GASEOUS CAH REMOVAL BY BIOFILTRATION IN PRESENCE AND ABSENCE OF A NONIONIC SURFACTANT

The objectives of this study were to investigate the biodegradation of gaseous trichloroethylene (TCE) and tetrachloroethylene (PCE) in an a ctivated carbon biofilter inoculated with phenol-oxidizing microorgani sms and to study the effect of surfactant concentration below its crit ical micelle concentration (CMC) on the removal efficiency of TCE or P CE. For the enhanced biofiltration, a biodegradable nonionic surfactan t was added to biofilters. The investigation was conducted using two s pecially built stainless steel biofilters, one for TCE and the other f or PCE. The removal efficiency of gaseous TCE was 100% at a residence time of 7 min and its average inlet concentration of 85 ppm. For gaseo us PCE, 100% removal efficiency was obtained at residence times of 4-7 min and its average concentrations of 47-84 ppm. It was found that ad sorption by GAC and absorption by influent nutrient solution were a mi nor or negligible mechanism for TCE and PCE removal in the activated c arbon biofilters. The TCE and PCE activated carbon biofilter performan ces were observed to be a little enhanced but not significantly, when the surfactant was introduced at concentrations of 5-50 mg/l. Surfacta nt concentrations of 5-15 mg/l were found to be an optimal dosage in t he biofilter operation for avoiding significant residual in the efflue nt from biofilters.