ABSTRACT
UNLABELLED: Composting is widely used for the treatment of solid organic wastes; however emissions from composting are becoming a threat to humans due to the release of toxic volatile organic compounds (VOCs). VOCs from composting operations are characterized by high flow rates and, normally, low pollutant concentration. Typical VOCs include a large amount of terpenes (-65% of total VOCs). This study was to investigate the efficiency of biofiltration in controlling terpene emissions from composting operations using a laboratory-scale unit. The performance of a biofilter was investigated as a function of inlet flow rate, inlet concentration, and bed length/bed diameter (L/D) ratio of bed. At the lowest total inlet flow rate, removal efficiency of limonene and beta-pinene was more than 90%. With the decrease in inlet concentration and increase in L/D ratio, the removal efficiency was effectively increased. Removal efficiency of more than 85% for Limonene and 45% for beta-Pinene was attained at a loading rate of 55 g/m3-hr. The maximum elimination capacity was found for 109.7 g/m3-hr for limonene and 10.3 g/m3-hr for beta-pinene at a critical loading of 150.1 g/m3-hr Based on this study, the compost bed could function as a biofilter for controlling terpene odors during the composting process. IMPLICATIONS: The purpose of this research project is to investigate the efficiency of biofiltration in controlling limonene and beta-pinene emissions from composting operations using a laboratory scale. In addition, the performance of a biofilter as a function of inlet flow rate, inlet concentration, and L/D ratio of bed was evaluated. Establishing a nexus between the operational parameters and efficiency would be useful in design and operation of compost bed as a biofilter for controlling terpene odors during the composting process.
Subject(s)
Bridged Bicyclo Compounds/isolation & purification , Cyclohexenes/isolation & purification , Filtration/methods , Monoterpenes/isolation & purification , Terpenes/isolation & purification , Waste Management/methods , Bicyclic Monoterpenes , Environmental Restoration and Remediation , Limonene , Soil , Volatile Organic Compounds/isolation & purificationABSTRACT
Optimization of the simultaneous chemical and biological mineralization of perchloroethylene (PCE) by modified Fenton's reagent and Xanthobacter flavus was investigated by using a central composite rotatable experimental design. Concentrations of PCE, hydrogen peroxide, and ferrous iron and the microbial cell number were set as variables. Percent mineralization of PCE to CO2 was investigated as a response. A second-order, quadratic response surface model was generated and fit the data adequately, with a correlation coefficient of 0.72. Analysis of the results showed that the PCE concentration had no significant effect within the tested boundaries of the model, while the other variables, hydrogen peroxide and iron concentrations and cell number, were significant at alpha = 0.05 for the mineralization of PCE. The 14C radiotracer studies showed that the simultaneous chemical and biological reactions increased the extent of mineralization of PCE by more than 10% over stand-alone Fenton reactions.
Subject(s)
Ferrous Compounds/metabolism , Gram-Negative Aerobic Bacteria/metabolism , Hydrogen Peroxide/metabolism , Tetrachloroethylene/chemistry , Tetrachloroethylene/metabolism , Biodegradation, Environmental , Carbon Dioxide/metabolism , Gram-Negative Aerobic Bacteria/growth & development , Models, Biological , Regression AnalysisABSTRACT
The toxic effects of modified Fenton reactions on Xanthobacter flavus FB71, measured as microbial survival rates, were determined as part of an investigation of simultaneous abiotic and biotic oxidations of xenobiotic chemicals. A central composite, rotatable experimental design was developed to study the survival rates of X. flavus under various concentrations of hydrogen peroxide and iron(II) and at different initial cell populations. A model based on the experimental results, relating microorganism survival to the variables of peroxide, iron, and cellular concentrations was formulated and fit the data reasonably well, with a coefficient of determination of 0.76. The results of this study indicate that the use of simultaneous abiotic and biotic processes for the treatment of xenobiotic compounds may be possible.
