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From TAGs to riches – the Orège solid-liquid-gas story

  • From TAGs to riches – the Orège solid-liquid-gas story

About the entity

Isle Utilities
Innovation consultancy specialising in the development and commercialisation of emerging technologies in the water & environmental sectors.

Many wastewater plant operators such as Yorkshire Water are on the hunt for innovative strategies to combat increasing sludge haul and disposal costs, as well as rising polymer costs and tightening regulation. The Orège SLG system is a very simple technology that provides a short economic payback (typically <5 years) by reducing sludge volume for hauling and disposal whilst decreasing polymer consumption and increasing throughput and solids capture rate.

Orège Ltd presented its technology to utilities in the UK and USA between 2015 and 2019 at the Technology Approval Group (TAG) event hosted by Isle Utilities. The TAG group is an innovation forum of the world's leading end-users accelerating the market uptake of step-change technologies by engaging the industry during the pre-commercial stage of development. Isle operates TAG forums for water utilities in different regions around the world.

Orège and Yorkshire Water partnered in an innovative pilot trial with an exciting technology that reduces sludge volume and lowers WWTP operating costs

Once the TAG group has connected the technology developers and the technology seekers the obvious next step is a trial! Thankfully the Trial Reservoir is here to make this happen. The Trial Reservoir is an initiative also founded by Isle Utilities in 2021 to provide risk free loan funding specifically for trials. The trials gain commitment from an end user before the trial starts, ensuring the technology won’t be wasted if the trial is successful. If the trial is unfortunately unsuccessful, the loan is written off, making this opportunity very low risk for the technology companies involved.

Orège and Yorkshire Water partnered in an innovative pilot trial with an exciting technology that reduces sludge volume and lowers WWTP operating costs. Orège develops technologies and proprietary solutions for the conditioning, treatment, and recovery of urban and industrial sludge. Headquartered in France, they support the water industry internationally from their offices in France, the UK, the USA, Italy and Germany.

Aims of the trial

The aim of this trial from Yorkshire Water’s perspective was initially to demonstrate the technology and to purchase one package plant thickening unit, with the view to identify how the technology could be used within the wider business.

At the start of this collaboration, Yorkshire Water wanted to find new solutions to reduce the volumes of tankered sewage sludge being removed from their sewage treatment works by road.

This trial offered an opportunity to improve the current operations and safeguard the site for changes, in both the short- and long-term future.

Traditional solutions to sludge thickening on many sites have proved costly, and the assets involved are not always well suited to resolving common challenges on these sites. Yorkshire Water is always looking for ways to increase efficiency within their operations; thanks to the Trial Reservoir initiative, the utility was provided a unique opportunity to make this happen by using Orège’s new package plant thickening technology.

SLG uses air and energy exchange to modify the sludge rheology and create an emulsion. The bound water is released and the SLG sludge floats. Next stabilising polymers are added, which completes the flocculation process. The SLG sludge is then treated by the dewatering equipment already in use on the plant.

This trial of Orège’s unique technology started in May 2022, focusing on municipal sewage sludge. The SLG technology is a sludge conditioner that can be integrated with existing thickening and dewatering equipment.

Thanks to the Trial Reservoir initiative, the utility was provided a unique opportunity to make this happen by using Orège’s new package plant thickening technology

The trial lasted for two months and during the trial period, Orège and Yorkshire Water sampled the feed, thickened sludge, filtrate solids, and filtrate in order to analyse dry solids (DS), phosphorus and ammonia. The trial’s success factors included satisfactory filtrate and solid quality, and the ability for all the sludge to be tankered and offloaded successfully with each full load taking no longer than 15 minutes on average to unload at the import site.

The SLG unit was required to cope with rags and grit, to consume no more than 183 kWh energy per day, and require a maximum polymer dose of 4.5 kg/TDS liquid polymer.

Lastly, it was required to operate unattended for 95% of the trial period, with all operator tasks taking no longer than 15 minutes per day.

Throughout the trial Yorkshire Water applied this technology to primary sludge and implemented it at one of their sewage treatment sites. Yorkshire Water imports sludge from around 700 water treatment sites and have found several sites that would be specifically suitable for this technology. The adoption of this technology will allow Yorkshire Water to significantly reduce sludge movement. Currently, at one site, 15,000 tonnes of sludge are exported per year. This technology allows the volume transported to be halved, reducing diesel use and emissions. Additionally, less energy will be used in the dewatering process which means a huge decrease in the overall greenhouse gas emissions of Yorkshire Water.

The success of the trial

The trial itself became a long but worthwhile journey for everyone involved.

The positive impact of this trial has massively contributed to Yorkshire Water’s carbon reduction targets. The current sludge import process involves driving around Yorkshire transporting sludge, which creates emissions from the diesel engine fumes. This trial focused on just one treatment site in Yorkshire Water’s portfolio and has already heavily reduced the amount of sludge transportation needed. Resulting in the equivalent of removing 40,000 kg of CO₂ per year from their business-as-usual operations. Imagine the amazing results that could be achieved by using this technology in all the suitable Yorkshire Water wastewater treatment works!

Through the successful trial and implementation of this technology on one site, Yorkshire Water has the confidence and assurance to begin purchasing and rolling out this technology on many of their other sites facing similar challenges. The performance of this technology led to a 50% reduction in sludge volume needing to be hauled for disposal without causing any indirect issues in the upstream and downstream process unit operations. This will result in a six-figure OpEx saving for Yorkshire Water over the lifespan of the asset.

Richard Glossop from Yorkshire Water stated: “We are always striving for innovative ways to improve our wastewater treatment processes, with the aim of providing better value for our customers and achieving our carbon net zero goals. This trial gave us a clear and defined route from trialling the technology to implementation and the results have been positive, with a significant reduction in sludge transportation requirements and a reduction of costs and emissions in the process. We are already looking at rolling the technology out at other sites around the region and look forward to an ongoing relationship with Orège.”

The performance of this technology led to a 50% reduction in sludge volume needing to be hauled for disposal

From the completion of the trial, it is safe to say that all parties have viewed it as a success with ambitious expectations of how this technology can be further implemented, transporting Yorkshire Water closer to its carbon neutrality goals.

To find out more about other successful Trial Reservoir trials please visit:

Or get in touch with the Head of Trial Reservoir Jo Burgess here:


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