Specific Activity Bioassays as Tools to Evaluate Combined Nitrogen and Organic Matter Removal in SND Systems

摘要

This article assesses nitrifying and heterotrophic activity potentials, aiming to ward off future efficiency losses in biological treatment systems. For this purpose, we used biomass developed in two-hybrid fluidized bed reactors (FBRs) treating vinasse from ethanol and sugar beet production. FBRs filled with sepiolite and granular activated carbon (GAC) were used with short cycle aeration (25/15 and 15/15min) and different hydraulic retention times (4.9 and 7.4h). At the end of each operational condition, attached and suspended fractions of biomass from both FBRs were collected for activity bioassays. Specific nitrification bioassays suggested that nitrification performance (53-100% for sepiolite FBR and 72-93% for GAC FBR) was associated with the limit of the nitrifiers' potential when the environmental conditions were favorable. On the other hand, low denitrification efficiencies observed in the FBRs (25-44% for sepiolite FBR and 22-65% for GAC FBR) occurred due to low electron availability and the maintenance of residual dissolved oxygen, even during the off-periods, as denitrifiers presented high potential in denitrification bioassays. Assessing biomass potential enabled us to identify at which moment biological capability was close to its limit before loss of efficiency occurred, such as during the reactor start-up or loading reduction/increase. Thus, specific activity bioassays are an important tool for diagnosing biomass potential from simultaneous nitrification denitrification systems to perform aerobic, anaerobic, and anoxic processes.