Effect of liquid distribution on the organic removal in a trickle bed filter

Abstract

Abstract The effect of liquid distribution on the biological removal of propylene glycol methyl ether (PGME) in a trickle bed filter was investigated using a 0.3 m diameter column filled with 2-cm plastic spheres. Various liquid flowrates, bed heights (the ratio of bed height to bed diameter H / D = 2.3 and 4.6) and initial concentrations of PGME were used in experiments. The effect of initial liquid distribution was also examined using the multipoint (MPD) and single-point liquid distributors (SPD). The effect of liquid flow rate on liquid distribution, and hence, the BOD 5 removal was found more significant for the short bed ( H / D = 2.3). The BOD 5 removal using MPD increased about 29% when the liquid flow rate was increased from 0.184 to 0.918 kg m −2 s −1 . On the other hand, for H / D = 4.6 with both MPD and SPD, the effect of liquid flowrate on the BOD 5 removal was insignificant although the dynamic liquid hold-up increased about two fold. It was also found that local distribution of the BOD 5 removal corresponded well with local liquid distribution in the bed. In addition, a 37% decrease in the percentage BOD 5 removal was observed while the BOD 5 removal amount increased from 62 to 211 mg L −1 with increases in the initial concentration from 100 to 500 ppm. Based on the Monod kinetic model, the maximum BOD 5 removal rate in the trickle bed filter was found to be 11.7 mg L −1 h −1 and the Monod constant was 759 mg L −1 .