Treatment of Hazardous Air Pollutants (HAP)s in Ethanol Plant Exhaust by Using a Bio-Trickling Filter

Production of ethanol from the fermentation of corn creates an American produced renewable fuel source. During this process however, hazardous air pollutants (HAPs) are released as exhaust fumes from the fermentation tanks and solids drying. The generated HAPs are composed of mainly a mixture of acetaldehyde, formaldehyde, and methanol in addition to large fraction of ethanol fumes. In order to treat these HAPs, both CO2 scrubbers and thermal oxidizers are currently being used. The current treatment processes use a significant amount of water and energy to operate. In this study, a bio-trickling filter (BTF) is proposed as an innovative industrial HAPs treatment technology that uses less water and energy. BTFs provide a media for bacterial growth nurtured by nutrients supplied by the trickling liquid. They need to be initially seeded with either bacteria from a wastewater treatment plant (WWTP) or a compost. HAPs in an exhaust stream are removed as they pass through the column due to bacterial respiration. A lab-scale BTF has been set up to treat mixtures of HAPs that are common in an ethanol plant exhaust stream. The sampling plan includes 4 locations along the column depth; one at the top, two in the middle, and one at the bottom. Gas chromatography with mass spectrometry (GC/MS) and Fourier Transform Infrared (FTIR) analyzer were used to measure the individual HAP concentrations at each sampling point. Removal efficiency varied by compound and more analysis is needed to determine the effectiveness of the BTF as a treatment method from ethanol plant exhaust.