16    BIODEGRADATION POTENTIAL OF
ALKYLBENZENES AND PHENOLS IN LANDFILLS
Yu-Sheng Wang, Doctoral Candidate
Morton A. Barlaz, Associate Professor
Department of Civil Engineering
North Carolina State University
P.O. Box 7908, Raleigh, North Carolina 27695
ABSTRACT
This research evaluated the anaerobic biodegradability of benzene, toluene, yethylbenzene,
xylenes (BTEX), phenol, and p-cresol using microbial consortia derived from decomposing
refuse samples. The effects of environmental conditions, pertinent to landfills, on phenol and p-
cresol degradation were also studied. This study demonstrated that landfills harbor anaerobic microorganisms capable of degrading toluene, phenol, and p-cresol. In one consortium, phenol
biodegradation was stimulated by both cellulose and nutrient additions and degradation was optimal at pH 6.5 to 7.0. An accumulation of the fermentation intermediates, benzoate and acetate,
inhibited phenol biodegradation. The results show that it is possible to design landfill management strategies to promote contaminant biodegradation.
INTRODUCTION
Prior to 1980, there were few restrictions on the types and quantities of industrial waste buried
with municipal solid waste (MSW) in landfills. As a result of past waste disposal practices,
groundwater downgradient of uncontrolled landfills is frequently contaminated by leachate and
poses environmental hazards. Thus, it is not surprising that approximately 25% of the sites on
the EPA's National Priorities List of cleanup sites are landfills that accepted both hazardous and
municipal solid wastes.1 Benzene, toluene, ethylbenzene, xylenes (BTEX) and phenolic compounds are among the more common contaminants in landfill leachate.2-3 Benzene, as well as
several substituted phenols, including chlorophenols and cresols, are designated priority pollutants by the USEPA.
Landfills represent an active anaerobic ecosystem in which the conversion of cellulosic substrates to methane and carbon dioxide is well documented.4 The long residence time of refuse
buried in landfills enhances the opportunity for microbial degradation of recalcitrant compounds.
However, there has been only limited research on the fate of trace organic pollutants in landfills.
BTEX has been shown to biodegrade under denitrifying, sulfate-reducing, and methanogenic
conditions in habitats that include soil, aquifer sediment, and wastewater treatment sludge.5-7
However, to our knowledge the only research regarding BTEX in landfills was conducted by
Cossu and Serra (1989)8 who showed that the co-disposal of BTEX bearing sludge was not inhibitory to refuse methanogenesis. BTEX biodegradation was not documented.
Similarly, there has been only limited research on the biodegradation of phenols in the landfill
ecosystem.9 Reinhart and Pohland (1991)10 reported on the attenuation of some priority pollutants, including two phenolic compounds, using a laboratory-scale refuse column. The importance of biological processes to compound attenuation was not specifically addressed in their
study. Watson-Craik and Senior (1989)11 have reported phenol biodegradation in refuse columns
operated with leachate recycle. Anaerobic degradation of o-cresol was also measured by microbial consortia enriched from refuse.12
52nd Purdue Industrial Waste Conference Proceedings, 1997, Ann Arbor Press. Chelsea, Michigan 48118. Printed in
U.S.A.
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