VINASSES BIOLOGICAL TREATMENT BY ANAEROBIC AND AEROBIC PROCESSES - LABORATORY AND PILOT-PLANT TESTS

This paper describes the treatment of vinasses using an anaerobic fluidized-bed, pilot-plant scale, reactor (total volume, 300 liters; bed working volume, 120 liters), and two aerobic biodisc reactors of laboratory and pilot-plant scale (working volumes of 50 and 300 liters). Vinasses fed to the reactors had COD of 60 to 70 g/liter, suspended solids of 11 g/liter, a pH of 4.0-5.0, and a temperature of 20-25-degrees-C. For the anaerobic reactor, removal efficiencies were between 60 and 70%, measured as total COD, with loading rates as high as 20 kg COD/m3 fluidized-bed volume per day, and hydraulic residence times as low as 2 days in the mesophilic range. Biogas productivity reached 6 m3 (STP)/m3 fluidized bed per day with a methane content around 70-85%. For the aerobic reactors, a 2-day retention time was fixed. At laboratory scale, diluted vinasses were continuously fed into the system (around 5 g COD/liter) so obtaining a microbial biomass that contained between 18 and 20% crude protein, with a yield of 1.8 kg wet biomass per kg of COD removed and a depuration efficiency of 65-70% COD and of 95% BOD5. For the pilot-plant scale reactor, undiluted vinasses were continuously fed (60 to 70 g COD/liter) obtaining the same biomass yield with a protein content of 20-30% and a removal efficiency of 40-50% of the total COD and 60-70% of the BOD5.