24    PRELIMINARY ASSESSMENT OF A
MICROFILTRAITON/REVERSE OSMOSIS
PROCESS FOR THE TREATMENT OF LANDFILL
LEACHATE
Thomas A. Krug, Process Engineer
Sandra McDougall, Engineer
ZENON Environmental, Inc.
Burlington, Ontario
CANADA L7N 3P3
INTRODUCTION AND BACKGROUND
In recent years, the occurrence of a wide variety of organic and inorganic contaminants in ground
and surface water has become recognized as a significant environmental concern by regulatory agencies. Toxic and hazardous compounds can originate from landfill leachates as a result of the soluble
components of solid and liquid wastes being leached into surface and groundwater.
Often these landfill leaches are comparable to complex industrial waste streams which contain both
toxic organic and inorganic contaminants. In cases where drinking water supplies may be impacted or
where there is surface breakout, remedial actions must be undertaken. At some landfill sites leachate
which is collected is discharged to municipal sewers for treatment in conventional sewage treatment
processes. At other landfill sites where sewer lines are not available the leachate water may be hauled
off site for treatment, may be recycled back to the landfill site or may be discharged to a surface water
source. Hauling leachate for treatment by conventional processes is expensive and new regulations
may limit the discharge of such complex wastes to municipal sewers since the nature of the contaminants are often not appropriate for treatment in conventional municipal biological processes. Recycling leachate within the landfill site itself can reduce the amount of liquid leaving the site but can only
provide a short term solution. Effective and inexpensive methods of treating the material need to be
developed.
Cross flow filtration processes including microfiltration (MF), ultrafiltration (UF) and reverse
osmosis (RO) have been applied to the treatment of a wide variety of industrial waste water streams.
Microfiltration processes with a filtration size of 0.1 to 1.0 microns remove suspended solids which
are not easily settled and have been applied to the treatment of many wastewaters. In particular they
have been successfully employed in the treatment of metal contaminated wastewater as the solids
removal step after chemical precipitation of toxic metals. The MF process provides assured discharge
water quality and is less susceptible to upset conditions than conventional solids removal processes.
Ultrafiltration processes which operate in a smaller filtration range (0.002-0.1 microns) are commonly used for the concentration of wastewater containing emulsified oils or large molecular weight
organic contaminants.
Reverse Osmosis processes with a filtration range of less than 0.002 microns are used for the
removal of dissolved solids and organic contaminants. Considerable work has been done evaluating
the use of RO for the removal of problematic compounds in a variety of waste streams. Some of these
include wastewater from electroplating, petroleum, petrochemical, pulp and paper and food processing plants. Researchers have also investigated the possibility of using reverse osmosis for the treatment
of landfill leachates.
Chian and DeWalle1 of the University of Illinois studied leachate characteristics and related these
findings to the most effective treatment method to utilize. Data analysis of the ratios of parameters
such as BOD/COD and COD/TOC revealed that the leachate from young landfills containing mainly
free volatile fatty acids can be degraded by biological means whereas old fills containing refractory
organics were more effectively treated using physical/chemical methods. They also concluded that of
all physical/chemical methods evaluated reverse osmosis membrane treatment was the most effective
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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