Page 388 - Materials Chemistry, Second Edition

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The Sanitary Landfill 359
To distribute evenly the waste accepted between 1957 and 1964, highlight the MSW in Place
cells for these years (i.e., highlight all cells between and including 1957 and 1964). Then choose
the Autocalc function from the Edit menu. The MSW data should be evenly distributed back to
1957. You should now observe as well that the MSW in Place value for the year 1995 is now
3,400,000 Mg, or half the landfill capacity.
From the Parameters menu, select the Closure Year item. Click the User Specified diamond and
enter 2010 in the adjacent box. Then choose the [OK] button. Once the closure year data have been
chosen, the scenario is complete, and the study can be run by generating a report. The software
model will automatically calculate the waste acceptance rates necessary to reach the landfill capac-
ity in the specified closure year.

QUESTIONS

To examine the landfill emissions calculated by the model, a report is generated. For this example,
the NMOC concentrations over the lifetime of the landfill is to be determined. From the Report
menu choose the Graphics option. When the Select an Emitted Substance dialog box opens, choose
NMOC and click the [OK] button. A new window displaying the graphical report will open. What
is the trend of NMOC concentrations over time? When does the peak in concentration occur? What
does this year coincide with?
Is it realistic to expect constant values of waste acceptance in a landfill serving urban and sub-
urban populations, including commercial establishments? What changes would you expect over the
course of 45 years in a landfill which serves your home community or university? Perform another
calculation on this same landfill, with the same capacity and the same annual acceptance rate; how-
ever, the landfill is now about 75% full. When will the landfill reach full capacity? What are the
methane generation rates?

PROBLEM

For a second landfill, less data are available. The capacity is 4,250,000 Mg and the landfill is
expected to operate for 40 years. For a case such as this, a Year Opened value of 1 and a Current
Year value of 41 can be used. The model will calculate the Closure Year automatically, and it will
be assumed that the waste is accepted at a uniform rate throughout the length of operation. This
study will be used to estimate the actual emissions by using the AP-42 default values for k and L ,
o
and the landfill will be assumed to accept both hazardous and nonhazardous waste (Co-disposal).
Select the AP-42 option from the Defaults menu, and in this situation, click on Co-disposal in
the Landfill Type item in the Parameters menu. The waste acceptance rates during the 50 years of
operation are assumed to be constant. Therefore, the waste should be evenly distributed over the life
of the landfill.
What is the annual rate of MSW acceptance?
Graph a report of NMOC generation. When do concentrations peak?

A.10.1.3 THE HYDROLOGIC EVALUATION OF LANDFILL PERFORMANCE MODEL

The Hydrologic Evaluation of Landfill Performance (HELP) model is a user-friendly computer
program that estimates water balances for municipal landfills and other land disposal systems. The
HELP model was developed at the U.S. Army Engineer Waterways Experiment Station in order to
assist landfill designers and environmental regulators in evaluating the hydrologic performance of
landfill designs. The use of this model allows engineers and regulatory personnel to compare dif-
ferent designs in efforts to construct an environmentally sound land disposal facility. The HELP
model is recommended by the U.S. EPA and required by most states for evaluating closure designs
of both municipal (RCRA Subtitle D) and hazardous (Subtitle C) waste management facilities.