In the context of ongoing criticism from regulators, NGOs, Parliamentary Committees and the public of the water companies’ unsatisfactory environmental performance, HUBER Technology talks about the key role sewage screens play in mitigating the impacts of unauthorised sewage discharges into rivers, lakes and the sea.

In the context of ongoing criticism from regulators, NGOs, Parliamentary Committees and the public of the water companies’ unsatisfactory environmental performance, HUBER Technology talks about the key role sewage screens play in mitigating the impacts of unauthorised sewage discharges into rivers, lakes and the sea.

With ongoing public and regulatory pressure on the water companies, Adrian Heneghan from HUBER Technology looks at practical measures which can help the water companies take improve their operational performance.

Adrian Heneghan: Recent months have seen the publication of Ofwat’s draft methodology for the upcoming Price Review in 2024, and yet more criticism from regulators, NGOs, Parliamentary Committees and the public of the water companies’ unsatisfactory environmental performance.

In addition, the companies are also currently subject to two ongoing separate investigations by Ofwat and the Environment Agency on how Combined Sewer Overflows (CSOs) are being used across their networks.

The sole purpose of CSOs is to discharge untreated human sewage and waste-water when the sewerage system is overloaded – currently there are approximately 21,462 CSOs and pumping stations in the UK (excluding Scotland) (Environment Agency, 2020).

The Government is now getting tougher, saying its Storm Overflows Discharge Reduction Plan Consultation “will revolutionise how water companies will tackle the number of discharges of untreated sewage, which the Government and the public have made clear are completely unacceptable.”

Under the plan, the water companies will face strict limits on when they can use CSOs and must completely eliminate the harm any sewage discharge causes to the environment. Proposals in the plan include:

• By 2035 - the environmental impacts of 75% of overflows affecting our most important protected sites will have been eliminated and there will be 70% fewer discharges into bathing waters;
• By 2040 - on average approximately 160,000 discharges will have been eliminated;
• By 2050 - on average approximately 320,000 discharges will have been eliminated.

The water companies are now facing significant increases in both the levels of investment and practical measures they will need to put in place to tackle the issues which are leading to ever –greater fines, ODI penalties and reputational damage. The Environment Agency is piling on the pressure with a call for prison sentences for company directors in the worst cases and to be struck off.

These are major challenges for water companies which they need to address as a matter of urgency but the reality is they won't be able to do it all immediately.

As the saying goes, Rome wasn’t built in a day, so what can they do in meantime to strengthen the resilience of their existing systems and reduce the risk of the operational failures which lead to pollution incidents?

Supplier point of view – maintain your equipment and optimise your asset health

From a supplier point of view, the key area which immediately springs to mind is ensuring that equipment and infrastructure at all points of the wastewater treatment process are monitored and maintained regularly. Looking at a range of pollution incidents during the last decade, initial equipment failure at a single point in the process which has the potential to cascade and amplify the impacts further downstream has all too frequently been a significant contributory factor.

Screens play a key role in this process, an area where HUBER has developed expertise and industry-leading technologies over years of working with many of the water companies.

Based on our experience, maintaining existing equipment and technologies in place is fundamental to ensure it is in proper working order and stays that way. Simply put, when the risks are ODI penalties, reputational damage, prosecution by the Environment Agency and eye-watering fines, when it comes to asset health, prevention is always better than cure.

The risks are only too real – recent months have seen some significant fines levied on water companies. And this situation is likely to get tougher – the EA has recently called for even bigger fines, prison sentences and company directors being struck off.

Climate change impacts changing low flow levels to high flow levels

Different sites have different requirements – for example, some sites only have static screens with a grill which periodically have to be cleaned manually – these have generally been put in place to prevent waste matter getting to the outfalls which feed into the sea and rivers.

Traditionally, static screen are all in low flow locations – however, the impacts of climate change and more extreme weather events mean low flows are now turning into high flows. As a result, the increased risk means that a lot more solids are now discharging into rivers.

While we do fit static screens where conditions require it, at HUBER, we have a particular focus on supplying power screens which operate on three phase power, which deliver a number of operational advantages compared to static screens.

In our experience, the risks of failure or malfunction in the equipment increase with screens that are manually operated, especially when they don't get cleaned out regularly.

So at sites where the floors are a lot higher and they're in a conservation area, for example, we would always recommend putting a powered screen in place, which includes supplying all the related control and instrumentation equipment , to ensure that all waste material is captured.

This has a key advantage over static screen - material captured via a power screen is kept in the continuation flow and is recirculated, which ultimately prevents solids from going to the outfall.

As part of our work we will generally do a full flow profile consisting of hydraulic profile and size e.g. we may need to size it for 1000 litres a second - for the network for that area, and then work out the equipment needed to deliver the optimum operational performance.

In this context, the data that we get from the water companies is very important so they can tell us what they're actually looking at from a spill point of view - what they are consented to spill to outfall, which can range anything from 100 litres a second and upwards to 30,000, for example.

Sometimes this may also involve retrofitting where there's an existing network but often the utility may be installing new chambers to deal with high levels of flow . The screens we put in are 6 ml 2D screens - anything smaller than that will get into the outfall, but it's mainly about keeping the rag and the solids in the sewer so that only a mixture of rainwater and diluted wastewater goes through when there is a storm event.

And while retrofitting is not always straightforward, we always come up with a solution. Years of work on numerous projects means HUBER has a considerable amount of experience and expertise to draw on and we’re used to overcoming challenges.

With proven equipment that we’ve put installed over the past 30 years (some 1400 units in the UK and even more in widespread use across Europe), it’s true to say that the majority of water companies– if not all – will have HUBER screens in place.

CSO failures – water companies increasingly have no place to hide

At an operational level, pressure on available manpower and resources can have an impact. But failures upstream of the CSO inevitably have a cascade effect resulting in some of the big problems the water companies are being taken to task on.

At HUBER we’re all too aware of what happens in those circumstances, which can often put companies at risk of breaching of their environmental permit. We’re familiar with the problems and the implications of not addressing them swiftly and effectively - and in emergencies we can always move to provide a fast response especially when all the relevant data is provided.

Increasingly, the advent of smart phones and social media mean there’s no place to hide when things go wrong. In one incident we were called out to help with, eagle-eyed members of the public spotted rag floating in the river. Someone swimming in the sea or surfing, or a bathing river, or simply walking alongside can film or take a photograph of what they're seeing and disseminate information about pollution events quickly and widely.

In addition, citizen science data is becoming hugely important – for example, the Environment Agency has established a new citizen science portal, while some of the Rivers Trust groups who are campaigning for bathing water river status in their areas are also incorporating citizen science into their activities.

Whether we’re working directly with the water companies themselves, their Tier 1 partners or external consultants, the ability to work collaboratively on a number of scenarios and come up with the most suitable solution is a key part of our skill set. As part of this we also host Lunch and Learn workshops for individual water companies and their partners - it's a two way process, we get to understand more about their operational processes and challenges, they get to learn more about our technologies and how we can help.

To sum up, interestingly, we're seeing a growing level of interest and uptake in our technologies - no doubt driven in part by the fact that the issue of sewage discharges is now firmly in the forefront of the minds of the Government, regulators and the public alike. It is of course high on the water companies’ agenda and is set to remain there for some considerable time to come.

So while tackling the challenges associated with the eventual removal of some 20,000-plus CSOs will involve a considerable amount of time, resources and investment, in the meantime the water companies have a lot to gain from taking advantage of existing technologies and a supply chain which stands ready and able to help.