A model for determining the fate of hazardous constituents in waste during in-vessel composting

Abstract

Composting is one of the techniques that has evolved as a safe disposal and predisposal alternative to the stringent regulations on hazardous waste disposal. The implementation of this technique needs careful evaluation of the processes a hazardous compound undergoes when subjected to composting. The purpose of this thesis is to define these processes and develop a model for determining the fate of organic compounds in waste during in-vessel composting Volatilization and biodegradation are found to be the major fate determining processes. Following mass balance approach the compound's loss through these processes is evaluated by developing a fate model. Fate of six aromatic compounds which fall into three categories-volatile, semi-volatile, and non volatile, is determined and the results compared to the experimental values for validating the model. A sensitivity analysis has been performed to determine which parameters most influence the model behavior and quantitatively describe their effects on model performance. The results obtained from the model show close agreement with the experimental results. More data is required to quantify the slight differences observed. The volatilization loss is found to exist only for first few hours. Biodegradation rates are found to have very little impact on volatilization of the compound. Air flow rate and volume of the waste are found to have a noticeable effect on the volatilization of a compound. Bulk density is found to effect volatilization to a small extent. Air quality control measures are recommended for the first few days to deal with the volatilized gases.