Rick Langereis & Marco de Neef
Clean water is essential for our environment and daily need for safe drinking water. This is why the Netherlands has 21 water authorities operating 310 wastewater treatment plants (WWTPs) to purify sewage water and return it clean to surface water. In collaboration with Eliquo, KH Engineering contributes to an innovative solution for HVC. Using residual heat, they will dry sludge from the treatment plants and utilise it as biofuel.
Eliquo designs and constructs comprehensive wastewater treatment plants for Dutch water authorities, delivering holistic solutions for energy-neutral sewage treatment that maximise the recovery of valuable resources. They rank among the top five key players in this sector. The market’s significance is growing due to the Water Framework Directive and the Netherlands’ new Urban Wastewater Directive. Simultaneously, water authorities face substantial challenges in maintaining and replacing sewage infrastructure and expanding wastewater treatment plant capacity.
How a WWTP works
Broadly speaking, a WWTP operates as follows: dirty sewage enters the plant, and the first stage removes large debris and sand. The wastewater is then biologically treated: organic components and inorganic nutrients are broken down by bacteria. These bacteria, suspended in the water, utilise the substances in the wastewater as nutrients for their metabolism and growth processes. After biological treatment, the water moves on to the next treatment stage: sedimentation. Here, the ‘sated’ bacteria sink to the tank’s bottom, while clean water overflows from the top and is discharged into public waterways, ready for reuse in drinking water production. The extracted sludge is then further processed in specialised facilities.
From sludge to granulate
Sludge processing typically involves thickening the material from a very wet state (80% water) to a much drier form (5% water). This is done through several steps, resulting in a granular structure known as granulate. In the Netherlands, only a limited number of facilities can process sludge into granulate. Previously, much of this sludge was exported to Germany for co-firing in lignite plants. With this option no longer available, the Netherlands must expand its processing capacity. To address this, HVC is building a new installation in Alkmaar capable of processing 232,000 tonnes of sewage sludge annually from eight shareholder water authorities.
Innovative solution
HVC has chosen an innovative sludge-drying solution that delivers multiple benefits. As an energy and waste company, HVC serves 52 municipalities and eight water authorities. They assist the affiliated municipalities and water authorities in becoming more sustainable. This is achieved by supporting them in transitioning to ‘gas-free’ and reducing residual waste. HVC’s activities are diverse: from heat development and distribution, the production and supply of sustainable energy, to separate collection, recycling, anaerobic digestion, composting, and the generation of energy from residual waste and sludge. In the new installation, HVC uses the residual heat from the adjacent waste-to-energy plant to dry the sludge, turning it into a biofuel.
Harnessing residual heat
HVC selected the Eliquo – Huber consortium as a partner. Rick Langereis, Eliquo’s managing director, explains: ‘We are currently building an installation that will dry sludge through evaporation, using residual heat (steam) from the adjacent waste-to-energy plant in Alkmaar. At the end of this process, granules are produced, which can serve as a viable biofuel in biomass plants. HVC will use about 30% of this product itself, while the rest is used in other bioenergy plants and cement plants.’
Addressing the sludge surplus
Eliquo has appointed Marco de Neef as project manager for this project, which involves a significant amount of advanced engineering. For this, he relies on the expertise of KH Engineering. Marco notes, ‘This new installation will handle over 20% of the sludge processed by Dutch water authorities, marking a significant step in expanding processing capacity in the Netherlands.’
Collaborative effort
Eliquo possesses extensive expertise in such installations. For this project, they are working closely with the German company Huber, which also brings substantial knowledge to the table. Huber provides the specialised sludge dryers, while Eliquo, together with KH Engineering, handles the complete integration of the installation. In addition to the sludge dryers, the project includes the construction of a reception station for incoming sludge, various systems for the transport of sludge and granulate, equipment for cleaning the drying air, and energy systems for steam, hot water, and condensate.
KH Engineering’s expertise
KH Engineering’s role at this stage is to provide the necessary expertise and skilled personnel. Marco explains: ‘It started with very basic studies; you’re dealing with vapours, substances, explosion risks, and safety standards, so you need to carry out HAZOP, SIL, and ATEX studies. Additionally, there are unique work packages involved. For example, we had to design and procure a specific crane capable of feeding 232,000 tonnes of sludge from the reception bunkers into the drying installation.’ Rick adds: ‘We needed highly specialised expertise and personnel, and we found that at KH Engineering. Beyond the safety studies, this included basic and detailed engineering by specialists in areas such as custom cranes, heat transfer, steam and pressure. Currently, KH Engineering is also assisting us with electrical engineering and process automation. Moreover, they are supporting us during the procurement of equipment from suppliers, the handover of work packages, and in conducting inspections and validations.’
Dedicated team
Eliquo is not only leveraging the knowledge and experience of KH Engineering for this project. In total, around sixteen contracted parties are working on specific work packages. Eliquo’s expertise lies in bringing all these parties together and ensuring the puzzle is completed to deliver a perfectly functioning installation for the client, HVC. Rick explains: ‘To achieve this, we have assembled a dedicated team that works on the project daily. Eliquo is firmly committed to ensuring that all the client’s requirements are meticulously followed by suppliers and subcontractors at every level.’
Climate benefits
At present, the engineering phase has been completed, all work packages have been procured, and suppliers are busy with prefabrication. At HVC’s site in Alkmaar, the civil contractor has nearly finished the civil works, including buildings, roads, and other infrastructure. By the first quarter of 2025, HVC will be ready for Eliquo to begin assembling and connecting the installation on-site. After commissioning, HVC will start drying sludge and producing granulate in 2026, using the sludge pellets as biofuel. This process will make efficient use of residual heat that currently goes unused. Simultaneously, Hoogheemraadschap Hollands Noorderkwartier, one of the sludge-supplying water authorities, will decommission its current gas-fired sludge drying installation in Beverwijk, contributing to additional climate benefits.
Long-term partnership
Rick concludes: ‘We chose KH Engineering for their expertise and capacity, and they deliver on their promises. They honour agreements and maintain an excellent rapport with our team. Their approach is open, pragmatic, and transparent, and they always provide solutions to our challenges. I see this project as the beginning of a long-term partnership with KH Engineering.’
For more information about Eliquo: https://www.eliquo-we.com/en/
ELIQUO Water & Energy develops solutions for public water purification in the Netherlands. By leveraging diverse technologies, they extract energy and valuable resources from wastewater, supporting projects for Dutch water authorities. Beyond the Netherlands, Eliquo is active in other countries, particularly in Europe and Southeast Asia.