Mitigating Harmful Storm Overflows

As Ofwat places further pressure on wastewater companies to reduce their combined sewer overflows, Louis Larsen, Digital Sales & Business Development Manager at Veolia Water Technologies outlines some of the innovative technologies available to make vital improvements to sewerage systems.

In Ofwat’s PR19 final determinations, at the start of the AMP7 period, Ofwat incentivised wastewater companies to better understand the flood risk in their region and develop long-term strategies to reduce the risk. New reporting guidance was also published so that companies could report on the risk of sewer flooding during an extreme wet weather event accurately and with a common approach.

Furthermore, at the end of 2021, the Environment Act was introduced in England which includes new duties for water companies to demonstrate progressive reductions in the adverse impacts of sewage discharges from storm overflows, as well as further requirements to report on the storm overflows that do occur.  

In the years since, a number of companies have been commended for their commitment to reducing spills from combined sewer overflows (CSOs) to an average of 20 per year by 2025 and are already on their way to achieving this aim. However, the effects of climate change and an increasing number of extreme weather events is making this a more difficult feat to achieve for others. 

While nature-based solutions, such as SUDs, are available and should be maximised where possible, another way to reduce the use of CSOs is by implementing a digital monitoring system that can more effectively manage sewerage networks generally or even offer real-time optimisation so that immediate remedial action can be taken. 

Our Solutions

Hubgrade is a smart digital monitoring and optimisation service that can be used on a single technology, a range of equipment or a complete sewerage system. It combines advanced digital tools, such as IoT sensors and artificial intelligence (AI), along with the expertise and technical know-how of our water treatment specialists to deliver optimal operational and environmental efficiency. 

Utilities facing increasing challenges with storm overflows can benefit from the digital sewer network twin that can be created using specific modules in Hubgrade’s Performance service. Modules such as Sewer View and Sewer Flex work to provide a dynamic overview of the complete sewerage network while also generating knowledgeable insights through a data-driven approach, cloud computing and AI. Ultimately, through the Sewer Flex module, real-time optimisation of the network can be achieved, allowing for the full utilisation of the network’s storage capacity, by taking into account the weather forecast, the hydraulic model across the various locations, economic and environmental factors.

Furthermore, many utilities plants lack a centralised, visually accessible overview of their sewer network. While many plants store and gather data via GIS and SCADA systems, this information is not always centralised, sorted and analysed for operational improvement. Hubgrade can bridge the gap between information gathering and using that data to generate real operational improvement. 

Case studies

Sewer Flex has already been intrinsic in tackling storm overflows across a number of sites in Denmark. BlueKolding wastewater treatment plant (WWTP) implemented Sewer Flex across its portfolio and as a result, managed to reduce its number of storm overflow events from 35 to just 10 events per year. Moreover, the Sewer Flex installation has resulted in a 50% saving in capital investment when compared with the alternative solution that BlueKolding was initially considering, which involved constructing a basin for overflow reduction. Read this case study here.

Hubgrade Performance Sewer Flex has also been used by BIOFOS WWTP in Copenhagen to significantly improve operations and reduce environmental impact. Set up to provide an inflow forecast for the site’s catchment, the Sewer View system analyses the forecast and activates Stormwater Mode in advance of a storm event, substantially increasing the site’s hydraulic capacity. With a forecast horizon of two to six hours, this mode has enabled BIOFOS to dramatically reduce its storm overflow discharges into the local environment. The holistic optimisation capacity of Hubgrade Performance enables utilities companies to make the most out of existing systems. It also grants operators peace of mind that their assets can handle the dynamics of the load in their system without their active intervention, by providing them with full insight into what is happening at all times. 

Similarly, Sewer View has been utilised by the municipality of Rudersdal in Denmark to implement a number of infrastructure changes in order to be better equipped to deal with storm events. As part of a measurement campaign of Rudersdal’s sewerage network, 40 flow measurement points were set up to gather information on the number of storm overflow events that took place over the course of a year. All of the data quality checks and reports were produced by Sewer View and these are helping the municipality to plan and future-proof the local vicinity.

Ofwat will continue to closely monitor how sewage treatment works are managed and the use of CSOs over the coming months. Progress made will likely be used to set future performance benchmarks on storm overflows and inform Ofwat’s proposals for its performance commitments for PR24, alongside the expectations of the Environment Act 2021. 

Getting a head start on implementing digital monitoring solutions will help utilities companies avoid significant penalties as well as reducing the impact of climate change on operations both now and in the future. 

For more information and to discuss the options available, contact one of our experts here.