Liquid Distribution and its Effect on the Organic Removal in a Trickle Bed Bioreactor

Propylene glycol methyl ether was removed from wastewater in a trickling bed bioreactor under different liquid distribution conditions. A 0.3 m diameter column filled with two heights of 0.7 m and 1.4 m with 2 cm plastic spheres were used. The wastewater flow rate varied from 0.184 to .0918 kg/m₂.s. The effect of the initial liquid distribution was examined using two types of liquid distributors: a multipoint liquid distributor and a central single point liquid distributor. Over 96 hours of treatment period, the BOD₅ was reduced by 85% and 65% under the most uniform liquid distribution condition and the poor liquid distribution condition, respectively, achieved in this study. Increasing the liquid flow rate from 0.184 to 0.198 kg/m₂.s, it increased the dynamic liquid holdup by 53% and the apparent BOD₅ removal rate constant by 23% at 1.4 m bed height using the multipoint liquid distributor. Moreover, with the use of the multipoint liquid distributor, the apparent reaction when the liquid flow rate was increased from 0.184kg/m₂.s to 0.918 kg/m₂.s. In addition, it was found that the effect of an increase in the bed height on the percentage BOD₅ removal was not significant when initial liquid distribution was uniform. Under the uniform initial condition, only 4% increase in the percentage BOD₅ removal was observed when the bed height increased from 0.7 to 1.4 m whereas when the initial distribution was extremely non-uniform, the percentage of BOD₅ removal was increased by 20% with increasing bed height. The local distribution of the BOD₅ removal was not uniform across the bed cross-section and it was affected by the liquid flow distribution across the bed cross-section.