Simultaneous aerobic and anaerobic degradation of wastewater in a fixed bed bioreactor

An experimental-scale fixed bed reactor, which combines an aerobic and anaerobic processes in a single unit, was developed to evaluate the removal efficiency of biodegradable material from industrial and domestic effluents. The morphology of the support material (silica sand) was also examined before and after treatment by using a scanning electron microscope (SEM). Experimental tests were carried out continuously for a period of 15 days each, varying the mean particle diameter (d(s)), the static bed height (H-s) and the air superficial velocity (U-g). By measuring various physicochemical parameters, the experimental results showed that the highest removal efficiency of organic matter (94-95 %) was attained when the bioreactor operated at d(s)= 1.87 mm, H-s= 0.65 m and U-g= 19.1 m/h. The SEM analysis confirmed that high carbon concentrations were adsorbed by the silica sand after the treatment process, while heavy metals were found to have no association with the sand matrix. The removal of organic matter in the proposed bioreactor was found to be influenced by the in-bed hydrodynamic and operating conditions in the following order: static bed height, air superficial velocity, and bed particle size.