DISPOSAL OF SW AND RESIDU AL MATTER.pptx

05/21/2025 Prepared by Eng. Rweyemamu D.R. (PhD) 1
DISPOSAL OF SWs AND RESIDUAL
MATTER
SECOND YEAR: SEMESTER III

INTRODUCTION:
 The safe and reliable long-term disposal of SWs
residues is an important component of ISWM.
What are SWs residues?
 These are waste components that are not recycled,
that remain after processing at a MRFs, or that remain
after the recovery of conversion products and/or
energy.
 Historically, SW has been placed in the soil or
deposited in the oceans.
 Nevertheless, landfilling or land disposal is today the
most common used method for waste disposal by far.
MATTER

THE LANDFILL METHOD OF SW DISPOSAL
The landfill management incorporates the following:
 Planning, Design, Operation, Closure and Post-
closure control of landfills.
The purposes of this section are:
1. To introduce to you the landfilling processes
2. To review the principal reactions occurring in
landfills
3. To identify environmental concerns associated
with landfills
MATTER

Definition of terms:
 Sanitary Landfills: This is the engineered facility
for the disposal of MSW designed & operated to
minimize public health & environmental impacts.
 What does the term “Landfilling” mean?
Is the process by which residual SWs is used to fill the
excavated land It includes:
i. Monitoring of the incoming waste streams
ii. Placement and compaction of the wastes
iii. Installation of landfill environmental monitoring &
control facilities
MATTER

Definition of terms cont...
 Cell: Is used to describe the volume of material placed in a
landfill during the operating period (usually 1day). It includes
the followings:
i. The solid waste deposited & the daily cover material
surrounding it.
ii. The daily cover should be of 6 to 12inche of native soil or
alternative materials such as compost.
Why Daily cover?
1. To control the blowing of waste materials (fire).
2. To prevent rats, flies, & other disease vectors from entering or
exiting the landfill.
3. To control the entry of water into the landfill during operation.
MATTER

Definition of terms cont....
Leachate: The liquid that collects at the bottom of a
landfill.
Where does leachate come from?
It is a result of the percolation of uncontrolled runoffs and
irrigation water into the landfill.
It can also include water initially contained in the wastes
as well as infiltrating groundwater
• It contains a variety of chemical constituents derived from
solubilization & products obtained due to chemical &
biochemical reactions of the materials deposited in the
landfill.
MATTER

05/21/2025 Prepared by Eng. Rweyemamu D.
(PhD)
7
Landfill gas: The mixture of gases found within the
landfill. The bulk of landfill gas consists of methane
(CH4) and carbon dioxide (CO2), which are the
principal products of anaerobic decomposition of the
biodegradable organic fraction of the MSWs in the
landfill.
• Other components of the landfill gas includes:
atmospheric nitrogen & oxygen, ammonia & trace
organic compounds.
MATTER

Landfill liners: These are materials (both natural &
manufactured) that are used to line the bottom area and
below grade-sides of a landfill.
• Liners usually consists of layers of compacted clay and/or
geomembrane material designed to prevent migration of
landfill leachate & landfill gases.
Landfill control facility: Includes liners, landfill leachate
collection & extraction system, landfill gas collection &
extraction system and daily & final cover layers.
MATTER

Environmental monitoring: Involves the activities,
associated with collection & analysis of water and air
samples, that are used to monitor the movement of landfill
gases and leachate at the landfill site.
Landfill closure: Is the term used to describe the steps
that must be taken to close & secure a landfill site once
the filling operation has been completed.
Post-closure care: Refers to the activities as-associated
with the long-term monitoring & maintenance of the
completed landfill (Typically 30 to 50 yrs).
MATTER

WHO CAN TELL THE DIFFERENCE?

MATTER
Overview of landfill Planning, Design and
Operation:
The principal elements to be considered includes:
Landfill layout and design
Landfill operations and management
The reactions occurring in landfills
The management of landfill gases
The management of leachate
Environmental monitoring
Landfill closure and Post-closure.
See the next slide for more clarifications!

05/21/2025 Prepared by Eng. Rweyemamu D.R.
(PhD)
12
Env. Monitoring Leachate Management Landfill Operations

Development & completion of a SW landfill.

MATTER
Preparation of the site for sanitary landfill construction:
What are the major steps to be followed?
1. Preparation of the site for landfill construction
 Existing site drainage must be modified to route any run-off away from
the intended landfill area.
 Construction of access roads & weighing facilities and installation of
fences.
2. Excavation & preparation of the landfill bottom & subsurface sides.
 Modern landfills are constructed in sections
 It is desirable to obtain cover materials from the landfill site wherever
possible
 The GW monitoring equipment is installed before the landfill liners is
laid down
 The landfill bottom is shaped to provide drainage of leachate, and a
low-permeability liner is installed
 Leachate collection and extraction facilities are placed within or on top
of the liner

Tentative steps to be followed during landfill site
preparation

MATTER
Reactions occurring in landfills:
The SWs placed in a sanitary landfill undergoes biological,
Chemical & Physical changes.
Biological reactions:
These involves the organics in MSW that lead to the evolution
of gases, & eventually liquids
The biological decomposition process usually proceeds
aerobically, for a short period immediately after deposition of
wastes (O2 depletion)
During aerobic decomposition: CO2 is produced
During anaerobic decomposition: CO2, CH4, trace amount of
ammonia, and H2S

MATTER
Reactions occurring in landfills:
Physical reactions:
These involves the lateral diffusion of gases and emission of landfill
gases to the surrounding environment, movement of leachate within the
landfill & into underlying soils, & settlement caused by consolidation and
decomposition of landfilled materials.
Why bother for landfill gas movement & emissions?
As gas evolves within a landfill, internal pressure may build & cause the
landfill cover to crack and leak or blow-up.
Water entering via cracks may enhance gas production rate and cause
more cracking and/or eruption of fires.
Escaping landfill gas may carry trace carcinogenic cpds., into the env.
Because landfill gases usually have high content of CH4 there may be
combustion and/or explosion hazards.

MATTER
Concerns with the landfilling of Solid wastes:
These are things to bare in mind during SWs landfilling:
1.The uncontrolled release of landfill gases that might migrate off-site &
cause odours and other potentially dangerous conditions.
2.The impact of the uncontrolled discharge of landfill gases on the
greenhouse effect in the atmosphere.
3.The uncontrolled release of leachate that might migrate down to
underlying Groundwater or to Surface Waters.
4.The breeding and harboring of disease vectors in improperly managed
landfills.
5.The health and environmental impacts associated with the release of the
trace gases arise from the hazardous materials that were often placed in
landfills in the past.
The goal for the design and operation of a modern landfill is to eliminate
or minimize the impacts associated with these concerns.

MATTER
LANDFILL
CLASSIFICATION,
TYPES, METHODS.
1. Classification of landfills:
Normally three classification
methods are used (Adopted
from the State of California in
1984).
Designated wastes: Are non-
hazardous wastes that may
release constituents in
concentrations that exceeds
applicable water quality
objectives.
Classification Types of
wastes
I Hazardous
wastes
II Designated
wastes
III Municipal
SWs.
Focuses mainly on GW & Surface waters rather
than landfill gas migration & air quality.

MATTER
2. Types of Landfills:
The principal types of landfills can be classified as:
a) Conventional landfills for commingled MSWs.
b) Landfills for milled Solid wastes.
c) Monofills for designated or specialized wastes.

MATTER
3. Landfilling Methods:
The principal methods used for the landfilling
of MSWs are:
a) Excavated cell/Trench method.
b)Area method.
c) Canyon method.

MATTER
3. Landfilling Methods cont..
a) Excavated cell/Trench method:
This is ideally suited to areas where an adequate depth of
cover material is available at the site and where the
water table is not near the surface.
 Typically SWs are placed in cells or trenches excavated
in the soil.
 The soil excavated from the site is used for daily and
final cover.
 The excavated cells are normally typically square.

EXCAVATED CELL/TRENCH

MATTER
b)Area method:
This is used when the terrain is unsuitable for the
excavation of cells or trenches in which to place the
solid wastes.
High groundwater table conditions necessitate the use
of area-type landfills.
Cover materials must be hauled in by track or
earthmoving equipment from adjacent land or from
borrow-pit areas.
To locations where cover materials are scarce, compost
produced from yard wastes can serve the purpose.

AREA METHOD

(PhD)
26
MATTER
c) Canyon/Depression method:
Canyons, ravines, dry borrow pits and quarries have been used for landfills.
 The techniques to place and compact SWs in canyon/depression landfills
vary with the geometry of the site, the characteristics of the available cover
material, the hydrology and geology of the site, the type of leachate and gas
control facilities to be used, and the access to the site.
 A key to the successful use of the canyon/depression method is the
availability of adequate material to cover the individual lifts as they are
completed and to provide the final cover for the entire landfill when the
final height is reached.
 Cover material is excavated from the canyon walls or floor before the liner
system is installed.
 Borrow pits and abandoned quarries may not contain sufficient soil for
intermediate cover, so that cover material may have to be imported.

Available land area for Landfill:
 In selecting potential land disposal sites, it is
important to ensure that sufficient land area is
available.
Example: Estimation of required landfill area:
Estimate the required landfill area for a community with a
population of 31,000, Assume that the following conditions
apply:
1. SW generation = 6.4kg/capita.day
2. Compacted specific weight of SWs in landfill = 800kg/m3
.
3. Average depth of compacted SWs = 20m
MATTER

(PhD)
28
Available land area for Landfill: SOLUTION
1. Determine the daily SWs generation rate:
Generation rate = 31,000 people x 6.4kg/cap.day
= 198400 kg/day.
2. Computationally, the required area is given by:
Volume required/day = 198400kg/day x 1m3
/800kg
= 248m3
/day.
Area required per year = 248m3
/day x 365days/yr x 1/20m
= 4526m2
Comments: The actual site requirements will be greater than the value computed
because of space for; buffer zone, office and service building, access roads,
utility access. (20-40 percent).
MATTER

THE END OF LECTURE

DISPOSAL OF SW AND RESIDU AL MATTER.pptx

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