Sustainable sediment management in water infrastructures through the innovative "ejectors plant" technology

Preservation of a good navigability in harbours, ports and waterways is a challenging issue. Sediment is currently removed through maintenance dredging, but without being effective in keeping navigability over the time. This objective may be reached through a higher frequency of dredging operations, but would result in higher costs and complex authorization/permit procedures. Maintenance dredging also has considerable environmental impacts: dredging i) greatly modifies underwater habitats and resident flora and fauna, ii) resuspends sediments and contaminants, iii) impacts locally on greenhouse gas (GHG), pollutants and noise emissions. The “ejectors plant” technology has been developed as a sustainable alternative to maintenance dredging and has been recently tested in two different applications in Italy. Both plants were monitored for more than one year to assess i) water depth, ii) energy consumption, iii) maintenance costs, iv) seabed features and species diversity, v) CO2 emissions, vi) underwater noise impact. The minimum water depth required was guaranteed at the end of the monitoring period. Monitoring actions revealed that seabed features and species diversity were improved and that the impact on underwater noise was absent. Finally, an optimized ejectors plant, if fed by renewable power, could cut more than 80% of GHG emissions and guarantee near-zero pollutants emissions in comparison with traditional dredging. The ejectors plant has the potential to be widely applied for the ordinary maintenance of water infrastructures. The paper explores the opportunity to integrate the technology with nature-based solutions and for the combined generation of renewable heating and cooling for buildings.