Leachate Generation, Transport, and Control

Leachate Generation, Transport, and Control

Mohamed Shahrir Mohamed Zahari (Universiti Malaysia Terengganu, Malaysia), Shahrul Ismail (Universiti Malaysia Terengganu, Malaysia) and Izan Jaafar (Universiti Malaysia Terengganu, Malaysia)
DOI: 10.4018/978-1-4666-9610-5.ch006
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Abstract

This chapter will discuss in detail on the primary aspect influencing leachate generation, transport and control within the landfill area. The leachate generation will look into the various factors that contribute toward increment and reduction of water balance in the landfill cell cause by the physical, chemical and biological activities. The topic will include discuss on common methods and models for estimating water input and transformation into/inside the landfill layer. Meanwhile, leachate transport part would emphasis on the leachate movement and mobility due to the effect of waste percolation, moisture field capacity and the gravity pull. Dominant flow type and the effect upon solute transport as well as other landfill components would be emphasize within the discussion. Lastly, this chapter will elaborate on the conventional and advanced techniques that being utilized for the control of the leachate for further treatment system or as beneficial advantages in the landfill management system.
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Leachate Generation

Leachate generation is an important and necessary aspect to estimate for potential leachate leakage prevention especially into the groundwater system. Potentially leachate leakage could occur if the leachate head in the bottom liner happen to exceed 30 cm which could easily be measure by placing pressure transducer in the leachate collection well. Looking from this aspect, greater leachate generation rates would significantly increase the leachate accumulation at the bottom liners due to the downward, vertical movement of the leachate flow and mostly probably increasing the chances of leakage into the groundwater aquifer.

Leachate is produced mostly from the incoming or water input from outside primarily through rainwater infiltration apart from the water which is already present as moisture in the deposited waste stream and small fraction that could be produced from the multiple reactions inside the landfill. Usually sanitary landfills are well designed to prevent or at least minimize the water infiltration through various approaches and practices depending on the landfill owner or contractors. Therefore, overall leachate generation modeling would require information on all these aspects for overall estimation; which include the type of wastes being disposed, landfilling practice, landfill cover practices, leachate collection system and leachate recirculation (if being employed) as summarized in Table 1.

Table 1.
Landfilling aspect and the significance on leachate generation
NoLandfill AspectParametersSignificance
1Wastec) Volume of waste disposed
d) Characteristic of waste
Amount of moisture being added into the landfill cell and decomposition type or rate which could either consume or generate moisture
2Landfilling Practicec) Landfill cell unit area
d) Average high
Compaction ratio, vertical stress for the landfill layers and the influence on the moisture holding capacity
3Landfill Cover Practicee) Type of daily and interim cover
f) Thickness of the covers
g) Surface vegetation and slope
h) Site precipitation data and surface runoff
Preventing water infiltration, possible erosion by surface runoff and also potential loss as water vapor or by plant uptake
4Leachate Collection Systemc) Piping layout
d) Piping design parameter
Draining the excess water out of the landfill cell
5Leachate Recirculationc) Amount of leachate recirculation rate
d) Type of recirculation system applied
The amount of water re-added into the landfill cell, the influence on waste solubilisation and possible water vapor loss from the system

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