Activated Carbon Load Equalization of Discontinuously Generated Acetone and Toluene Mixtures Treated by Biofiltration

摘要

Studies were conducted to evaluate use of granular activated carbon(GAC)as a passively operated load-equalization mechanism for biofilters treating gas streams with dynamically varying(intermittent)pollutant loading.In the initial stage of research,abiotic fixed-bed sorption experiments and numerical modeling were conducted to assess the degree of load-equalization achieved by GAC columns for air flows containing intermittent loading of acetone and toluene present as single-component contaminants and as a mixture.In the subsequent stage of research,an integrated system consisting of a GAC column in series before a biofilter was used to treat a gas stream containing a mixture of acetone and toluene at influent concentrations of 430 ppm_v and 100 ppm_v,respectively.To simulate loading conditions expected from an industrial process with intermittent operation,contaminated air was supplied 8 h/day and uncontaminated air was supplied 16 h/day.The system was operated with different empty bed contact times,as low as 2.5 s for the GAC column and 14.5 s for the biofilter.Performance of an additional,conventionally operated biofilter(i.e.,without GAC load equalization system)was used as a basis of comparison.Data are presented which clearly demonstrate that passively operated GAC load-dampening systems installed in series before biofilters can lead to more uniform loading as a function of time and thereby improve biofilter treatment performance.Results also demonstrate that,because of competitive sorption,the degree of load equalization achieved for different constituents in multi-contaminant gas streams can vary markedly.A pore and surface diffusion model(PSDM)was able to accurately predict the degree of load-dampening achieved by GAC columns for single and multicomponent waste gases.