AREA A/B ENGINEERING REPORT - Waste Management

Geosyntec Consultants
(infiltration) or injection trenches, or horizontal injection blankets. Currently, subsurface horizontal
infiltration trenches are the most common method used. Achieving an even distribution of moisture
throughout the waste mass is the most important operational factor as this avoids potential
problems with leachate seeps and lateral breakouts.
Based on the various site conditions and surrounding land uses, an effective and
long-term LMS can be variable and include different system features. Prior to
generating a reasonable design for the LMS, several questions need to be
answered:
• Is leachate recirculation planned (e.g., to enhance degradation of the waste, maximize
landfill gas generation, and develop “green energy” through methane collection and
conversion to electricity)?
• Is there a POTW located near the landfill that is permitted to accept leachate, or are only
on-site treatment options available?
• If only on-site options are available, is pre-treatment required prior to discharge, or is reintroduction
back into the waste mass preferable?
• Are nearby wetlands available that could be used for natural treatment of the leachate?
The answers to these and other questions will influence the final LMS design at the managed
landfill. If on-site treatment is selected as part of the LMS, there are a number of widely
adopted options for treatment of leachate, used either alone or in combination. The treatment
options can be divided into three general categories:
• Physical treatment, including evaporation/concentration, solids removal (e.g.,
sedimentation/settlement, filtration, or air flotation), and specialized techniques (e.g., air
stripping, activated carbon adsorption, ion exchange, or reverse osmosis);
• Chemical treatment, including chemical oxidation, precipitation, coagulation, and
flocculation; and
• Biological treatment, including aerobic (i.e., “with air”) systems such as aerated lagoons,
sequencing batch reactors (SBRs), membrane bioreactors (MBRs), and percolating filters;
anaerobic (i.e., “without air”) systems such as digesters and sludge blankets; and
combined aerobic/anaerobic systems such as engineered wetlands.
Use of these technologies for leachate treatment is based upon well documented success in
treating municipal and industrial wastewaters similar in characteristics to solid waste landfill
leachate. In many instances, effective treatment of landfill leachate may involve the adoption of
more than one treatment process. A site-specific treatment plan may involve the use of primary,
MD10186.doc 43 29 March 2009