Treatment of Wastewater with a Low Concentration of Organics Using an Anaerobic Fluidized Bed Reactor

In this work performed in the Laboratory of Sanitation of São Carlos Engineering School- University of São Paulo, the results obtained from the operation of a laboratory scale anaerobic fluidized bed reactor are presented for the treatment of a synthetic wastewater with a mean COD of 557 and 700 mg/l during the two phases in which the reactor was studied. In the first phase (Phase A) the mean hydraulic residence time () was maintained at 1.0 h and in the second phase (Phase B), 1.5 h. The duration of each phase, counted from the initial startup period, was 197 days and 108 days, respectively. The reactor was constructed using an acrylic tube of 1.50 m height and a total volume of 10.5 1. The support material consisted of sand with the grains retained between sieves with openings of 0.210 mm and 0.149 mm. The total height of the fluidized bed was maintained at 1.40 m throughout the experiment. The reactor was operated at ambient temperature (13°C to 31°C), and was fed with synthetic wastewater composed mainly of bovine liver extract, glucose, sodium bicarbonate and ammonium acetate. The results of physical and chemical analyses: pH, alkalinity, temperature, volatile acids, COD, nitrogen and phosphorus are presented. An evaluation was also made during the experiment of the thickness of the biofilm gathered on the sand grains collected over the whole height of the reactor. The mean efficiency of COD removal attained was 62% for the first phase and 71% for the second phase.