dairy wastewater treatment by anaerobic fixed bed reactors from laboratory to pilot-scale plant: a case study in costa rica operating at ambient temperature

the effect of hydraulic retention time in a range from 1.0-5.5 days was evaluated in a laboratoryscaleanaerobic fixed bed reactor packed with a hybrid material composed of tire rubber and zeolite. underthese conditions, cod removal efficiencies varied from 28.3% to 82.1%, respectively. over the more than 6months of operation, no clogging was observed. the results obtained demonstrated that this type of reactorwas capable of operating with dairy waste at a hydraulic retention time 5 times lower than that used in aconventional digester. based on the laboratory-scale experimental results obtained, a pilot-scale plant wasdesigned. the pilot plant was installed in “cot de oreamuno” near the city of cartago, costa rica.biogasproduced in the pilot-scale anaerobic plant was used for the generation of electricity on the farm. in this case, a cod removal efficiency of 63.6 % was achieved in the full-scale anaerobic plant at a hydraulic retention time of 3 days, this value being comparable with that obtained at laboratory-scale.