A NOVEL CIRCULATING BED REACTOR - HYDRODYNAMICS, MASS-TRANSFER AND NITRIFICATION CAPACITY

The purpose of this paper is to present the hydrodynamics and mass tra nsfer of a novel rectangular circulating bed reactor as a function of operating conditions and reactor configuration. Within the range of ga s velocities studied (0.01 < U-gr < 0.04 m s(-1)), solid hold-ups up t o 40% v/v did not affect reactor hydrodynamics (liquid circulation vel ocity of 0.3-0.4 m s(-1) and k(L)a in the range 50-300 h(-1)). Moreove r, solid input enhances the local gas hold-up in the downcomer as well as liquid velocity and mass transfer in some operating conditions. Af ter biofilm development, k(L)a does not change significantly compared with values measured in water. Improved hydrodynamics and mass transfe r of the CBR guarantee high nitrification rates and operation stabilit y in three different applications for tertiary (up to 2 kg N m(-3) d(- 1)) and secondary nitrification (up to 0.6 kg N m(-3) d(-1)), as well as in combined denitrification/nitrification treatment (up to 1 kg N m (-3) d(-1)). The good performance of the CBR is highlighted by the sim plicity of the reactor design which does not require any complex techn ical devices. Thus, this innovative and more compact technology will b e an attractive solution for intensive nitrogen and carbon removal for both new compact works and existing plant upgrading. (C) 1997 Elsevie r Science Ltd.