Section Ten
INDUSTRIAL WASTE CASE HISTORIES
68    HORIZONTAL INJECTION LEACHATE RECYCLE:
CONSTRUCTION-OPERATION GUIDELINES AND
DESIGN PROCEDURE
Timothy G. Townsend, Post-Doctoral Associate
W. Lamar Miller, Professor
Department of Environmental Engineering Sciences
University of Florida
Gainesville, Florida 32611
INTRODUCTION
This paper outlines guidelines for the design, construction, and operation of horizontal injection leachate recycle systems (HI-LRS) at solid waste landfills. Horizontal injection leachate recycle is a method to recirculate collected landfill leachate back through landfilled material using
horizontal wells buried within the waste. Leachate recycle offers the potential to accelerate the
decomposition of biodegradable components in the landfill, to provide some measure of leachate
treatment, and to provide a method of leachate volume management.
The information presented is derived from three years of work in the construction and operation of a HI-LRS at a Florida landfill and an analysis of theoretical relationships of steady-state
saturated flow from a horizontal injection well. The details of this work—including a site description, methodology, and results—have been presented elsewhere.1 The design guidelines presented here apply to the sizing and placement of the landfill's hydraulic structures, specifically
the LRS pumping and conveyance system, the injection lines, and the leachate collection system.
Other landfill aspects not considered here, but which play a potential role in the design of such a
system include the effect of leachate recycle application rates and frequency on the landfill decomposition process, the effect of the HI-LRS on the overall hydrologic balance at the site, and
the collection of landfill gas from the injection lines. This paper is intended to provide fundamental information for the implementation of HI-LRS at solid waste landfills.
THEORY OF HORIZONTAL INJECTION
The principles behind the leachate recycle process have been well illustrated in pilot-scale
work2-3 and have been applied at numerous full-scale sites in the United States and throughout
the world.4-5 A variety of leachate recycle methods have been employed, each with distinct advantages and disadvantages. One method which possesses a number of advantages over other
leachate recycle methods is horizontal injection. This technology utilizes perforated pipe or
drainage material placed in horizontal trenches buried within the landfill waste. The trenches are
constructed during the operational years of the landfill while waste is deposited.
A HI-LRS permits the recirculation of leachate to the interior of the landfill without exposure
to the atmosphere. Leachate may be gravity fed or pumped under pressure. Placement of injection wells at different locations and elevations allows control of the rate and frequency of
leachate application to areas within the landfill. Horizontal injection wells present minimal interference with landfill surface operations and vehicle traffic.
50th Purdue Industrial Waste Conference Proceedings, 1995, Ann Arbor Press, Inc.. Chelsea, Michigan 48118.
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