Section Four
WASTE MANAGEMENT
C. LEACHATE TREATMENT
27    USE OF OZONE AND ULTRAVIOLET OXIDATION TO
ENHANCE THE BIOLOGICAL DEGRADATION OF
REFRACTORY ORGANICS IN LANDFILL LEACHATE
Linda Fazzini, Environmental Engineer
Boeing Defense & Space Group
Philadelphia, Pennsylvania 19142
James C. Young, Kappe Professor
Environmental Engineering
The Pennsylvania State University
University Park, Pennsylvania 16802
INTRODUCTION
Biological processes are commonly used to treat leachates from landfills across the United States,
but experience has shown that it is not always possible to reduce the chemical oxygen demand (COD)
to the desired limit. As the age and conditions of a landfill change, so do the characteristics of the
leachate.1"3 Treatment techniques that might have been effective in the early stages in the life of a
landfill may no longer be applicable to leachate that is generated years later.
The composition of a landfill leachate determines its relative treatability. Organic composition
changes over time as the landfill moves through different phases of decomposition. During the first,
or aerobic, phase oxygen and nitrate are consumed by microorganisms that biodegrade soluble sugars.
This step is followed by the second, or anaerobic fermentation, phase in which bacteria degrade
complex organic compounds and generate soluble organic acids, amino acids and other low molecular
weight compounds. At this point, the organic content of the leachate consists mainly of volatile fatty
acids (VFA) such as acetic, propionic, butyric, isobutyric, valeric, isovaleric, and hexanoic acids.4"7
The third, or methanogenic, phase takes over as anaerobic bacteria begin to dominate and utilize the
organic acids to produce methane (CH4) and carbon dioxide (C02). As the landfill stabilizes, the
anaerobic microorganisms consume the more easily degradable compounds.5 The organic compounds
found in the resulting leachate are higher molecular weight compounds including humic and fulvic
acids.
The authors' study was designed to evaluate the use of 03/UV as a potential process for cracking
the refractory organic compounds in a landfill leachate, thus making them more amenable to biological degradation. This use of advanced oxidation seems to be an attractive alternative for several
reasons. First, by exposing the waste to 03/UV, the refractory compounds can be oxidized to form
biodegradable products, thereby allowing more effective biological treatment.9"" Second, 03/UV
treatment is also appealing at a time when waste minimization is important. Rather than removing the
refractory portion by using a method that only transfers the contaminants from one phase to another,
such as chemical precipitation or reverse osmosis, oxidation provides a means of destroying the
organic compounds or altering them to enable more complete biological degradation.
Specifically, the objectives of this study were to:
1. Compare the effectiveness of 03 and UV alone and in combination in reducing COD
and total organic carbon (TOC).
2. Determine the effect of increasing ozone dosage and contact time.
3. Examine the effect of 03/UV on the overall biodegradability of the organic constituents
in landfill leachate.
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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