KINETICS FOR BIODEGRADATION OF POLYCYCLIC AROMATIC HYDROCARBONS

A laboratory-scale batch type in-vessel composter was charged with simulated municipal solid waste deliberately contaminated with a mixture of three- and four-ringed polycyclic aromatic hydrocarbons (PAHs). There were two distinct physical phases of this experiment: the active composting and the curing phase. The extent of their biodegradation was monitored over a two month time period (30 days of active composting and 30 days of compost curing) using soxhlet extraction and gas chromatography analysis. The results indicated that most of the biodegradation occurred in the active composting phase and very little occurred during the curing phase of the composting process. Benz[a]anthracene was persistent in the compost throughout both phases of the experiment. Anthracene, phenanthrene, and pyrene showed excellent reduction in the active compost phase, in contrast to the mercuric chloride poisoned control, indicating that biodegradation (not abiotic mechanisms) was the removal process. Kinetic analysis of the results determined that the rate of biodegradation of the PAHs was pseudo first order. For kinetic analysis, the active composting phase was further subdivided into subphase I (days 0-15) and subphase II (days 15-30). Most of the biodegradation occurred during subphase I of the active composting phase. Biodegradation of all three- and four-ringed PAHs did occur; however, only anthracene, phenanthrene, and pyrene are ideal for biodegradation.