SANITATION

TCBE 4102 Lecture

By: Eng. Dr. Anne Nakagiri

Civil and Building Engineering Department

Kyambogo University
 Solid waste management
Waste:
“Unwanted product or material generated by households or
industries that has no value for the one who discards it”
"Wastes are materials that are not prime products (that is
products produced for the market) for which the generator has
no further use in terms of his/her own purposes of production, Indiscriminate dumping
transformation or consumption, and of which he/she wants to
dispose”
“material arising from human and animal activities that are
normally solid and that are discarded as useless or unwanted”

Wastes may be generated

• during the extraction of raw materials, the processing of raw
materials into intermediate and final products, the
consumption of final products and other human activities.
 Solid waste management
Categories of Solid Waste:
• municipal solid waste(MSW)
• construction waste and demolition waste(C&D)
• institutional waste, commercial waste, and industrial waste (IC&I)
• medical waste(also known as clinical waste)
• hazardous waste, radioactive waste, and electronic waste
• biodegradable waste

Define solid waste management

“activities associated with the control of generation, storage, collection,
transfer and transport, processing, and disposal of solid wastes in a
manner that is in accord with the best principles of public health,
economics, engineering, conservation, aesthetics and other
environmental considerations”
 Solid waste management Waste Dumping Sites in Developing
Countries

Objectives of Management of Solid Waste

• To protect environmental health
• To promote the quality of the urban environment
• To support the efficiency and productivity of the economy
• To generate employment and income
Effects of Poor Solid Waste Management
• Breeding ground for diseases carriers (diseases are spread by animals,
other vectors, through food and by direct contact).
• Air pollution
• Contaminated water.
• Fire risk - piles of waste and gas generated by these present a fire
risk.
• Connection to other services.
• Environmental pollution
 Solid waste management
Financial Effects
• Loss of productive time
• Money spent on treatment
• financial loss involving the costs associated with the
environmental damage and overall waste mgt. expenditures
Solid waste management functional elements
1. Waste generation;
2. Waste handling and separation, storage, and processing at the
source;
3. Collection;
4. Separation and processing and transformation of solid wastes;
5. Transfer and transport; and
6. Disposal
 Solid waste management
Definitions & Objectives

Integrated Solid Waste

Management (ISWM): Waste
Generators
Storage
systems Collection & Storage systems
Disposal systems

the selection and application of Households

suitable techniques Heaps

technologies, and management Commercial designated disposal

sites

programs to achieve specific

Bins

Shared bring system community container indiscriminate disposal

waste management objectives
Health Care secondary collection
Facility. Bins sites
primary collection transfer station
and goals. Institutions
Bags
incineration
Shared Bins

The essential condition of

and Bags secondary collection

sustainability implies that waste Industry

management systems must be

absorbed and carried by the
avoidance / reduction

recyclables collection/picking/recovering/scavenging

society and its local recyclables treatment/processing

communities. I.e systems must
be adapted to the particular
recyclables use

urban and area-specific SYSTEM PROCESSES

circumstances and problems.

ACTORS and STAKEHOLDERS

PLANNING, MANAGEMENT, OPERATION & MAINTENANCE and MONITORING PROCESSES

 Solid waste management
The ISWM hierarchy
Key to integrated solid waste management is the development of a waste management hierarchy,
integrating widespread elements of national and regional policy – often considered as the most
fundamental basis of modern MSWM practice.
The hierarchy classifies waste management operations
according to their environmental or energy benefits

• Prevent the production of waste or reduce the amount generated.

• Reduce toxicity or negative impacts of the waste generated.
• Reuse the materials recovered from the waste stream in their current
forms.
• Recycle, compost or recover materials for use as direct or indirect
inputs for new products.
• Recover energy by incineration, anaerobic digestion or similar
processes.
• Reduce the volume of waste prior to disposal.
• Dispose of residual solid waste in an environmentally sound manner,
generally in landfills. 3R-Concept: Reduce, Reuse, Recycle
 Solid waste management
To cover municipal solid waste management

Sources (category)
 Solid waste management
Biodegradable materials:
• Degraded easily by microorganisms (either aerobic or anaerobic Most
organic solid wastes are biodegradable.
Putrsecible materials:
• Decompose rapidly, particularly in warm weather, and unless carefully
controlled,
develop objectionable odours.
Non-putrescible material:
Types • Decompose very slowly. (Plastic and polythene bags)
Refuse materials:
• Putrescible and non-putrescible materials wastes that is discarded or
rejected (garbage, rubbish, incinerator residue, street cleaning, dead animals etc).
Lechate :
• Comprises liquids seeping from solid waste as it degrades and
decomposes. It generally contains decomposed waste, water and
microorganisms.
 Solid waste management

Categories
 Solid waste management
Rate of Generation
Quantity of Solid Waste
total collected waste / population
• The quantity of waste is required to know
• Rate changes along its flow path from the
before attempting to identify appropriate generating source to final disposal depending on
types of collection, waste collection routes how much material /resources are recycled or
and vehicles, material recycling and recovered at different stages of the solid waste
recovery facilities, and waste treatment and mgt
/or disposal facilities.
Factors affecting the generation rates:
• The quantity of waste by source of
• Status of development of the country; Socio-
generation is important in establishing economic conditions; Availability of resources;
collection design and financial strategies. Geographic location
• The figures on collected waste are more • Attitude of waste generators and / or
reliable than the figures on waste manufactures; Availability and enforcement of
generation. laws to regulate waste, and promote recycling and
resources recovery.
• Culture; Season of the year; Level of technological
advancement
 Solid waste management
Physical properties
Properties of Solid Waste Specific weight / density
Mass/weight occupied by a unit volume of material
Nature, composition and properties of solid
waste essential in selecting: plays an important role of choosing the size and nature of
collection vehicle, capacity of treatment and disposal
• Method of storage facilities
• Method and frequency of collection Bulk density (kg per cubic meter) of waste =
• Equipment used for collection • total weight of the waste found in the collection
• Size of workforce container (compacted or uncompacted) / its volume
• Potential for resource recovery Moisture content
• Choice of method of disposal ratio of the amount of water present to the total weight
of waste material for a given waste stream
• Environmental impact • Moisture content (wet weight method)=100(Ww – Wd)/Ww
• Moisture content (dry weight method)=100(Ww– Wd)/Wd
• Where, Ww=wet weight of sample
• Wd =dry weight of sample.
 Solid waste management
Physical properties Physical properties
Particle size distribution Field capacity
• size of objects may influence the collection • the total amount of moisture that can be
and disposal system used, such as retained in a waste sample subject to the
diameter of the storage bins. downward pull of gravity.
• is important in designing the collection • Is of critical importance in determining the
vehicles and mechanical recovery system, formation of leachate in landfills. Water in
and in designing biological treatment excess of the field capacity will be released as
methods leachate
• Measured using manually-manipulated
screens and reported as size distribution
curves (which represent cumulative
percentages of matter passing through
increasing screen size.)
 Solid waste management
Chemical properties Chemical properties
Ultimate analysis Proximate analysis
• It is an analysis used to ascertain the • used to evaluate the combustion properties of
percentage of each element present in a solid waste and to determine the possibility of its
waste sample. use in combustion system
• It frequently involves the % of the five involves the determination of moisture content,
primary elements shown below: volatile combustible matter, fixed carbon and ash
content
 Solid waste management
Chemical properties Example
Fusing point of ash Determine the energy content/value of a
typical sample of municipal solid waste (MSW)
• the temperature at which the ash resulting of 100 kg with the average composition shown
from the burning of waste will from a solid as in the table
clinker by fusion and agglomeration
• Ranges between 11000 C and 12000 C
Energy content
• essential of an organic fraction of solid waste
for evaluating its potential for use as a fuel in
a combustion system
• Determined using bomb calorimeter and
estimated by Dulong formula:
• Energy content (kJ/kg)= 338.2C + 1430( H –
1/8 O) + 95.4S
 Solid waste management
Example
Solution:
Determine the energy content/value of a 1. Determine the energy value for each of the constituent of
typical sample of municipal solid waste (MSW) MSW using the following equation
of 100 kg with the average composition shown Energy content (kJ/kg)= 338.2C + 1430( H – 1/8 O) + 95.4S
as in the table
 Solid waste management
Example 2:
Example
Determine the energy content/value of 100 kg
• Determine the energy content/value of a of a typical MSW sample as given in
typical sample of municipal solid waste the following table
(MSW) of 100 kg with the average
composition shown as in the table
Physical constituents of a typical municipal solid waste sample

The energy content for the given MSW sample =

1790385/100 = 17904 kj/kg
 total weight of each composition
Solid waste management
Example 2:
Determine the energy content/value of 100 kg
of a typical MSW sample as given in
the following table
Physical constituents of a typical municipal solid waste sample
Convert the moisture content to Hydrogen and Oxygen mass
a. Hydrogen = 2/18* 45.6 = 5.06 kg
b. Oxygen = 16/8* 45.6 = 40.53 kg (recall H2O = (1*2) + 16

Mass of constituents = 28.7 + 3.32 + 16.4 + 1.72 + 0.6 + 4.1 =

54.4 kg Energy content (kJ/kg) = 338.2C + 1430( H – 1/8 O) + 95.4S
= 338.2  28.7 + 1430 (8.38 – 1/8  56.93) + 95.4  0.16
Therefore, moisture content = 100 – 54.4 = 45.6 kg = 11,527
 Solid waste management
Methods for determining quantity, There are a number of solid waste collection
composition and properties of solid waste systems, with/ without source reduction
• House hold survey, Source reduction,
• Load counts Reducing the amount and/ or toxicity of waste
• Material balance before it enters the MWMS or is discharged
• Weight- volume analysis into the environment
Waste handling, separation, storage and Used to describe
processing at the source Waste minimization - waste avoidance through the
Handling actions of the waste generators to avoid generating solid
• Activities associated with managing solid waste.
waste unity it is placed in containers for • Waste utilization - comprises actions that make
the waste a useful product or raw material for other
storage, before collection processes, eliminating the need for disposal.
• It may also be required to move containers • Hazard reduction - finding ways to reduce the
to and from collection points toxicity of waste.
 Solid waste management
Why (significance) source reduction Advantages of source reduction and on-site
• It reduces both quantity and toxicity of the waste processing
• Helps to promote efficient use of discarded • Generation of clean recyclable material
products/resources • Removal of hazardous material from general
• Saves costs of construction, operation and
waste streams in order to minimize health risks
maintenance of centralized waste treatment and
disposal
to the general population, particularly the waste
handlers
Further (in relation to climate change issues)
• Reduces the consumption of energy though reuse of
• Improved working condition within waste
goods and use of minimum quantities of material in recycling plants
industries – reduction in costs on collection of raw • Improved efficiency of energy recovery
material, production of products and transportation processes. It helps to operate the waste
to consumers. • treatment system cost-effectively
• Reduction in emmissions at disposal sites • Improved quality of end-products
• Pressure on vegetative cover and trees is decreased- • Minimization of overall waste management cost
due to decrease in demand for raw materials
 Solid waste management

Strategic options to minimize waste/hazards

• Decreasing consumption of products
• Resource recovery
• Reduction of toxicity
• Awareness development
 Solid waste management
Onsite processing • It minimizes the cost of the operation and reduces
includes separation of components and treatment of maintenance problems of biological treatment and
solid wastes at or near the source of generation. recycling technologies. The economic viability of most
The key concepts around on-site processing are: biological treatment options largely depends on
• Resource recovery to generate less waste Separation of waste materials at source.
• Hazard reduction • Without sorting at source, expensive pre-sorting and
• Separation of different fraction of waste final refining technologies are required in central
Significance treatment plants to process mixed wastes.
• one of the most effective and sustainable ways to • Within an industrial setting, on-site processing
achieve resource recovery. reduces waste treatment costs, minimizes the
• It reduces hazards and diverts different fractions of regulatory burden and maximizes production
material present in the waste stream to locations for economics.
appropriate treatment in the solid waste mgt.
• It reduces the quantity of general waste and
minimizes the toxicity of the general waste stream (if
hazardous materials are diverted).
 Solid waste management
Implementation of source reduction and on- The success of source reduction and on-site
site processing: processing depends primarily on:

can be effectively implemented by • Competence of waste generators

• Motivation of waste generators
• Raising public awareness (through education • Economic incentives
programs, legislation, etc) • Convenience
• to change the behavior of consumers and industries, • Environmental education
and • Legislation
• to place the responsibility for certain products on Ways of source reduction and on-site
manufactures (product-stewardship) throughout the processing depends primarily on:
products entire life cycle including its disposal.
food waste grinding, component separation, compaction,
incineration ( in fireplaces), and composting.
 Solid waste management
Collection systems based on common Source separated materials:
practices • Waste material that have been separated at source are
collected and transported to recycling and resource recovery
Mixed (commingled) materials: facilities which generally done by formal sectors in
• The most traditional system, involves industrialized countries
collection of all (non- separated) wastes • This task is often done by the informal sectors in poorer parts
from residential and commercial of the developing countries or by the waste generators who
establishments as well as from industrial are responsible for bringing their waste to communal
enterprises. collection points or containers designated for different
• External actors either collect mixed waste fractions of the waste.
from the source of generation, or the waste • A common practice in industrialized countries is for the
generators are responsible for bringing their generators to be responsible for delivering selected separated
waste to communal collection points or materials and bulky waste (furniture, garden waste etc) to
containers. drop-off centers and buy-back centers.
• If external factors involved in the collection system, then color
coded bags, bins or rollout containers are given to the waste
generators for sorting appropriate fractions of waste for
collection by external actors
 Solid waste management
Recall

Implications of source reduction/

recycling/ onsite processing
Example 1

Effect of home recovery on energy

• Energy content by 80% cardboard = 0.8 x 61460 = 49,168 kJ
content of collected solid wastes Weight of 80% cardboard = 0.8 × 4 = 3.2 kg
Using the typical percentage • Energy content by 70% paper = 0.7× 527520 = 369,264 kJ
distribution data given before, Weight of 70% paper = 0.7 × 35 = 24.5 kg
estimate the energy content of the • Energy content by 90% wood = 0.9× 54270 = 48,843 kJ
remaining solid wastes if 80% of the Weight of 90% wood = 0.9 × 3 = 2.7 kg
cardboard, 70% of the paper and 90% Now, the total energy after recovery = 1,790,385 – 49168 –
of the wood is recovered by the 369264 – 48843 = 1,323,110 kJ
homeowner. Total weight after salvage = 100 – 3.2 – 24.5 – 2.7 = 69.6 kg
Energy content per kg after recovery = 1323110 / 69.6 = 19,010
kJ/kg
 Solid waste management
The effectiveness of residential waste separation programs
depends on the type of system used for the collection of
separated wastes. A number of communities use a collection
system in which three containers are used for recycled materials
in addition to one or more containers for non-recyclable
materials.
Implications of source reduction/ • In the three container system (system1), newspaper is placed in
recycling/ onsite processing one container. Aluminum, cans, glass, and plastics are placed in
Example 2 the second container. The remaining wastes are placed in the
Comparison of residential waste third container. The separated materials, placed in special
containers, are collected at the curb.
separation programs.
• In another system(system2), four containers are used. All paper
and cardboard materials are placed in one container. All plastic,
glass, tin cans, aluminum, and any other metals are placed in a
second container. Garden wastes are placed in the third
container, and all remaining waste materials are placed in the
fourth container.
Compare these two systems, assume newspaper represents 25
percent of the total amount of paper.
 Solid waste management

Implications of source reduction/

recycling/ onsite processing
Solution:
Determine realistically how much of the
waste stream can be separated for
recycling using the two systems,
Assume 80 percent of the available
material is separated and the participation
rate is 100 percent.
An estimate of the amount of solid waste
that can be separated shown in the table
C) Based on 80 percent recovery with 100 percent participation. If only 50 percent of the homes
participate, the recycling rate drops to about 9.6 percent.
d) Based on 80 percent recovery with 100 percent participation. If only 50 percent of the homes
participate, the recycling rate drops to about 33.2 percent.
e) Container number
Newspapers 34x0.25x0.8 = 6.8
 Solid waste management

Implications of source reduction/ recycling/

onsite processing
Solution:
as shown in above computation table, the amount of
material separated for recycling with system1 is 19.2
percent versus 66.4 percent for system2.
If the participation rate were to drop to 50 percent,
the corresponding amounts are 9.6 versus
33.2percent.
Note using system1, it will be difficult to achieve the
25 percent recycling goal without a high degree of
homeowner participation.
Using system, both the 25 and 50 percent diversion
goals are achievable with a reasonable amount of
homeowner participation.
 Solid waste management

Collection containers
 Solid waste management
Factors that must be considered in the Factors that must be considered in the
onsite storage of solid wastes include: onsite storage of solid wastes include:
1. The effects of storage on the waste 2. The type of container to be used
components types and capacities of the containers used
a. Biological decomposition, depend on:
Food and other wastes (putrefaction) - a. The characteristics and types of solid
immediately undergo microbiological wastes to be collected,
decomposition. Long storage flies can start to b. The type of collection system in use,
breed and odorous compounds can develop. c. The collection frequency, and
b. The absorption of fluids and d. The space available for the placement of
Re-equilibration takes place due to difference containers.
in initial moisture contents
c. The contamination of waste components.
Major components may be contaminated (by
motor, oils, household cleaners, and paints)
reducing the value for recycling
Solid waste management Factors that must be considered in the
onsite storage of solid wastes include:
3. The container location
Container storage locations depends on the
type of the dwelling or commercial and
industrial facilities, the available space, and
access to collection services.
4. Public health and aesthetics
Public health concerns are related primarily
to the infestation of areas used for the
storage of solid wastes with vermin and
insects that often serve as potential disease
vectors. Thus
• The use of containers with tight lids,
• The periodic washing of the containers as well as of the
storage areas, and
• The periodic removal of biodegradable materials (usually
within less than 8 days), which is especially important in
areas with warm climate
 Solid waste management
Factors that must be considered in the Collection Of Solid Waste
onsite storage of solid wastes include: Includes gathering or picking up of solid wastes,
4. Public health and aesthetics hauling of these wastes to the location where
related to the production of odors and the contents of the collection vehicles are
the unsightly conditions that can develop emptied and unloading of the collection vehicle
when adequate attention is not given to From Low-Rise Detached Dwellings:
the maintenance of sanitary conditions. 1. Curb
• Most odors can be controlled through the 2. Alley
use of containers with tight lids 3. Setout-setback, and
• Maintenance of a reasonable collection 4. Setout
frequency. Low-and Medium-Rise Apartments.
• If odors persist, the contents of the
Curbside collection service
container can be sprayed with a masking
High-Rise Apartments.
deodorant as a temporary expedient.
• To maintain aesthetic conditions, the large containers
container should be scrubbed and Commercial-Industrial Facilities
washed periodically. Both manual and mechanical means
 Solid waste managementBasic collection scheme on the basis of
Types Of Collection Systems, Equipment And availability of services is categorized into four
Personnel groups.

Classification of Collection System Communal system

Block system
Kerbside/ Alley collection
1. Primary collection
Door- to -door collection
transportation of collected waste from or near the
source of generation by external stakeholders to
the final disposal sites but more often it involves
transportation to communal collection bins or
points, processing or transfer station
2. Secondary collection
It involves the collection of waste from
communal bins, storage points or transfer
station and
transportation to the final disposal site.
 Solid waste management
Types Of Collection Systems, Equipment
And Personnel

classification according to their mode of

operation into two categories.

Stationary container systems (SCS)

Hauled container systems (HCS)
 Solid waste management
Definition of terms/ activities involved in
Transfer Station
collection of solid wastes
A transfer station is a building or processing
site for the temporary deposition of waste.
• Transfer stations are often used as places where
local waste collection vehicles will deposit their
waste prior to loading into larger vehicles.
• These larger vehicles will transport the waste to the
end point of disposal in an incinerator, landfill, or
hazardous waste facility, or for recycling
Benefits of transfer station:
Costs--The main reason for waste transfer is to optimize
the productivity of vehicles and collection crews as they
remain closer to routes, while larger vehicles make the
longer trip to processing and disposal sites and ultimately
reduces overall costs.
It can also be integrated with other functional elements
of integrated waste management options (recycling ,
resources recovery & waste –to- energy facility) to
improve overall waste mgt
 Solid waste management
Benefits of transfer station:
Minimize collection vehicle routing complexities– Can serve as a controlled place for sorting and
thus more flexible planning process (use human & processing the waste- (Particularly in many low income
animal powered small motorized and more sophisticated countries where a thriving informal economy exists in recycling
Of waste, these stations can minimize health hazard and may
vehicles with hydraulic or pneumatic system can be used in
limit the amount of waste picking that is done in the streets,
different areas depending on the accessibility)
which will reduce the amount of waste that is scattered around
Provide an opportunity to increase waste communal bins and waste accumulation points).
density– (In areas where compaction vehicles are not Minimize traffic congestion—(It reduces the no. of
available , transfer station may be used to compact the vehicles for long distance haulage and may reduce fuel
waste so that greater quantities can be consumption thus reduce environmental pollution).
carried( most economical) at once to the final disposal Reduce maintenance costs of collection vehicles—
sites). (These vehicles stay on well paved roads and are not traveling
Minimize illegal waste dumping- (Particularly in on rough roads, particularly in landfill sites).
developing countries where the human-and –animal Improve waste dumping efficiency at final disposal
powered and small motorized vehicles are used for the
collection of waste are often unsuitable for traveling long
site– A reduced no. of vehicles at the disposal sites.
distances).
 Solid waste management
The main problems of transfer station:
 Increased traffic volume, noise and air pollution in the
surrounding areas .
 Unless they are properly maintained there is a
potential for environmental damage (lecha
odour, disease carriers, aesthetic and similar problem) in
surrounding areas.
In the planning and design of transfer station a
no. of factors should be considered:
• Location- governed by the proximity of the collection route,
access to the major haulage risolation from the community.
• Quantity of waste to be transferred/ handled
• Types & no. of primary and secondary vehicles served.
• Types of transfer operations( recycling, resource recovery,
garage for vehicles etc.).
• Equipment requirements( depends on activities at a
particular transfer station).
• Waste characteristics.
• Climate.
• Sanitation provision.
• Costs.
 Solid waste management
The main problems of transfer station:
 Increased traffic volume, noise and air pollution in the
surrounding areas .
 Unless they are properly maintained there is a
potential for environmental damage (lecha
odour, disease carriers, aesthetic and similar problem) in
surrounding areas.
In the planning and design of transfer station a
no. of factors should be considered:
• Location- governed by the proximity of the collection route,
access to the major haulage risolation from the community.
• Quantity of waste to be transferred/ handled
• Types & no. of primary and secondary vehicles served.
• Types of transfer operations( recycling, resource recovery,
garage for vehicles etc.).
• Equipment requirements( depends on activities at a
particular transfer station).
• Waste characteristics.
• Climate.
• Sanitation provision.
• Costs.
 Solid waste management
Collection Vehicle:

• Compaction vehicle
• Semi-compaction vehicle
• Non-compaction vehicle
• Container handling systems
1. Hoist truck
2. Tilt-frame loading
3. Trash-trailer

hoist-type equipment or hoist equipment, the hoist

arms, chains, and frames used to elevate, support,
transport, dump, and unload refuse containers.
 Solid waste management

Trash-trailer

Truck with tilt-frame loading mechanism used to haul and

unload large-capacity
containers.
 Solid waste management
Collection Vehicle:
careful selection of appropriate vehicles is
• Storage facilities- enclosure, bins, roll-out bins, bags,
crucial for a well functioning solid waste etc
management. The general considerations for • Quantity of waste- rate of generation and frequency
selecting a suitable vehicle are: of collection
• Territory- hilly, plain land, density of housing • Waste characteristics- constituents, abrasive, dense,
• Type of properties- detached dwellings , high – rise low-density
dwellings, commercial bld. etc • Traffic levels- vehicles should be harmonious with
• Transport regulation- permitted maximum load existing traffic
• Travel distance- distance to communal / transfer • Standardization- minimize overall maintenance costs
station or final disposal • Payload capacity- the amount of waste that can be
• Integration- possibility of integration with existing carried depends on the weight of vehicles( i.e,
practices vehicles with lower body weight can carry more
• Performance- convenience( loading height), material waste)
loading/ unloading efficiency , operating dimensions, • Size of cab- often it is overlooked although it does not
and turning radius, safety mechanism cost much
• Access road- width of road, type of surface, corner • Technical know-how- availability of skilled labour for
radius, maneuvering space operation and maintenance
• Cost- capital, operation, and maintenance cost
 Solid waste management

Thermal Processing of Municipal Solid Waste

Thermal processing is burning out a combustible

portion of solid waste in the presence of air or
oxygen could recover energy such as heat and
steam.
 Solid waste management
Waste-to-energy combustion (Incineration) • Incineration requires a relatively small
a process in which the chemical elements of the solid disposal area, compared to the land area
waste mix with oxygen or air in the combustion zone required for conventional landfill disposal.
to generate heat. • By using heat-recovery techniques the cost
Advantages of operation can often be reduced or offset
• The volume and weight of the waste are reduced through the use or sale of energy.
to a fraction of their original size. major constraints
• Waste reduction is immediate; it does not require • their capital and operation cost could be
long-term residence in a landfill or holding pond. high
• Waste can be incinerated on-site, without having • the level of sophistication needed to
to be carted to a distant area. operate them safely, (Skilled operators are
• Air discharges can be effectively controlled for required) and
minimal impact on the atmospheric environment. • the public lacks confidence in their safety
• The ash residue is usually nonputrescible, or sterile (concerned about stack emissions)
• Technology exists to completely destroy even the • Not all materials are incinerable (e.g.,
most hazardous of materials in a complete and construction and demolition wastes).
effective manner. • Supplemental fuel is required to initiate and at
times to maintain the incineration process.
 Solid waste management
Waste-to-energy combustion (Incineration) High sulfur or halogen content. (The presence of
This process occurs in the presence of excess air chlorides or sulfides in a waste will normally result in the
generation of acid-forming compounds. The cost of
for the proper mixing and combustion of waste. protecting equipment from acid attack must be balanced
The excess air required for incineration depends against the cost of alternative disposal methods for the
on the waste in question).
• moisture content, (greater the moisture content, the Radioactive waste. (Incinerators are often not
developed for the destruction of radioactive waste materials
more fuel is required to destroy the waste)
Some cases special design An incinerator should not be used
• heating value, (waste with no sign heating value less
for the firing of a radioactive waste).
ie 2000kj/kg as received, is not applicable/practical)
• Inorganic salts. (Wastes rich in inorganic, alkaline type of technology used for the combustion
salts are troublesome to dispose of in a conventional of waste.
incineration system. A significant fraction of the salt can
become airborne. It will collect on furnace surfaces, In addition to oxygen, carbon and hydrogen
creating a slag, or cake, which severely reduces the are also necessary for the combustion
ability of an incinerator to function properly)
process; they are either formed in their free
or combined states.
 Solid waste management
Waste-to-energy combustion (Incineration)
 Solid waste management
Waste-to-energy combustion (Incineration)
Categorized
according to the nature of the material which
they are designed to burn (i.e., refuse or
industrial waste). However, more than one waste
type can often be burned in a given unit.

1. Open burning
2. Single-chamber incinerators Single-chamber incinerator.

3. Tepee burners
4. Open-pit incinerators
5. Multiple-chamber incinerators
6. Controlled air incinerators
7. Central-station disposal
8. Rotary kiln incinerators
Modified jug incinerator
Open-pit incinerator
 Solid waste management
Waste-to-energy combustion (Incineration)
Categorized
according to the nature of the material which
they are designed to burn (i.e., refuse or
industrial waste). However, more than one waste
type can often be burned in a given unit.

1. Open burning
2. Single-chamber incinerators
3. Tepee burners
4. Open-pit incinerators
5. Multiple-chamber incinerators
6. Controlled air incinerators
7. Central-station disposal
8. Rotary kiln incinerators Cutaway of a retort multiple-chamber incinerator
 Solid waste management
Waste-to-energy combustion (Pyrolysis)
the destructive distillation of a solid,
carbonaceous, material in the presence of heat
and in the absence of oxygen. It is an exothermic
reaction (i.e., heat must be applied for the reaction to
occur).
Pyrolysis products can be utilized for various
purposes; for example,
• oil can be utilized directly in fuel applications
or after being upgraded to refined oil, and
• char can be used as carbon black, activated
carbon, and char oil, or as char water slurry for
fuel.
• The products of the pyrolysis process can
• also be used as chemical feedstock
 Solid waste management
Disposal of solid waste and residual matter
Disposal on or in the earth's mantle is, at
present, the only viable method for long-term
handling.
Landfilling is the method of disposal used most
commonly for municipal wastes;
Land farming and deep well injection have been
used for industrial wastes

Sanitary landfill
an operation in which, the wastes to be
disposed of are compacted and covered with a
layer of soil at the end of each days operation.
Is an engineered facility for the disposal of
MSW designed and operated to minimize public
health and environmental impacts.
 Solid waste management
1. Site selection
Factors that must be considered in evaluating
potential landfill sites are:
1. Available land area,
desirable to have sufficient area, including an
Important Aspects in The Implementation adequate buffer zone to operate for at least five years
Of Sanitary Landfills: at a given site. For shorter periods, the disposal
1. Site selection operation becomes considerably more expensive.
Take note of Location restrictions such as siting landfills
2. Landfilling methods and operations near airports, in floodplains, in wetlands, in areas with known
3. Occurrence of gases and leachate in faults, in seismic impact zones, and in unstable areas.
landfills 2. Impact of processing and resource recovery,
4. Movement and control of landfill gases 3. Haul distance,
and leachate minimum haul distances are desirable, but also consider collection
route location, local traffic patterns, and "characteristics of the
routes" to and from the disposal site, condition of the routes
traffic patterns, and access conditions
 Solid waste management
1. Site selection
4. Soil conditions geologic factors and
topography,
Steep topography presents a number of
problems.
• Equipment operation and truck access are more difficult
when steep slopes are encountered.
• Because of the exposed soil, erosion problems are more
severe as a result of rapid runoff from the steep areas.
• These problems can be overcome, but at a cost
The availability of sufficient soil suitable for cover material is
always a prime consideration. The types and quantities of
soil available at the site will be significant factors in the cost
of operation of a landfill.
• Soils are needed to provide the moisture barrier in
• the bottom of the fill and also in the cover. The soil must be
able to support the equipment used to transport and place
the refuse. When the site is completed, a soil
• capableof supporting a good vegetative cover is needed.
 Solid waste management
1. Site selection
5 Geological conditions,
• A tight clay is very effective in this role; a silty clay
is less effective but still satisfactory. The
Needed to establish the and environmental permeability is a function of the particle size and
suitable area for a landfill site with larger particles, the particle size distribution.
• In other cases it is desirable to have a porous soil
• It is equally important to have subsurface conditions
to control land-fill gas. The gas will follow the path
that protect any groundwater sources. The soil
of least resistance. Soils that have a large particle
deposits, both in depth and type, the imperviousness
size that is relatively uniform will be suited for this
of and distance to the rock strata, and the location of
role. Uniform gravel or uniform sand is the soil of
the groundwater table are all important considerations
choice. Such soils also have a role as drainage
in site selection.
layers to direct the flow of water within the landfill
• The objective is to maximize the distance from the
and cover
landfill to the groundwater table and to have the
Swelling and cracking.
maximum depth of impervious material between the
Certain soils are very prone to swelling when they
fill and the water table. This will reduce the possibility
become wet. When these soils dry, they crack,
that any leachate that may leak from the fill will
causing a break in the integrity of the soil layer. Clay
contaminate the groundwater
and silty clays are particularly susceptible to this
Permeability
problem. Clay, especially clay with a high organic content,
• A soil with a low permeability is needed to prevent
is plastic and very compressible. When loaded it is subject
the passage of water into the fill and the loss of to heaving. When wet, this type of soil is unsuited for
leachate from the landfill supporting vehicles, especially collection and transfer
vehicles.
 Solid waste management •
1. Site selection
5 Geological conditions,
Support of vegetation.
When the landfill is completed, a final cover is
placed to isolate the refuse from the environment.
It is essential to have a good cover of vegetation to
protect the soil from erosion and to serve as a
means of dissipating the water that may infiltrate
into the top layers of the cover. These soils must be
able to absorb and retain significant quantities of
water as well as plant nutrients needed for the
growth of the vegetative cover. Silt, sandy silt, and
to a lesser degree, clay-sandy silt are desirable soils
for this purpose.
It is important to remember that the cover may be
constructed of several layers of soil, each having a
specific purpose.
 Solid waste management •
1. Site selection
Hydrogeologic Properties of the Site

Condition 1 that may be encountered.

The deep aquifer is a considerable distance below the
surface. It is recharged at a distant point. The travel time
is long, so the water level will remain relatively constant.
It is also protected by an impervious stratum above.
Contamination of this aquifer is extremely improbable.
The shallow aquifer is more vulnerable; the distance to
the landfill is greatly reduced and there is no protective
layer. This aquifer has a high risk of contamination if the
landfill is should be designed to minimize the
production of and contain all leachate that may be
produced.
This figure also illustrates the importance of site
selection relative to the groundwater table.
A shallow aquifer is replenished by local precipitation.
Conse
 Solid waste management •
1. Site selection
Hydrogeologic Properties of the Site

Condition 1 that may be encountered.

This figure also illustrates the importance of site selection
relative to the groundwater table.
A shallow aquifer is replenished by local precipitation.
consequently, its level may vary considerably, being near the
surface during wet weather.
• A landfill located on the high ground will not be likely to come
in contact with the groundwater.
• However, if the site is closer to the stream, it is possible for the
groundwater to infiltrate the landfill during wet periods. It is
very difficult to prevent water from penetrating the bottom of
the landfill unless the fill contains a substantial depth of
leachate. Lifting pressure backed by many feet of water head
can be encountered. Rupture of the lining is a strong possibility
and the landfill will become saturated with groundwater.
• When the water level drops, the contaminated water will also
leak from the fill, causing pollution of the shallow aquifer
 Solid waste management •
1. Site selection
Hydrogeologic Properties of the Site

Condition 2 Perched groundwater tables

This figure also illustrates the importance of site selection
relative to the groundwater table.
An impervious layer of soil such as a clay lens may be 6 to 10m
below the surface and cover a reasonable area. The precipitation
falling in this area will percolate into the ground and form a
perched water table. The level of this water table will vary
substantially, coming very close to the surface during periods of
heavy precipitation.
Again, the groundwater may penetrate the landfill, causing
saturation of the refuse. When the water level drops, the
contaminated water will drain from the fill, causing serious
groundwater pollution. These sites are the most difficult
to evaluate unless there is a historical record of the groundwater
table levels at the specific site.
Important to evaluate any site during wet as well as dry weather
conditions
 Solid waste management
1. Site selection
Local environmental conditions, and:
if located close to residential and industrial developments.
They must be operated carefully if they are to be
environmentally acceptable with respect to noise, odor,
dust, vector control, hazards to health and property values.
To minimize the impact of landfilling operations, landfills
should be located in remote areas where adequate butter
zones surrounding the landfill can be maintained.

9.Potential ultimate uses for the completed site:

One of the advantages of a landfill is that, once it is
completed, a sizable area of land
becomes available for other purposes. Because the
ultimate use affects the design and operation
of the landfill, this issue must be resolved before the layout
and design of the landfill are started. For example, if the
completed landfill is to be used as a park or golf course, a
staged planting program should be initiated and continued
as portions of land filing
 Solid waste management
Landfill design
A landfill’s basic design parameter is volume.
 too small will not have an adequate service life
and will not justify the expense of building it.
 Too large may eliminate many potential sites and
will result in high up-front capital costs
 Thirty years seems to be an appropriate time
frame, because after thirty years, it becomes
difficult to anticipate solid waste generation and
new disposal technology
• Thus vol depends on the area covered, the
depth at which the refuse is placed, and the
ratio of soil cover to refuse.
• The air space in this fill site represents the
volume available for placing the refuse and
cover material. Since the refuse generation rate
is measured in kgs, an additional parameter that
influences the capacity of the landfill is the in-
place density of the refuse and soil.
 Solid waste management
Volume, mass, and density calculations for Example
mixed materials For illustrative purposes only, assume that
considering a container that holds a mixture of materials, refuse has the following components and
each of which has its own bulk density. bulk densities.

Percentage Uncompacted bulk

Component (by weight) density (lb/ft3)
Miscellaneous paper 50 3.81
Garden waste 25 4.45
Glass 25 18.45

Assume that the compaction in the landfill is(44.4 lb/ft 3).

Estimate the percent volume reduction achieved during
compaction of the waste. Estimate the overall uncompacted
bulk density if the miscellaneous paper is removed.
 Solid waste management
General features of a landfill
cell - the volume of material placed in a landfill during
one operating period, usually 1 day. (includes the solid
waste deposited and the daily cover material surrounding it)
A lift is a complete layer of cells over the active area of
the landfill
A bench (or terrace) is typically used where the height of
the landfill will exceed 15 to 20m.
Benches are used to maintain the slope stability of the
landfill, for the placement of surface water drainage
channels, and for the location of landfill gas recovery
piping
The final lift includes the landfill cover layer
Landfill liners are materials (both natural and man-
made) that are used to line the bottom area and below-
grade sides of a landfill
Leachate liquid that forms at the bottom of a landfill as
a result of the percolation of precipitation, uncontrolled
runoff, and irrigation water into thelandfill
Solid waste management
Solid waste management

2. Landfilling methods and operations

Methods used to fill dry areas are substantially

different from those used to fill wet areas.

The principal methods used for dry landfilling

areas may be classified as:

1. Area method
2. Trench method
3. Depression method
 Solid waste management
2. Landfilling methods and operations
1. Area method
filling operation is usually started by building an
earthen levee against which wastes are placed
in thin layers and compacted. Each layer is
compacted as the filling progress until the
thickness of the compacted wastes reaches a
height varying from 6 to 10 feet (1.8 to 3) m at
that time or at the end of each day operation a
6 to 12 in (15 to 30) cm layer of cover material
is placed over the completed fill. The cover
material must be hauled in by truck from
adjacent land. Successive lifts are placed on top
of one another until the final grade in the
ultimate plan is reached. A final layer of cover
material is used when the fill reaches the final
design height
 Solid waste management
2. Landfilling methods and operations
2. Trench method
Is ideally suited to areas where an adequate
depth of cover material is available and where
water table is well below the surface.
A portion of the trench is dug with a bulldozer
and the dirt is stock piled to form an
embankment behind the first trench. Wastes
are then placed at the
trench spread into thin layers and compacted.
The operation continues until the desired level
is reached. Cover material is obtained by
excavating an adjacent trench.
 Solid waste management
2. Landfilling methods and operations
3. Depression method
Where artificial depression occurs, it is often
possible to use them effectively for landfilling
operations. The techniques to place and
compact solid wastes in depression landfills
vary with the characteristics of the site. The
availability of adequate material to cover the
individual lifts and to provide a final cover over
the entire landfill is very important. Borrow pits
and abandoned quarries may not contain
sufficient soil for intermediate cover, so that it
may have to be imported
 Solid waste management
Design
Among the important topics that must be considered
in the design of a landfill (though not necessarily in
the order given) are the following:

1. Layout of landfill site

2. Types of wastes that must be handled
3. The need for a convenience transfer station
4. Estimation of landfill capacity
5. Evaluation of the local geology and
hydrogeology of the site
6. Selection of leachate management facilities
7. Selection of landfill cover
8. Selection of landfill gas control facilities
9. Surface water management
10. Aesthetic design considerations
11. Development of landfill operation plan
12. Determination of equipment requirements
13. Environmental monitoring
14. Public participation
15. Closure and post closure care
 Solid waste management
Landfill Cover Design
is a trade-off-in this case, between the effectiveness
of the moisture barrier and the amount of leachate
that will have to be collected and treated
Each layer has a specific function, and soils with
properties that will achieve this function are chosen
 Solid waste management
Landfill Cover Design
Landfill Cover Design
Surface layer.
function - providing a suitable medium for plant growth. Plant
growth is essential to protect the surface of the cover from
erosion (wind and water action). There will be a slope to the
final grade to assist with runoff of precipitation. It should be a
soil with a texture that allows for percolation of water
into the soil and that has a good water retention capacity.
Soils that fill this objective are silt, silt-loam, loam, and sandy-
loam soils

Biotic barrier.
function - the biotic barrier is to prevent penetration of
the moisture barrier by either burrowing animals or roots
from deep-rooted plants (trees).
coarse gravel (in case area is constantly Mowed say golf course
then this layer is not necessary)
 Solid waste management
Landfill Cover Design
Landfill Cover Design
Drainage layer.
Very important when the landfill is in an area of high
precipitation and where evapotranspiration is not an effective
mechanism for dissipating the excess water.
Its purpose is to remove the water that infiltrates the top
layer of the cover. This layer is sloped to a drain line
coarse relatively uniform sand or fine gravel
The success of this drainage layer depends on maintaining its
porosity.
Thus advisable to install a “filter” layer above the drainage
layer made of soil of particle size between those of the
drainage and surface layers or geotextiles
 Solid waste management
Landfill Cover Design Landfill Cover Design
Hydraulic barrier.
is instrumental in preventing the infiltration from reaching
the refuse. The desired type of soil is a tight clay. Sandy-
clay and silty-clay soils are suitable if a clay is not available.
The depth of the hydraulic barrier can be adjusted to reflect
the permeability of the soil
impermeable barriers can be created by amending a fine grain
soil with bentonite clay, fly ash, or some other soil additive plus G
geomembranes

shortcomings in that they can easily be damaged

Foundation layer.
significance when a geomembrane is used.
an effective moisture barrier if membrane is damaged. It
provides a “stable” foundation for the membrane, is designed
separate the membrane from the refuse and protect it from
damage by the refuse.
Constructed from any on-site soils that do not contain sharp
stones or other objects
 Solid waste management
Landfill Cover Design

Landfill Cover Design

Gas control.
Gas will be produced in the landfill as a result of the biodeg-
radation of the organic solids. Soils that prevent infiltration of
water will also prevent the gas from escaping. This gas must
be released, or it will generate sufficient internal pressure to
rupture the restraining membrane or soil moisture barrier.
This rupture will provide an avenue for infiltration of water.

layer of a porous material such as crushed stone placed on top

of the refuse. The gas can follow this layer until it reaches a
collection well
Landfill Liner Design Solid waste management
The design of the liner requires many of the same
considerations as the design of the cover.
The objective is to prevent the movement of the infiltration
(leachate) into the groundwater and to facilitate removal of
leachate
Landfill Liner Design Solid waste management
 Solid waste management
Leachate Quantity
total quantity produced can be estimated either by
using empirical data or a water balance technique
3. Occurrence of gases and leachate in
landfills Mass balance balance among precipitation,
Reaction occurrence of gases and leachate in landfills evapotranspiration, surface runoff, and soil moisture
storage
The following biological, physical and chemical events occur
when solid wastes are placed in a sanitary landfill:
• Biological decay of organic materials either aerobically or
anaerobically, with evaluation of
• gases and liquids.
• Chemical oxidation of waste materials
• Escape of gases from the fill
• Movement of liquids caused by differential heads
• Dissolving and leaching of organic and inorganic by water
and leachate moving through the fill
• Uneven settlement caused by consolidation of material into
voids.
 Solid waste management
3. Occurrence of gases and leachate in
landfills
Leachate Quantity
Mass balance balance among precipitation, evapotranspiration, surface
runoff, and soil moisture storage

Recall
Field capacity - the maximum moisture the soil (or any other material such
as refuse) can retain without a continuous downward percolation due to
gravity.
If the field capacity of this mixture is exceeded, the liquid (leachate) will
drop to the next lowest soil/refuse layer. Thus
• finished landfill, if the field capacity of the soil covering waste is
exceeded, the water percolates through the soil and into the buried
solid waste. water balance method is a means of calculating if
• in turn, the field capacity of the waste is exceeded, leachate flows into and by how much field capacities are exceeded
the leachate collection system. and, thus, is a way of calculating the production
of leachate by landfills
A soil/refuse mixture that does not attain field capacity discharges
essentially no water to the deeper layers
 Solid waste management
3. Occurrence of gases and leachate in
landfills
Leachate Quantity

The field capacity of compacted waste has been estimated as 20 to 35%

by volume (about 30%), which translates to 300 mm of water/m of MSW.

correction for moisture already contained in the refuse, which is about

15% take field capacity of 150 mm/m of refuse
 Solid waste management
3. Occurrence of gases and leachate in
landfills Leachate Treatment
Leachate Quantity
Same as that for
wastewater
 Solid waste management
3. Occurrence of gases and leachate in
landfills

Gas Quantity
Landfill operators, energy recovery project owners, and
energy users need to be able to project the volume of
gas produced and recovered over time from a landfill.

Proper landfill management can enhance both yield and

quality of gas

Mathematical and computer models used to predict gas

yields
Example LandGEM based on the following equation
 Solid waste management
3. Occurrence of gases and leachate in Gas Quantity
Example.
landfills
 Solid waste management
Gas collection

Gas generated within a landfill will move by pressure gradient,

following paths of least resistance

Passive collection systems collect landfill gas using vent

collectors and release the gas to the atmosphere without
treatment or conveyance to a common point. Passive vents are
often provided using natural convective forces within
The landfill to direct gas to the atmosphere.

Typical spacing for a passive vent is one per (7500 m3)

Active collection systems link collection wells with piping and

extract the gas under vacuum created by a central blower.
Active extraction wells may be vertical or horizontal wells,
although vertical wells are more frequently employed.
 Solid waste management
Examples
Find the amount of land required in a sanitary landfill to dispose of urban waste of a
city of 40000 in population, knowing that;
• amount of waste generation=2.5 kg/capita/d,
• density of landfill waste=500 kg/m3 and
• waste is filled into a depth of about 3m.
 Solid waste management
Examples
Find the amount of land required in a sanitary landfill to dispose of urban waste knowing that:
• City population=176119
• Waste generation rate=0.875 kg/capita/d,
• Density of landfill waste=560 kg/m3
• Waste is filled into a depth of about 8.5m
The landfill site is to be used for 13 years and 25% should be added as area necessary for
construction facilities.