Performance of the UASB reactor during wastewater treatment and the effect of the biogas bubbles on its hydrodynamics

A lab-scale Upflow Anaerobic Sludge Blanket (UASB) reactor was used as a model for evaluating synthetic and complex industrial wastewater treatment, using a solar heater to control temperature. Also, hydrodynamics was assessed using the Computational Fluid Dynamics (CFD) method. Initially, the UASB reactor was operated with synthetic wastewater at Hydraulic Retention Time (HRT) of 24 h in 20 +/- 2 degrees C and 30 +/- 2 degrees C to measure the biogas bubbles production for CFD study. COD removal efficiencies of 85 +/- 3% and 95 +/- 3%, respectively, with production of 27 and 39 ml CH4/h, correspondingly, were observed. After that, the reactor was fed with complex industrial wastewater. It was evaluated at 24 h in both temperatures. At 30 degrees C, low COD removal efficiency was observed, being 48 +/- 13%, with methane production of 20 +/- 3 ml CH4/h. The plug flow pattern was observed in the CFD modelling at HRT of 24 h and 20 degrees C without considering biogas bubbles interaction. Similar hydrodynamic behaviour was observed at HRT of 24 h and 30 degrees C. Nonetheless, when biogas bubbles were considered in the CFD modelling, hydrodynamics significantly changed, passing from a plug flow to a complete mix flow pattern.