Effect of Operating Parameters on the Performance of a Thiobacillus thioparus-Immobilized Polyurethane Foam Biotrickling Filter for Hydrogen Sulfide Removal

The effect of variation in the two important process parameters of liquid recirculation rate (LRR) and empty bed residence time (EBRT), on the elimination capacity (EC), and removal efficiency (RE) of H2S from a synthetic waste gas stream in a biotrickling filter (BTF) was studied using Box-Behnken design of experiment. The BTF employed contained Thiobacillus thioparus immobilized on polyurethane foam. The results showed that both the effect of LRR and EBRT on RE and EC depended on the concentration of H2S in the inlet gas stream (C-in). At the lower side of the range 1.85-5.55m/h, increase in LRR always resulted in an increase in both RE and EC; however, over the higher side of this range, at high C-in, increasing LRR did not have a marked effect on RE and EC whereas at low C-in it actually lead to a slight reduction in the value of both parameters. Also, increasing EBRT exacerbated the observed negative effect of high LRR on RE. Contour plot analysis revealed that at low C-in acceptable RE can be achieved simply by reducing EBRT to sufficiently low values independent of the value of LRR. However, at higher C-in the correct setting of the level of both operating parameters is necessary in order to ensure a sufficiently high RE.