Removal of Odor-Causing Substances by a Pilot-Scale Oxidative-Reductive Scrubbing Tower System

Composting is a proven technology for releasing the economic value of kitchen wastes. Following our previous efforts to expand and modify a novel, pilot-scale two-stage oxidative-reductive treatment technology for future implementation as a full-scale tower system, the objective of this work was to examine this scrubber tower system using the optimal operational scenario observed in our previous bench-scale experiments and with two different scrubbing liquid flow rates to allow for its subsequent application at full-scale. As the pH values ranged from 4.0 to 6.0 and from 10.0 to 11.5 in the acidic and alkaline scrubbers, respectively, and the total chlorine concentration ranged from 10 to 95 mg/L as Cl in the acidic scrubber, odor control treatment efficiencies of more than 95% were observed using this treatment technology. A slightly enhanced performance was obtained when a lower scrubbing liquid flow rate being employed, possibly due to the additional contact time between the scrubbing liquids and odor-causing substances in the composting gases. Although a higher scrubbing liquid flow rate increased the possibility of leaking chlorine into the treated gases, which affected the performance of this technology, stronger pH variation and chlorine consumption at the lower scrubbing liquid flow rate indicated the importance of controlling sufficient levels of scrubbing liquid in the system to maintain the treatment efficiency. The results provided insights regarding the use of this treatment technology for minimizing the adverse impacts associated with kitchen waste composting, including the emission of substances that may cause health and/or environmental concerns.