Denitrification via nitrite in a modified UASB reactor using Chilean zeolite as microbial support

The general objective of this study was to develop a highly efficient, economical and integrated technology for the removal of nitrogen compounds through denitrification via nitrite. To achieve this, a modified UASB reactor was designed, set-up and operated using Chilean zeolite as microbial support. The results were compared to a conventional UASB reactor used as control. The volume of each reactor was 2 L. The reactors operated with synthetic wastewater under the same operating conditions [with superficial velocities, v[s], of up to 1 m/h] in the first part of the experiment. Later, during the second part of the experiment, only the modified UASB was used, with v[s] of up to 5.5 m/h. In the first part of the experiment, a higher velocity of denitrification in the reactor with zeolite was obtained. Nitrogen removal at the end of this experimental set for both reactors, with a v[s] lower than 1 m/h, was 87%. In the second stage, the modified UASB reactor operated at v[s] of between 1.5 and 5.5 m/h. Here, it was observed that the removal of nitrite increased significantly. Specifically, at v[s] values of 2.5, 4.0 and 5.5 m/h, a value of the nitrogen loading rate [NLR] of 1.22 kg N-NO[2] [-]/m[3]/d was kept constant, achieving nitrogen removal efficiencies of 50%, 65% and 95.5% respectively. This last value proves how highly effective the modified UASB reactor is when operating with v[s] as high as 5.5 m/h

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 laboratory scale anaerobic fixed bed reactor packed with a hybrid material composed of tire rubber and zeolite. Under these conditions, COD removal efficiencies varied from 28.3% to 82.1%, respectively. Over the more than 6 months of operation, no clogging was observed. The results obtained demonstrated that this type of reactor was capable of operating with dairy waste at a hydraulic retention time 5 times lower than that used in a conventional digester. Based on the laboratory-scale experimental results obtained, a pilot-scale plant was designed. The pilot plant was installed in "Cot de Oreamuno" near the city of Cartago, Costa Rica. Biogas produced 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