NOMAD is primarily designed to reduce volume, recover nutrients in compact formats and remove harmful pollutants such as antibiotics. The technology was implemented in real conditions, in several biogas plants facilities and with real materials. The integrated solution consisted of different elements that are at different maturity levels (TRL6 for the selective electrodialysis-SED scaled-up unit to TRL8 for the reverse osmosis-RO). Over the course of the project, it was identified that volume reduction is the biggest priority for AD plants, while nutrient recovery came 2nd for large and small plants. Antibiotics was the lowest priority as legislation currently does not require its removal, despite it being of critical importance in the food-water-soil ecosystem. Critical to the design was the limited space and resources on the “mobile plant” which introduced unit size constraints and required compact arrangement of all necessary components. The process was arranged on 2 transportable trailers (T1 and 2) including the heat recovery and digestate pasteurization and solid-liquid separation and the nutrient recovery and the antibiotics removal components (ultrafiltration-UF, SED, UV assisted advanced oxidation-UVOX and RO). The demonstration activities were planned with the operation of the NOMAD trailers in several biogas plants using digestate from different origins (animal residues and manure, agricultural residues, municipal wastewater sludge, food wastes) and undergo all regulatory authorization and operations in four different countries (UK, Greece, Italy and Malta). In the second period of the project all activities related to the demonstration campaigns with the NOMAD mobile plant and field trials at the demo countries were implemented. Major parameters that were critical for the completion of both trailers were time and cost of components and services, with the case of T1 being affected the most due to its complex requirements. T2 travelled from UK to Greece, Italy and Malta for the implementation of the different demonstration campaigns. A series of product streams that could be further exploited were identified (solid fraction of digestate after separation from the liquid, concentrate from UF process, separated ion solutions from SED process (for struvite or hydroxyapatite production), purified water from RO (for irrigation purposes or recirculation back to the biogas plant). A major challenge to be tackled was the removal of the high content of solids, which could cause blocking or damage of T2 units. Additional or alternative advancements are required for digestates with very high solid load. Other aspects are the difference in the capacities of the T2 units. Some of the units are off-the-shelf commercial units (e.g. UF and RO), while others (SED) are under development for this type of applications or could not achieve expected efficiency with dark liquids (UVOX). Moreover, demonstration campaigns showed that if an RO unit could be operated at the final step of the process and at higher pressures (and dissolved solids concentration) it could process more effectively the filtrate from the UF, enabling a higher overall throughput of clean water. Antibiotics are largely detected in the UF concentrate compared to other process streams indicating that an appropriate antibiotics removal unit or process must be added for additional exploitation of a by-product of the process. Field trials with local agricultural soils were organized in greenhouses in Italy, Greece, United Kingdom and Malta with solid fraction of processed digestate, while only small quantities of struvite were produced from the liquid fraction that were inadequate for field trials within the project duration. Results on lettuce yields and morphological parameters highlighted the effectiveness of NOMAD fertilizers/soil amenders that provided similar or better results compared to commercial organic fertilizers. Various routes to market including a range of ownership models and their respective revenue streams and cost savings opportunities have been explored. The results of the project were disseminated through several events (participation in more than 15 national and international conferences with oral and poster presentations, in 9 stakeholder engagement events, fairs and exhibitions, and 6 scientific publications that are submitted or under submission).
