Novel Treatment of Odor and Vocs Using Photolysis

Public concerns about offensive odor from livestock operations are on the rise, bringing up an increasing demand on odor treatment. In this work, a bench-scale standard gases generation and UV treatment system was built up, where standard gas mixtures including sulfuric compounds (H2S, methylmercaptan, ethylmercaptan, DMS and butylmercaptan), volatile fatty acids/VFAs (acetic acid, propionic acid, butyric acid and isovaleric acid) and phenolic compounds (p-cresol, 4-ethylphenol, indole and skatole), which have been proposed to be responsible for odor nuisance, were utilized to simulate aerial emissions from swine barn. Permeation tubes that carry unique compounds were weighed around every four weeks and the results showed a stable permeation rate for each compound. Solid-phase microextraction (SPME) fiber was used to sample standard gases, and simultaneous chemical and olfactometry analyses of VOCs associated with odor were accomplished in a gas chromatography-mass spectrometry-olfactometry (GC-MS-O) system. Optimization of experimental conditions including the selection of SPME fiber and best extraction time was performed and thus Carboxen/polydimethylsiloxane (PDMS) 85μm fiber and 10 min extraction was used in subsequent experiments. Gas samples with UV light off (control) and on (treatment) were extracted, respectively, and were sent to GC-MS-O system for analysis. When the total flowrate was 400 ml/min, at 10min extraction, reduction rate for methylmercaptan, butyric acid and p-cresol was 96.2%, 48.15%, 92.16%, respectively, on chemical concentration, and 98.4%, 51.1%, 38.9%, on odor area count and 81.48%, 44.69% and 73.36% on odor intensity count. At 24hr extraction, reduction rate for methylmercaptan, butyric acid and p-cresol was 99.99%, 62.78%, 96.23%, respectively, on chemical concentration, and 74.66%, 45.06%, 93.56%, on odor area count and 69.93%, 40.01% and 88.66% on odor intensity count. To better simulate swine barn emissions and evaluate flowrate effect on UV degradation rate, gases were extracted at higher flowrate, 1150ml/min, 2150ml/min and 3150ml/min. The result showed reduction rate decreased as flowrate increased, but still a very good reduction rate of 79.07% on chemical concentration for p-cresol was obtained at flowrate 3150ml/min, which further verified the powerful treatment effect of UV light on VOCs and odor and feasibility of extending this technique to field applications. Chemical reaction mechanism was preliminarily investigated based on the new compounds identified from the treatment sample, which was accordance with previous studies