NSI Blog – Blog 3 ‘Waste to Energy’ – Sharing best practices in digestate and water treatment: every project is unique, every solution comes with a challenge

Project example 1: Full-scale digestate treatment from manure

In order to reduce logistic cost for the transportation of treated digestate for land application (through reducing the liquid load and pollution) and meet local discharge regulations, NSI implemented a full-scale digestate treatment installation in Europe. This was designed to separate, clean, and valorize the nutrient-rich residues after anaerobic digestion.

The system integrates decanters, drum filter, MF and RO steps to recover nitrogen-phosphorus-potassium while producing clean water for discharge to the river. The solution has enabled the client to transform a waste stream into valuable products such as biofertilizers, supporting the regional circular agriculture model while reducing logistic cost for the transportation of treated digestate. It shows how a range of advanced separation technologies can reduce cost and recover resources for the best possible business case.

Project example 2: Preparing for advanced wastewater management from municipal & industrial sludge digestion 

Currently in its final installation preparation phase, NSI will deliver a smart process after anaerobic digestion which includes a decanter, pasteurizer, ammonia stripper, and dissolved air flotation (DAF) system into a fully integrated digestate treatment process. Once operational, it will offer a scalable and efficient process wastewater treatment.

The challenge was focused on providing a system to meet local discharge limits, as the effluent from the plant needs to go to a local industrial wastewater treatment plant.

Project example 3: advanced wastewater management and digestate treatment for food waste Anaerobic Digestion plant

NSI is supporting a client who is turning food waste into renewable energy, compliant effluent discharge to the city sewer and nutrients (fertilizer for sale) through advanced integrated wastewater and digestate treatment systems. Wasted food is contributing to greenhouse gas emissions, and a lost opportunity to serve food insecurity. Three operational facilities currently feature a combination of ammonia stripping technology and biological treatment comprising of using MBBR, activated sludge, and MBR configurations.

Here again, the main challenge focused on providing a robust system that always meets local discharge limits, as the effluent from the plant needs to go to a local municipal wastewater treatment plant.

Project example 4: digestate depuration from municipal solid waste

For a municipal solid waste plant, NSI delivered a robust and reliable digestate treatment solution tailored to the site’s challenging feedstock composition. The design focuses on a mix of technologies for centrifuge​, MF, NF and RO and Gac filters. The MF, NF, and RO are based on the patented ‘DEEPEST®’ solutions, a titanium multistage membrane process for treating challenging effluents, achieving high recovery rates and minimally concentrating production volumes.

This project highlights NSI’s ability to engineer durable systems that perform under real-world conditions, ensuring clients meet both operational and environmental targets.

Project example 5: ammonia stripping from digestate from manure

In Europe, a client is digesting agricultural feedstocks combined with a large portion of ‘dry’ chicken manure. Their aim is producing biomethane to be injected into the grid. Due to the high nitrogen content in the feedstock, the client’s challenge is preventing ammonium inhibition in the anaerobic digester, and therewith stagnation of biogas production.

Through delivering an ammonia stripping system (ByoFlex®) including heat exchangers, the system is configured to customer-specific digestate parameters, such as viscosity, operation window and dry matter content. During the initial months of operation, NSI ensures optimal and reliable performance by giving guidance on systems operation.

The project has become a reference point for future developments in the Italian biogas and biomethane sector, combining technical ammonia stripping innovation with proven reliability.

Conclusion – shaping the future of digestate treatment

With each project, NSI reinforces its expertise in transforming digestate management challenges into sustainable opportunities. By applying a combination of advanced technologies—such as decanting, ammonia stripping, DAF, MBBR, membrane system—NSI enables clients to comply with regulations, recover valuable nutrients, and contribute to a circular economy.

Based on the knowledge of NSI’s global technology centers (GTC) Nijhuis, Byosis, Sodai and Econvert, the focus remains the same: delivering smart, resilient, and resource-efficient solutions that help industries and utilities make water and energy work better.

Nijhuis Saur Industries brings integrated solutions to address these technological barriers. With decades of expertise in wastewater, biogas, and resource recovery, NSI delivers complete solutions that combine digestate treatment, water reuse, and biogas purification in one plant.