Determination of transfer rate constants and partition coefficients for air phase biofilters

The determination of transfer rate constants (k) and concentration partition coefficients (k(h)) is required for biofilter mathematical models. A bench-scale technique was developed and used to evaluate k and k(h) values for four different packing materials: (1) compost; (2) a mixture of compost and diatomaceous earth (DE); (3) Calgon granular activated carbon (GAC); and (4) Westates GAC. Two vapor phase contaminants were used: ethanol and carbon dioxide. Experimental results showed that this technique produced estimated kh values that were similar to both ''batch'' and ''spike test'' results, indicating the accuracy of the procedure. Calculated k(h) values for carbon dioxide were two orders of magnitude less than those for ethanol. The water content of the packing material strongly affects k(h) values. High water content increased k(h) values for ethanol and decreased k(h) values for carbon dioxide.