Influence of bioparticle size on the degradation of partially soluble wastewater in an anaerobic sequencing batch biofilm reactor (ASBBR)

An evaluation was made of the influence of bioparticle size on the degradation kinetics of a partially soluble synthetic wastewater in an anaerobic sequencing batch biofilm reactor, mechanically stirred, containing immobilized biomass. The 4.5-L reactor was operated at 30 °C, with biomass immobilized on cubical polyurethane foam matrices (0.5, 1.0, 2.0 and 3.0 cm sides) and mechanically stirred by three flat-blade turbines (6 cm) at an agitation rate of 500 rpm. The COD of the synthetic wastewater was 1000 mg/L (50% suspended). The apparent first-order kinetic constants (k1app), calculated for filtered and suspended COD, did not show the expected tendency (smaller the particle, higher the coefficients). For suspended COD, the maximum k1SSapp occurred with 1-cm bioparticles. This particle size probably favoured better foam packing, enhancing the hydrodynamic conditions and dissolution rates. In filtered COD, the maximum k1Fapp occurred with 2-cm bioparticles, which was attributed to the correlation between the foam packing and the conventional and nonconventional mass transfer phenomena. Even then, a kinetic analysis of individual substrates (carbohydrates, proteins and lipids) revealed the expected tendency.