In October 2018, Iv-Water began with preparing the design of the Energy Factory for contractor Pannekoek GWW, the responsible party for constructing the plant for Water Board Rivierenland. Iv-Water designed the Energy Factory and supported the water board with the environmental permit application. The ambitious goal was to have the Energy Factory operational by the end of 2020. “The volume of sludge that has to be processed is huge”, Ronny explains. “The sludge from nine surrounding wastewater treatment plants will be processed at the Sleeuwijk WWTP, as well as the volume from the Sleeuwijk plant itself. The plant is large, certainly one of the largest in the Netherlands. The intentional scaling up and the bundling of sludge processing is all to do with efficiency, as otherwise, several smaller inefficient facilities would have to be built.

The centralising of the sludge processing and biogas production also means that the sludge has to be transported from various locations to the Sleeuwijk plant. You can transport all of the wastewater there if you want to, but it’s more efficient to separate the water and sludge on location, which saves a lot of transport movements. We indicated this solution as an opportunity in the tender for the project, and this certainly contributed to us ‘winning’ the assignment.”

“Another good example of sharing ideas and thinking on the same lines as the customer is the application for the environmental permit”, says Onno. “During the design process, we gradually realised that if we add this Energy Factory to the WWTP, the preconditions for nitrogen emissions could be restrictive. Within a month, we quickly adjusted the design for our client, which was just in time for the environmental permit application. It was a huge challenge! At ten and even eleven o’clock at night, we were still busy designing and intensely consulting with each other. When the permit was granted, I bought cakes for the whole team. Success must be celebrated! But this is something that is done very well in this project anyway. The atmosphere is excellent, and that certainly benefits the collaboration between all involved! There are many different parties participating in this project: Iv’s team, the water board, the main contractor, and various subcontractors. Sometimes you find yourself in a construction team meeting with up to twenty representatives. It’s fascinating to sit at a table with specialists from so many different disciplines.”

When creating the design for the Energy Factory, Iv made use of market innovations, such as the Ephyra® technology from RHDHV and the anammox technology (NAS-ONE®) developed by Colsen. This project is distinguished by the use of proven technology, in which previous concepts and energy factories have served as a learning curve. “It’s not necessary to reinvent the wheel ourselves every time. What’s important for us is that it works and does what it’s supposed to do. It must be robust. We don’t pull any crazy stunts, and there are no magic-hat tricks, just a solid design”, laughs Ronny. The wishes of the surrounding environment are explicitly considered in the design. The entire plant will remain within a height of 7.5 metres and a building area of 1,500 m². Proven technology has been applied whereby the temperature of the sludge fermentation will remain at around 37 degrees Celsius. This guarantees safety. The Energy Factory will process approximately 150,000 m3 of sludge annually and generate rougly 2,700,000 m3 of biogas. This results in 2,000,000 Nm3 of natural (green)gas, which will be fed into the Dutch gas grid. The plant consists of, among other things, two external sludge buffer tanks, a sludge dewatering building, two digestion tanks and a building containing all the apparatus for the digestion process. In addition, there will also be a buffer tank for the digested sludge, a biogas upgrader facility, a gas holder, a flare system and two sludge silos for storing dewatered sludge.

Shortly after applying for the environmental permit, the Supreme Court ruled that the Nitrogen Action Programme (Programma Aanpak Stikstof or PAS) was inadequate and usage thereof was no longer permitted. Iv-Water rapidly adapted the already submitted design by replacing a gas-fired boiler. In the end, we arrived at recovering heat from the treated wastewater prior to discharge.