Full scale fluidized bed anaerobic reactor for domestic wastewater treatment: performance, sludge production and biofilm

This paper describes the performance, sludge production and biofilm characteristics of a full scale fluidized bed anaerobic reactor (32 m³) for domestic wastewater treatment. The reactor was operated with 10.5 m.h^-1 upflow velocity, 3.2 h hydraulic retention time, and recirculation ratio of 0.85 and it presented removal efficiencies of 71 ± 8% of COD and 77 ± 14% of TSS. During the apparent steady-state period, specific sludge production and sludge age in the reactor were (0.116 ± 0.033) kgVSS. kgCOD^-1 and (12 ± 5)d, respectively. Biofilm formed in the reactor presented two different patterns: one of them at the beginning of the colonization and the other of mature biofilm. These different colonization patterns are due to bed stratification in the reactor, caused by the difference in local-energy dissipation rates along the reactor's height, and density, shape, etc. of the bioparticles. The biofilm population is formed mainly of syntrophic consortia among sulfate reducing bacteria, methanogenic archaea such as Methanobacterium and Methanosaeta-like cells.