"A novel reactor configuration for the enrichment of anammox bacteria from marine sediments was developed. Marine sediments were successfully kept inside the bioreactors during the enrichment process by strategically installing traps at different depths to prevent the wash-out of sediments. Three up-flow anaerobic sediment trapped (UAST) reactors were set up (α, β and ω supplied with 50, 150 and 300 mg Ca2+/L, respectively). Nitrogen removal rates (NRR) of up to 3.5 g N/L-d and removal efficiencies of >95% were reached. Calcium enhanced biomass production as evidenced by increased volatile suspended solids and extracellular polymeric substances. After the long-term operation, dominant families detected were Rhodobacteracea, Flavobacteracea, and Alteromonadacea, while the main anammox genera detected in the three reactors were Candidatus Kuenenia and Candidatus Anammoximicrobium. The UAST reactor is proposed as suitable technology for the enrichment of anammox bacteria applicable for the treatment of saline industrial wastewaters with high nitrogen content."