Improving the efficiency of aerobic biological treatment of domestic wastewater by using fixed culture media

This study investigates the use of pozzolan, a volcanic slag, as a packing material in a fixed culture system for biological wastewater treatment.Experimental work was conducted to evaluate the performance of pozzolan in terms of removal of biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD) and NH 4 + under different substrate concentrations and bed heights.The results reveal that pozzolan achieved BOD 5 removal efficiencies of up to80% at a concentration of 1g/L with a 20 cm bed height, while COD degradation rates demonstrated a kinetic constant K of 0.080 min -1 under the same conditions.At higher concentrations (1.5 g/L) and a 40 cm bed height, the performance was slightly reduced, with COD degradation exhibiting K = 0.040 min -1 , likely due to substrate saturation effects.Comparatively, scoria showed lower efficiency, with kinetic constants ranging from 0.018 to 0.065 min -1 , highlighting the superior performance of pozzolan as a packing medium, NH 4 + .