23    EVALUATION OF LEACHATE MONITORING DATA FROM
CO-DISPOSAL, HAZARDOUS, AND SANITARY WASTE
DISPOSAL FACILITIES
Audrey D. Levine, Assistant Professor
Liane R. Rear, Graduate Research Assistant
Department of Civil and Construction Engineering
Iowa State University,
Ames, Iowa 50011
INTRODUCTION
Monitoring of hazardous wastes, landfill leachates, and ground and surface water contamination is
a necessary component of hazardous waste management, treatment, and clean-up programs. Because
contaminants are measured in concentrations as low as parts per billion (ppb) or parts per trillion
(ppt), the test methods must be quite sensitive. Unfortunately, measurement techniques that can
detect trace levels of contaminants are subject to interferences from dissolved inorganic and organic
compounds present in leachates. Also, the expense of analytical testing often precludes the possibility
of conducting replicate analyses. Consequently, regulatory and management decisions are based on
limited sample analyses.
The selection of parameters and the frequency of monitoring is dependent on site-specific characteristics, disposal practices, and RCRA or CERCLA requirements.1 The parameters monitored may
include indicator parameters, conventional parameters, water quality parameters, or specific analyses
of over 300 organic and inorganic chemicals.2
Indicator, or surrogate, parameters are used as screening tests to identify the presence of toxic
compounds and determine the need for more extensive monitoring. Indicators of contamination
include total organic carbon (TOC), total organic halide (TOX), specific conductivity, and pH. In
practice, interpretation of monitoring results is difficult because all parameters do not necessarily
vary in the same way. An example of the variation of indicator parameters with time is shown in
Figure 1. On the basis of data presented for this site, it is difficult to evaluate temporal changes in
contamination levels.
As a result of monitoring programs currently in place, a wealth of information is currently available
on the concentrations of the indicator parameters and other organic and inorganic contaminants
present in leachates from various types of facilities. Evaluation of analytical results contained in
existing data bases is valuable for testing the effectiveness of monitoring procedures and for developing statistical models.
The objectives of this chapter are: 1) to identify significant differences in the characteristics of co-
disposal, hazardous, and sanitary landfill leachates; and 2) to evaluate the effectiveness of nonspecific
tests to detect toxic contaminants in leachates.
BACKGROUND
In the absence of information on specific contaminants the use of surrogate parameters is necessary
for identification of potential contamination sites. Ideally, the surrogate parameter should be present
at levels higher than background levels, easily measured, and subject to few interferents.
Surrogate parameters for inorganic constituents include specific conductance and pH. Surrogate
parameters used for detection of organic contamination are TOC and TOX.
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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