RESUMO
A novel biological treatment system was developed for the treatment of piggery wastewater under tropical conditions. It consisted of three consecutive sponge-based floating biofilters. The Upflow Anaerobic/Anoxic/Aerobic Floating Filter (UA3FF) system was shown to be effective with carbonaceous and, particularly, nitrogenous matter. The rationale for the processes occurring in anoxic-aerobic reactors was based on the concept of nitritation-denitritation rather than nitrification-denitrification. The N-related microbial communities manipulated by changing DO concentration and hydraulic retention time were able to effect a considerable increase in the total and specific N-removal (70% and 0.6 kg N m(-3) filter media per day, respectively) as compared to data reported elsewhere. Fluorescence In Situ Hybridization and Polymerase Chain Reaction amplification of ammonia monooxygenase (amoA) gene were used to study interrelationships between N-related microbial groups in the system. Microbiological data was interpreted in terms of operational behavior and performance of the reactors. The N-removal efficiency of the biological UA3FF system was compared with a combined biological/physicochemical system based on (a) biological anaerobic pretreatment followed by (b) a chemical precipitation (CP) and (c) an air stripping. Both systems were scrutinized as to operational advantages and costs. The treatment options could produce effluent of a high quality (202 mg COD l(-1), 126 total-N l(-1) and 89 mg COD l(-1) 48 total-N l(-1) in the biological and combined biological/physico-chemical treatment options, respectively) amenable for the subsequent treatment at the municipal facilities. However, the UA3FF biological treatment system was superior to the combined system by a factor of 20 as far as costs are concerned.
