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The use of in-vessel composting as a treatment technology for hazardous waste minimization
ABSTRACTS
conductivity in an aquifer on the ability to supply microorganisms with oxygen and nutrients. Scenarios for bioremediation in an aquifer and in a pond will be studied in quantifying such sources of variability. The third objective will be to apply the data obtained on the variability of bioremediation to develop a stochastic description of the parameters in the stochastic bioremediation model. The fourth objective will be to combine the bioremediation model with the risk assessment model. The bioremediation model will then be able to provide information on the variability of the contaminant concentration distribution so that the risk assessment model can calculate the distribution of expected risks and how they change during remediation. The last objective will be to use the model to characterize how bioremediation processes reduce risk. Sensitivity analysis will be conducted to determine the major sources of variability in risk calculations.
THE USE OF IN-VESSEL COMPOSTING AS A TREATMENT TECHNOLOGY FOR HAZARDOUS WASTE MINIMIZATION K. W. B r o w n Soil and Crop Sciences Department, Texas A & M University, College Station, Texas 77843-2474, U.S.A.
Increasingly, stringent governmental regulations controlling the land disposal of hazardous wastes have created a need to develop new technologies for waste treatment to minimize the concentrations of hazardous constituents prior to disposal. Advances in municipal sewage sludge disposal technologies have resulted in the development of in-vessel composting technology. The present study was designed to evaluate the potential use of in-vessel composting for the treatment of hazardous waste streams containing representative hazardous organic contaminants. Information is available for past studies on the optimum operating conditions for in-vessel composting, such as the type of bulking agent, porosity, C:N:P ratio, moisture content, and oxygen supply. Other researchers have documented the biodegradability of many hazardous organic components of oily and other wastes. What has been missing is clear documentation of the fate of these waste components as the waste is treated by in-vessel cornposting.
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The present study is designed to provide data on the fate of selected organic compounds as a hazardous organic waste stream, such as API separator sludge or a pesticide, undergoes in-vessel composting. A mass balance of the amounts volatilized, degraded, or remaining unchanged of six toxic compounds is being maintained. The data provided by this study can be used by the petroleum industry, those faced with cleaning up Superfund sites,and others to design and operate in-vessel composting systems for hazardous waste treatment. Six laboratory scale in-vessel composters were designed from four cubic foot cement mixers by modifying them to provide uniform mixing and aeration, as well as easy access to the interior. Intermittently during the composting cycle the waste mixture is sampled and analyzed for the amount of original compound remaining. Because the composters are air-tight, the existing air stream is passed through a carbon filter to trap any volatilized compounds. The difference between the initial amount of compound and the amounts measured to be volatilized from or remaining in the waste mixture is representative of the amount of compound degraded by the in-vessel composting process. Several experiments were run using different amounts of hazardous waste and different amounts of spiked compounds, as well as controls. Preliminary results indicate that under optimal composting conditions, a minimum of compound is lost by volatilization, with the majority of volatilization occurring within the first 3-4 days. As the percentage of spiked toxic compounds increases above a threshold level, the efficiency of the composting process is lowered such that as much as 50% of certain compounds is lost due to volatilization. Because experiments using equal amounts of hazardous waste with lower levels of spiked chemicals do not indicate a loss of composting efficiency when compared with the similar experiments at high spiked compound concentrations, the efficiency loss is attributed to microbial toxicity, and not to sub-optimal composting conditions, such as porosity, aeration, or nutrient levels. GUIDED WAVE OPTICAL SENSOR FOR TRACE-LEVEL HAZARDOUS SUBSTANCES Bruce Buckman Electrical & Computer Engineering, ENS 143, University of Texas at Austin, Austin, Texas 78712, U.S.A.
conductivity in an aquifer on the ability to supply microorganisms with oxygen and nutrients. Scenarios for bioremediation in an aquifer and in a pond will be studied in quantifying such sources of variability. The third objective will be to apply the data obtained on the variability of bioremediation to develop a stochastic description of the parameters in the stochastic bioremediation model. The fourth objective will be to combine the bioremediation model with the risk assessment model. The bioremediation model will then be able to provide information on the variability of the contaminant concentration distribution so that the risk assessment model can calculate the distribution of expected risks and how they change during remediation. The last objective will be to use the model to characterize how bioremediation processes reduce risk. Sensitivity analysis will be conducted to determine the major sources of variability in risk calculations.
THE USE OF IN-VESSEL COMPOSTING AS A TREATMENT TECHNOLOGY FOR HAZARDOUS WASTE MINIMIZATION K. W. B r o w n Soil and Crop Sciences Department, Texas A & M University, College Station, Texas 77843-2474, U.S.A.
Increasingly, stringent governmental regulations controlling the land disposal of hazardous wastes have created a need to develop new technologies for waste treatment to minimize the concentrations of hazardous constituents prior to disposal. Advances in municipal sewage sludge disposal technologies have resulted in the development of in-vessel composting technology. The present study was designed to evaluate the potential use of in-vessel composting for the treatment of hazardous waste streams containing representative hazardous organic contaminants. Information is available for past studies on the optimum operating conditions for in-vessel composting, such as the type of bulking agent, porosity, C:N:P ratio, moisture content, and oxygen supply. Other researchers have documented the biodegradability of many hazardous organic components of oily and other wastes. What has been missing is clear documentation of the fate of these waste components as the waste is treated by in-vessel cornposting.
343
The present study is designed to provide data on the fate of selected organic compounds as a hazardous organic waste stream, such as API separator sludge or a pesticide, undergoes in-vessel composting. A mass balance of the amounts volatilized, degraded, or remaining unchanged of six toxic compounds is being maintained. The data provided by this study can be used by the petroleum industry, those faced with cleaning up Superfund sites,and others to design and operate in-vessel composting systems for hazardous waste treatment. Six laboratory scale in-vessel composters were designed from four cubic foot cement mixers by modifying them to provide uniform mixing and aeration, as well as easy access to the interior. Intermittently during the composting cycle the waste mixture is sampled and analyzed for the amount of original compound remaining. Because the composters are air-tight, the existing air stream is passed through a carbon filter to trap any volatilized compounds. The difference between the initial amount of compound and the amounts measured to be volatilized from or remaining in the waste mixture is representative of the amount of compound degraded by the in-vessel composting process. Several experiments were run using different amounts of hazardous waste and different amounts of spiked compounds, as well as controls. Preliminary results indicate that under optimal composting conditions, a minimum of compound is lost by volatilization, with the majority of volatilization occurring within the first 3-4 days. As the percentage of spiked toxic compounds increases above a threshold level, the efficiency of the composting process is lowered such that as much as 50% of certain compounds is lost due to volatilization. Because experiments using equal amounts of hazardous waste with lower levels of spiked chemicals do not indicate a loss of composting efficiency when compared with the similar experiments at high spiked compound concentrations, the efficiency loss is attributed to microbial toxicity, and not to sub-optimal composting conditions, such as porosity, aeration, or nutrient levels. GUIDED WAVE OPTICAL SENSOR FOR TRACE-LEVEL HAZARDOUS SUBSTANCES Bruce Buckman Electrical & Computer Engineering, ENS 143, University of Texas at Austin, Austin, Texas 78712, U.S.A.