Evaluation of a new packing material for H 2S removed by biofiltration

Abstract

This study aims to evaluate the feasibility of using a new packing material (UP20) in treating H 2S. Three identical laboratory-scale biofilters, filled with, respectively, UP20 alone, pine bark, and a configuration made of two layers of pozzolan/UP20 (80/20, v/v), were used for critical comparison. Various concentrations of H 2S (up to 100 ppmv) were used to determine the optimum biofilter performances. The superficial velocity of the polluted gas on each biofilter was 65 m h −1 (0.018 m s −1; gas flow rate 0.5 N m 3 h −1) corresponding to an empty bed residence time of 57 s. Changes in elimination capacity, removal efficiency, moisture content, temperature and pH were tracked during 95 days. The pressure drops along each biofilter were also measured by varying the gas flow rate from 0.5 to 4 N m 3 h −1. After 63 days of operation, the loading rate was significantly increased to 10 g m −3 h −1 and the UP20 biofilter retained a removal efficiency of more than 93%, indicating a strong ability to stimulate microbial activity (compared to 69% for the pine bark biofilter and 74% for the biofilter filled with a configuration of two layers of pozzolan/UP20). A Michaelis–Menten type equation was applied and the maximum removal rate ( V m) and saturation constant ( K s) were calculated. V m was evaluated at 35 g H 2 S m biofilter − 3 h − 1 for UP20 (14 and 15 g H 2 S m biofilter − 3 h − 1 for pine bark and pozzolan/UP20, respectively). The saturation constant K s was 70 ppmv for UP20 (18 ppmv for pine bark and 20 ppmv for pozzolan/UP20) indicating that the new packing material will be effective in treating large pollutant concentrations. At low concentrations of pollutant, the results suggest that a biofilter with a configuration of two layers of pozzolan/UP20 is the most suitable choice for treating H 2S.