acceptance of biosolids on their land. Farming Rules for Water (FRfW) are a particular cause for concern – the Note says:

“Within the current guidelines, there is uncertainty regarding the long-term impact of FRfW on the spreading of treated sewage sludge on farmland.

“A Post Implementation Review of FRfW is expected in late 2024 and the DEFRA statutory guidance for FRfW, which (effectively) allows autumn spreading to continue, is due to be reviewed by September 2025. The outcome and exact timing of these reviews cannot be known at present and could be subject to delays. However, these reviews could be the trigger for a significant change to the agricultural outlet for biosolids recycling early in AMP8, resulting in lower land bank availability.

“Change in public/farmer acceptance: There has been a huge increase in interest in biosolids recycling to land. This is particularly notable in the USA and has even resulted in bans on biosolids use in some counties and states. Although the situation is not currently so stark in the UK, there has been a significant increase in media articles and even a Judicial Review launched against the EA/Defra. Such interest has the potential to have an impact on public and farmer acceptance or even make biosolids recycling not viable with little or no warning.”

Cross sector collaboration could be key to mitigating constraints on spreading biosolids to land

We saw these concerns echoed in a presentation we did for the European Biosolids and Bioresources Conference 2023 on landbank security and cross sector collaboration. We looked at a number of possible threats to maintaining the status quo, including:

• Constraints in applying sludge to landbank
• Forced storage of treated sludge
• Contaminants – micro/nano pollutants, pharmaceuticals etc PFAS, POPS, PFOS, PFOA
• Media, campaigners, public opinion

All of the water company respondents who took part in a survey we conducted chose availability of land for biosolids spreading and environmental regulations as their top two risks.

There is currently uncertainty about what technologies could be used if biosolids to land are constrained. So, what are the available options?

Potentially these could include outsourcing sludge related activities including thickening, dewatering, treatment, liming and energy generation. One option which is a growing source of interest to the water companies is the opportunity for cross-sector collaboration with energy- intensive industries like cement manufacture, power generation, chemicals production and paper/ pulp manufacturing.

Cross-sector collaboration already growing in strength across Europe

While there has been relatively little uptake in the UK to date of this approach, this cross-sector collaboration is already growing in strength across Europe where HUBER are already working with a number of different organisations who are putting this in place.

In Germany for example, HUBER are actively involved in the drying of sewage sludge in the Heidelberg Geseke cement plant - the facility also captures emissions from biomass substituting fossil fuels.

Key factors behind the decision to use sludge drying at the plant include:

• reduced use of fossil fuels
• reduced greenhouse gas emissions
• efficient utilisation of heat

Most notably, the process results in the complete material use of the sewage sludge and a significant reduction in process carbon emissions. The use of sewage sludge in the fuel mix provides a very high biomass share which reduced CO₂ emissions from the cement plant by an order of magnitude greater than other alternative fuels. 

No waste is produced by incineration in the cement plant with complete incineration of the sewage sludge taking place within the reaction chamber. Ashes from the sewage sludge are incorporated into the clinker and form part of the cement itself. The sewage sludge firing results in no loss of quality in the cement and savings of around 20,000 t CO₂/year.

An upgrade at the Geseke cement plant is due to start in 2026 with commissioning planned for 2029 when Geseke will be one of the first European cement plants able to produce fully decarbonised cement and clinker. 

Other sludge drying options HUBER are involved in which are already in use in Europe which make use of heat from other energy-intensive sectors include:

• waste heat from IDELUX on site CHP (Belgium)
• waste heat from RWE power plant (Germany)
• waste heat from HVC waste incineration plant (Netherlands)
• waste heat from BASF sludge incineration plant (Germany)

Cross-sector collaboration with energy-intensive industries a useful route for UK water sector

To sum up, while the UK water and sewerage companies are still facing uncertainty at the moment, there are already significant opportunities out there to utilise expertise and waste heat from other energy-intensive sectors. There are some real options on the table which they could have in their toolbox in the event that regulations get tighter and restrictions to spreading biosolids to land grow.

At the very least, it will add to their capabilities to dry and store what could be very significant amounts of sludge while government and regulators decide how they want to move forward on the issue.

Looking ahead, this is a promising technology solution which is already in use overseas but has not yet been taken up here in the UK. As a sector, this could play a key role in helping water companies to manage these challenges while they try to decide the best solution going forward.

At a broader level, it also reflects the Net Zero and circular economy approach the sector is committed to adopting. It also ties in with the strategic approach being taken by the Government, which is currently in the process of setting up a Circular Economy taskforce.