Treatability of Leachate from Sanitary Landfills
W. C. BOYLE
R. K. HAM
Department of Civil and Environmental Engineering
The University of Wisconsin
Madison, Wisconsin
INTRODUCTION
Before 1965 very few people were aware of the fact that water passing through refuse in
a landfill would become highly contaminated. This water, hereafter termed leachate, was
generally not a matter of concern because few cases were noted where leachate had caused
harm to someone. With the recent popularity of environmental matters, however, the
importance of leachate as a particularly undesirable aspect of solid waste disposal on land
has risen to the point that disposal sites are usually chosen to minimize the hazard
associated with leachate. Furthermore, it is not uncommon to hear of cases where sites
which might otherwise give rise to leachate problems are being used, with the provision that
any leachate generated is collected and disposed of in some harmless fashion. Implicit in this
provision is the assumption that, once leachate has been collected, there are proven
methods whereby it may be treated or safely sent into the environment. It appears that this
assumption is not valid, however, for little information is in the literature on the subject
and, in cases where leachate is being collected, treatment is non-existent or rudimentary due
to the lack of a proven method. The purpose of the work described in this paper is to
evaluate a variety of leachate treatment schemes, developing design and operating criteria
for the most promising ones.
Two general categories of treatment processes would be useful for leachate treatment:
those which would be used if only leachate were to be treated, and those which could be used
as pretreatment systems prior to final processing in a sewage treatment plant. The first
category of processes would be suitable if leachate were being generated at a location
remote from sanitary sewer service. The most useful processes in such a situation are those
which can be operated with a minimum of supervision and are either inexpensive to
construct or are readily moved from one site to the next. Processes considered for the
second category, where access to a sewage treatment plant is available, should complement
the removals obtained by the treatment plant, and should provide sufficient pretreatment to
insure that the efficiency of sewage treatment is not impaired.
The studies described in this paper were designed to evaluate in the laboratory the
ability of a variety of individual treatment processes to treat leachate. Processes evaluated
include anaerobic and aerobic biological treatment of leachate; aerobic treatment of
selected combinations of leachate and domestic wastewater in a simulated activated sludge
sewage treatment plant; anaerobic followed by aerobic polishing treatment of leachate; and
chemical precipitation, oxidation, and coagulation.
DESCRIPTION OF LEACHATE TREATED
One of the most difficult aspects of a study involved with leachate treatment is
attempting to define the characteristics of the leachate to be treated. The literature is
beginning to provide descriptions of leachate collected under a variety of conditions in
several places around the country. For example, Table I provides composition data for
several leachates. Note the wide range in compositions observed in just these few examples,
and the extremely high concentrations of chemically diverse contaminants which may be
present. It is apparent that leachate quality varies so widely that attempts to define a typical
composition must include such broad concentration ranges ofthe various contaminants as
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