A NEW TYPE OF ANAEROBIC DESIGN
FOR ENERGY RECOVERY AND
TREATMENT OF LEACHATE WASTES
J. L. Carter, Process Engineer
G. M. Curran, Project Engineer
P. E. Schafer, Project Manager
Black and Veatch, Engineers-Architects
Kansas City, Missouri 64114
R. T. Janeshek, Technical Manager
G. C. Woelfel, Regional Engineer
Waste Management, Inc.
Milwaukee, Wisconsin 53222
DESCRIPTION OF OMEGA HILLS LANDFILL AND OPERATION
The Omega Hills landfill, operated by Waste Management, Inc. (WMI), is located 15 miles northwest of downtown Milwaukee, Wisconsin. The landfill accepts municipal, industrial, and commercial wastes at daily rates ranging from 5,000 to 10,000 gate cubic yards per day. In the past, the 83 acre
landfill accepted liquids and sludges for co-disposal, utilizing the absorptive capacity of the refuse.
Approximately 1 million cubic feet of gas is burned at the landfill daily. The methane content of the
gas produced is approximately 58 percent and pressures as high as 1 psi have been recorded.
Some areas of the landfill are provided with leachate collection systems consisting of base laterals
leading to extraction risers or manholes. Waste Management is currently extracting leachate from
these systems; in addition, it has developed and implemented supplemental leachate extraction utilizing vertical caissons drilled to the base of the site and equipped with well screens and automatic extraction pumps. Leachate withdrawn from the landfill is pumped to 5,500 gallon tank trucks and
discharged through a drop inlet to a sewer leading to the Milwaukee Metropolitan Sewerage District
(MMSD) South Shore Treatment Plant.
The Wisconsin Department of Natural Resources (WDNR) has requested that WMI provide a
treatment system for the leachate by the fall of 1984. A bench scale study by Rexnord, Inc., dated
March 30, 1982 showed that the leachate could be treated by anaerobic digestion. In January 1983,
WMI requested Black & Veatch to do the engineering work for the treatment plant.
WASTE CHARACTERISTICS
Although there are wide variations in the Omega Hills leachate characteristics, representative
leachate has the characteristics shown in Table I. Heavy metals are present; however, zinc is the only
metal in sufficient concentration to potentially inhibit anaerobic activity. The Rexnord study showed
that phosphorus was limiting and would have to be added for any significant biological treatment to
occur.
DESIGN CONSIDERATIONS
The history of anaerobic treatment and a review of different types of anaerobic reactors has been
presented by McCarty [1]. Mosey reviewed anaerobic filter concepts and described results of treating
carbohydrate wastes [2]. His evaluation and comparison of data is especially useful. Curves are given
showing the relationship between organic loading and COD removal. Dague also discussed the prin-
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