English |Dutch en | nl
Home>Insights & News > Overview > From sludge to biogas in the Energy Factory
From sludge to biogas in the Energy Factory Iv-Water

From sludge to biogas in the Energy Factory

Wastewater is increasingly seen as an important source of energy and raw materials. Water Board Rivierenland has set its objective to be completely energy neutral by 2030. To achieve this, an Energy Factory is to be built at the site of the Sleeuwijk Wastewater Treatment Plant (WWTP). “Don’t take this too literally”, say, Onno de Ruiter and Ronny Faasen, of Iv-Water. “We refer to it as an Energy Factory, but it’s actually a wastewater treatment plant. The only difference is that this plant is set up in such a way that the sludge that would normally be disposed of will now be used to generate biogas. This is a big step in making this WWTP more sustainable while more energy is gained, the waste product is reduced, creating fewer transport movements. It’s a wonderful, challenging project, in which sharing ideas and thinking on the same lines as the customer is the winning key.”

Bundling biogas production efficiently

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.”

Celebrate success

“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.

Sludge processing modifications at seven WWTPs

The sludge processing will be modified at seven WWTPs in preparation for fermentation; an extensive job within the entire project. On Monday 17 August, work began at the first plant, Zaltbommel WWTP. “Given that a wastewater treatment plant cannot suddenly be taken out of operation, a temporary processing facility was first set up. The production of wastewater is and will remain a continuous process. After this, the dismantling of the current facility is started. Work continues with the assembly, testing, and operation of the new sludge processing plant. When it is finished, the temporary processing facility is moved to the next location, and the cycle begins again. This process takes place every five weeks and will eventually end up at the Sliedrecht WWTP, by which time it will be March 2021.

The start-up of the Energy Factory is part of the overall responsibility of Iv-Water. Taking on the role of ‘sludge coach’, the start-up is to be implemented step-by-step from October 2020. “We want to achieve high-quality biogas as quickly as possible while continuing to fulfill the primary assignment of the water board: meeting the discharge requirements for treated wastewater.” Besides the start-up of the seven modified plants, training the operators is an essential part of this transition. The Energy Factory is expected to be fully operational by the end of January 2021 and will be followed by a period of ‘interference-free operation’ and demonstrating the performance of the process. “The challenges are sometimes troublesome, but if you tackle them together and celebrate success together, then you can always overcome the (almost) impossible!”, Onno and Ronny conclude.
Would you like to know more about this project? Iwan will be pleased to tell you more. Contact Iwan via 088 943 3200 or send him an email.
We are always on the lookout for new talent. How can you strengthen our team? Working at Iv means working on challenging and varied projects every day. At the office or on location. Check now to see if you can find an exciting challenge within your specialism!