Scale-up and cost evaluation of a foamed emulsion bioreactor

In the present paper, the potential of the foamed emulsion bioreactor (FEBR), a novel biological reactor for air pollution control was evaluated. Experimental data obtained on a laboratory-scale prototype were used to scale-up the process for a hypothetical case consisting of a contaminated air flow rate of 10,000 m(3) h(-1), a toluene inlet concentration of 1 g m(-3) and minimum required treatment efficiency of 92%. Reactor design and operating issues for the full-scale FEBR were identified. They included the requirement for stable foam generation with appropriate air distributors, and recycling of the auxiliary organic phase, surfactants and cells from the discharge of the reactor. The capital and operating costs for the concept full-scale FEBR were evaluated and compared to those of competing technologies, namely biofiltration, biotrickling filtration and catalytic and thermal oxidation. All three biological techniques had significantly lower capital and operating costs. Among the biological techniques, the FEBR had the lowest estimated capital cost since its greater effectiveness allowed a smaller reactor to meet the treatment objectives. The operating costs for the FEBR were higher than those of biofilters and biotrickling filters because of the requirements for nutrients and auxiliary chemicals. Overall, the results highlight that biotreatment is much more cost effective than thermal and catalytic oxidation. They further suggest that the FEBR may an interesting alternative to biofilters and biotrickling filters where the available space for air pollution control equipment is limited.