Emission of odorous volatile organic compounds from a municipal manure treatment plant and their removal using a biotrickling filter

Composition and profiles of volatile organic compounds during waste decomposition by the anaerobic bacteria purified from landfill

Volatile organic compounds (VOCs) become concerned pollutants in landfill gases, and their composition and concentration varied significantly during waste decomposition. Many environmental factors are known to affect VOC emissions, while the effect of indigenous bacteria in wastes on VOC production remains elusive. In this study, a simplified anaerobic degradation experiment, with the single substrate and the purified bacteria from a landfill, was set up to measure the degradation process and the dynamic changes of VOCs. The experiment excluded the abiotic factors for VOC variation. The two isolated bacteria, identified as Sporanaerobacter acetigenes and Clostridium sporogenes, could anaerobically ferment amino acids by Stickland reaction. They produced 51 and 57 species of VOCs in the experiment, respectively. The concentration changes of VOCs over bacterial growth and fermentation were clustered into four types by principal component analysis: three profiles were regular, similar to the variation of nitrate, hydrogen sulfide, and the major fermentation products (carbon dioxide, ammonium, and volatile organic acids), respectively; while one profile was unique to any degradation indicator. The various concentration profiles indicated different origins for VOCs, possibly from the extracellular environment, fermentation, and secondary reactions. The findings provide insights into the understanding of VOC diversity and variability during waste decomposition.

Characterization of Volatile Organic Compound (VOC) Emissions from Swine Manure Biogas Digestate Storage

Livestock manure is one of the major sources of volatile organic compound (VOC) emissions; however, characteristics of VOCs emitted from biogas digestate (BD) storage, which is a common manure practice, remain unclear. The objective of this study was to characterize VOC emissions during BD storage through the dynamic emission vessel method, to identify the VOC emissions that have potential odor and/or toxic effects. The results revealed the detection of 49 VOCs with seven classes, whose total concentration varied from 171.35 to 523.71 μg m−3. The key classes of the 49 VOCs included Oxygenated VOCs (OVOCs), olefins and halogenated hydrocarbons. The top four compositions, accounting for 74.38% of total VOCs (TVOCs), included ethanol, propylene, acetone and 2-butanone. The top four odorous VOCs, accounting for only 5.15% of the TVOCs, were toluene, carbon disulfide, ethyl acetate and methyl sulfide, with the concentration ranging from 13.25 to 18.06 μg m−3. Finally, 11 main hazardous air pollutant VOCs, accounting for 32.77% of the TVOCs, were propylene, 2-butanone, toluene, methyl methacrylate, etc., with the concentration ranging from 81.05 to 116.96 μg m−3. Results could contribute to filling the knowledge gaps in the characteristics of VOC emissions from biogas digestate (BD), and provide a basis for exploring mitigation strategies on odor and hazardous air pollutions.

The modelling of odour dispersion as a support tool for the improvements of high odours impact plants

Two scenarios in terms of odour impact assessment were studied during the phase of upgrading of an existing waste treatment plant: CALPUFF was used for the simulation of odour dispersion. Olfactometric measures, carried out over different periods and different positions in the plant, were used for model calibration. Results from simulations were reported in terms of statistics of odour concentrations and isopleths maps of the 98th percentile of the hourly peak concentrations, as requested from the European legislation and standards. The excess perception thresholds and emissions were utilized to address the plant upgrade options. The hourly evaluation of odours was performed to determine the most impacting period of the day. An inverse application of the numerical simulation starting from defining the odour threshold at the receptor was made to allow the definition of the required abatement efficiency at the odours source location. Results from the proposed approach confirmed the likelihood to adopt odour dispersion modelling, not only in the authorization phase, but also as a tool for driving technical and managing actions in plant upgrade so to reduce impacts and improve the public acceptance. The upgrade actions in order to achieve the expected efficiency are reported as well.

Influence of activated carbon porosity and surface oxygen functionalities' presence on adsorption of acetonitrile as a simple polar volatile organic compound

Based on series of porous carbon models, systematic Monte Carlo studies on the adsorption of acetonitrile (as a simple representative of polar volatile organic compounds) were performed. The influence of porosity and chemical composition of the carbon surface on CH3CN adsorption was studied and it was shown that both the factors influenced the adsorption mechanism. A decrease in the pore size and the introduction of oxygen surface groups led to a rise in adsorption energy and to an increase in the filling of accessible volume in the low-pressure part of the isotherm. However, from a practical point of view, it is easier to increase the adsorption by introducing polar groups on the carbon surface than by modifying the porosity.