Optimisation hydrodynamique et choix du support bacterien d'un bioreacteur a lit mobile pour la denitrification de l'eau de mer au Biodome de Montreal (French text, Quebec)

The Montreal Biodome operates a closed mesocosm, the "Saint-Lawrence marine", containing 3.25 million L artificial seawater. Within six years, nitrate levels reached values as high as 180 mg NO3-N/L and the mesocosm was equipped with a 1 m3 MBBR denitrification system in 1998, with the goal of reducing nitrate at levels below 20 mg NO3 -N/L. Denitrification plant never reached expected performances due to hydraulic and biological problems.; The aim of the study was to optimize reactor hydraulic behavior and to select carrier to better control the biofilm thickness. Studied bioreactor is a moving-bed bioreactor, and the carriers on which bacteria grow move freely in the liquid, due to water recirculation injector. No dead-zones and continuous autocleaning of the carriers is required. Packing-bed and moving-bed carriers selection was based on their density, size and shape, and on their surface area.; Video studies with the carriers assessed in defining operating conditions (30% filling ratio and 45° retention grid angle) and in selecting the Cascade 1A and the TriPack 1 for the denitrification experiments. (Abstract shortened by UMI.)...