74    TREATABILITY STUDY OF HIGH STRENGTH LANDFILL
LEACHATE
Anthony F. Gaudy, Jr., Professor
Alan F. Rozich, Associate Scientist
Stephanie Garniewski, Graduate Student
Department of Civil Engineering
University of Delaware
Newark, Delaware 19716
INTRODUCTION
The sanitary landfill was devised over four decades ago as a relatively inexpensive, hygienic way to
bury solid refuse rather than continue the then prevalent practice of open dumping. At the time little
consideration was given to the potential for groundwater pollution. The landfill is an attractive
technology because, in addition to its simplicity and relatively low cost, it is an ultimate method of
disposal (as, for example, compared to incineration of municipal refuse). As the use of this technique
grew, there was increasing concern over pollution of groundwater by organic materials leached from
the municipal refuse and, since many municipalities accepted industrial wastes as well as municipal
refuse, there was increasing concern over the possibilities for entry of hazardous waste components
into the groundwater resource. Today, mounting evidence for groundwater contamination mandates
that modern landfill design provide means for containing all seepage, or leachate, from the fill.
The sanitary landfill operated at Sandtown, Delaware, by the Delaware Solid Waste Authority is a
state-of-the-art facility in which leachate is collected and held on the site, but as yet there is no
provision for its treatment. The facility accepts solid industrial wastes as well as municipal refuse. The
operational and managerial strategies for the facility are presented elsewhere [1]. Approximately
25,000-30,000 gallons of leachate are produced daily. Its BOD5 is approximately 100 times higher
than that of municipal sewage and it contains significant amounts of heavy metals. Since the amenability of municipal landfill leachate to aerobic biological treatment has been rather widely reported
and, since some of the work recently reported from our bio-environmental engineering laboratories
has dealt with biological treatment of waste containing heavy metals [2,3] and inhibitory and toxic
compounds [4,5,6,7] as well as conventional pollutants, the Delaware Solid Waste Authority
approached us to discuss the possibilities for investigating the biological treatment of the Sandtown
site leachate. Our task was essentially three-fold.
There was need for additional information on the chemical characteristics of the leachate. The
Authority, from time to time, had obtained BOD, COD, and metals analyses on the waste, as well as
analyses for volatile acids concentrations, but a more systematic program of sampling and analysis
was needed to gain some idea of the variations in composition which might be expected, as well as the
average values.
Since it is widely known that leachate composition varies from site to site, it is equally well-
recognized that the amenability of the leachate to biological treatment can also vary. Thus, it was
important to perform a treatability investigation on the leachate over a period of time sufficient to
allow assessment of the biochemical response to variations which might occur in the waste composition. One of the best approaches to treatability studies which we have found is to determine values of
the biokinetic parameters which govern the process. These are also the kinetic characteristics needed
for insertion into kinetic models for prediction of performance and of the effects of variation in
engineering control parameters on system performance. That is, the study should include the determination of the following biokinetic "constants": ^max, the maximum specific growth rate; Ks, the
saturation constant; K,, the inhibition constant; kd, the specific decay rate; Yt, the true cell yield; and
ka, the autodigestion constant. In our view, such studies require the running of both a continuous-
flow pilot plant and batch experiments.
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