82    PHYSICAL/CHEMICAL TREATMENT OF SANITARY
LANDFILL LEACHATE
Riley N. Kinman, Professor
Department of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221
David L. Nutini, General Manager
RNK Environmental, Inc.
Covington, Kentucky 41017
INTRODUCTION
Sanitary landfill leachate is one of the most difficult waste streams to treat in a reasonable and cost
effective manner.1 Onsite treatment to meet an NPDES permit requirements necessitates a complex
treatment plant to handle the variability of flow and pollutant concentrations. Since leachate flow is a
function of water infiltration reaching the landfilled municipal solid waste (MSW), quantity of
leachate to be treated is usually questionable and highly variable from maximum flow to minimum
flow. In like manner many of the pollutants in the leachate have been washed from the landfilled
MSW and will vary significantly in concentration. COD might range from 10,000 mg/L or so to
90,000 mg/L. Table I2 contains some of the pollutant concentrations observed in sanitary landfill
leachate.
Leachate volume variability and strength variability usually dictates that the best over-all treatment
scheme is treatment off-site by a municipal POTW. This allows equalization of the flow and strength
of the leachate and provides a mix with domestic wastewater that is much more amenable to treatment
on a consistent basis. Usually, some type of pretreatment is provided before discharge to a municipal
sewer system. This is the situation in this case. Pretreatment by aeration provided by two blowers and
a submerged diffused air header system in a concrete (30,000 gal) aeration tank.
The objectives of this study were to evaluate physical/chemical treatment of the leachate in case the
POTW changed the permit requirements for the quality of the leachate being discharged to its system.
Specifically, high lime dose with Ca(OH)2, alkaline permanganate treatment with KMn04, and hydrogen peroxide treatment with H202 were tried to reduce BOD5, COD, and other pollutants.
SITE CHARACTERIZATION
Figure 1 is a schematic of the landfill and leachate production and collection system. Leachate is
generated from the disposal of MSW for over 40 years. The landfill has an expected life of about 13
more years when a new section of the sanitary landfill is permitted. Leachate is picked up by a
leachate collection system and pumped by two 200 gpm centrifugal pumps up to the aeration tank. Air
is delivered to the leachate by a standard (sewage treatment system) blower and diffused air system
which has submerged stainless steel headers with porcelain diffusers. Runoff from a truck wash pad,
sanitary waste from a shop building and gas recovery plant flow by gravity to a pond. This pond water
is pumped into the aeration tank also for pretreatment. Pretreated leachate (methane gases, hydrogen
sulfide, and other volatiles are stripped by the aeration process) is pumped about 3 miles through an
8" force main (PVC) to a gravity sewer owned by the local MSD. The pretreatment leachate flows by
gravity, after mixing with domestic sewage, to a large conventional activated sludge treatment plant
for final treatment. Landfill gas recovery plant condensate is added after the leachate is pretreated
and before the leachate reaches the sanitary sewer. Total flow of leachate may be as high as 100,000
gallons per day. Usually the flow is much less than this, in the 30,000 to 60,000 gallons per day range.
Flow is a function of rainfall and infiltration into the sanitary landfill and hence, to the leachate
collection system.
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea. Michigan 48118.
Printed in U.S.A.
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