SEPARATION, PROCESSING &

TRANSFORMATION OF SOLID
WASTE

NONI/FSG/UITM PAHANG
 Source-separated waste materials are recovered/
collected before they can be recycled.
 2 ways:
1. Drop-off center:
 Requires residents/businesses to separate recyclable
materials at the source
 Then, bring the materials to a specified drop-off
centers.
 Located usually at shopping centers & supermarkets
(more convenient)
 Also mobile collection centers, which can moved to
new locations periodically.
2. Buy-back center:
 Refer to a drop-off center that provide a monetary
incentive to participate.
 Residents are paid for their recyclable materials.
 Paid either directly or indirectly through reduction in
monthly collection and disposal fees.
 Also mobile collection centers, which can moved to
new locations periodically.
Drop – off container: Buy-back center:
Igloo type Using trailer / mobile
transport
 Separation is a necessary operation in the recovery of
SW
 Can be accomplished either at the source of generation
or at MRFs

1. Waste separation at source

 Usually accomplished manually.
 Number & type of components separated depend on
the waste diversion goals.
 Still need additional separation & processing
 Recycling in Germany
 What can be recycled?
2. Waste separation at MRFs:
 Function as centralized facility for separation,
cleaning, packaging & shipping of large volume of
materials recovered.
 Can be accomplished manually or mechanically.
 Current trend: integration of both manual &
mechanical separation function.
 Behind the Scene : MFR
 Designed to:
1. Modify the physical properties of the waste so
it can be removed more easily.
2. Remove specific components & contaminants
from the waste stream
3. Process & prepare the separated materials for
subsequent uses.
1. SIZE REDUCTION
 As collected materials are mechanically reduced in size
 In practice, used the term shredding, grinding, milling.
 Type of equipments: shredder, glass crusher, wood grinder
a) Hammer mill shredder
 Very effective with brittle materials
 Can be designed in: horizontal-shaft / vertical-shaft
 An impact device in which a number of hammers are
fastened to an inner shaft /disc that is rotated at high speed.
 As SW enter, they are hit with sufficient force to crush/tear &
with such velocity, they do not adhere to the hammers.
 Then, wastes are being struck against breaker plates/cutting
bars in the inner chamber.
 The cutting action continue & falls out of the bottom of the
mill.
 Hammer Mill for Waste
b) Shear shredder
 Operate in scissor-like action, which 2 counter-
rotating knives cut/shear the waste
 Low speed device (compared to hammer mill)
 Most driven by hydraulic motors that can be reversed
automatically in the event of a jam.
 The waste directed to the center of the counter-
rotating shafts.
 The shredded material drops/pull through the unit.
Shear Shredder Machine
c) Glass crusher
 Used to crush glass container & other glass products.
 To reduce storage & shipping costs
 Also to facilitate its removal by screening.
 Glass Crusher
 Glass to Counter Top
d) Tub grinder (wood grinder)
 Widely used in processing yard wastes
 Either as a mobile hammer mill shredder that can be taken
to the source/ stationary hammer mill shredder.
 Consist of large tub (feed throat) having a revolving upper
section & stationary lower section containing hammer mill
 The rotary motion of the tub conveys the materials into
the hammer mill shredder.
 The continuous stream of shredded material is carried
away from the grinder by a conveyor.
 The large –sized material used as biomass fuel/bulking
agent in composting & fine material usually composed.
 Factors to be considered in the selection of size reduction equipment

Factor Comment
Mechanical characteristics of the material must be known
Materials to be shredded
(shear strength & ductility)
Hammer mills tend to produce non-uniform product,
Size requirement for
shear shredders produce more uniformly shredded
shredded material
materials
Method of feeding Capacity of feed conveyors must be matched to the
shredder shredder
Energy requirements, routine maintenance requirement,
Operational
simplicity of operation, noise output, air & water pollution
characteristics
control requirement
Floor space & height, access & environmental
Site consideration
consideration
Material storage & Shredded materials need to be stored & conveyed to
conveyance requirement downstream operations
 SEPARATION, PROCESSING &
TRANSFORMATION OF SOLID
WASTE

NONI/FSG/UITM PAHANG
2. SIZE SEPARATION(SCREENING)
 To separate mixtures of materials of different size.
 Can be accomplished either dry/wet
 Screen has been used before & after shredding
 Types of equipment:
a) Vibrating screen
 Most used to separate dry materials (glass/metals)
 Also used to separate wood chips, removal of broken pieces
of concrete
 Can be designed to vibrate from side to side,
vertically/lengthwise.
 The vertical motion allows the material that is to be
separated to contact the screen at different locations each
time.
 b) Trommel screen
 Most versatile types of screens for SW processing
 Used to separate material into several size fractions.
 Consists of large diameter screen, formed into cylinder &
rotating on a horizontal axis.
 The material introduced at the front end of the inclined
rotating trommel.
 Trommel equipped with metal blades/teeth
 As the screen rotates, the material tumbles and contact the
screen numerous time.
 Small particles: fall through the hole in the screen, oversized
particle: pass through the screen
 Trommel Screen
c) Disc screen
 Consist of sets of parallel horizontal shafts equipped with
interlocking lobed discs.
 The undersized materials to be separated fall between the
spaces in the discs.
 Oversized materials ride over the top of the discs as in
conveyor belt.
 Different sized materials can be separated using the same
screen by adjusting the spacing between the rotating discs
 Advantages: self-cleaning & adjustability of the spacing of
discs.
 Disc Screen Separator
  Factors to be considered in the selection of screening equipment

Factor Comment
Particle size, shape, bulk weight, moisture content,
Waste characteristic
particle size distribution
Material specification for Performance characteristic of screen should match
screened components required products
Size of opening, total surface screening area, oscillation
Screen design parameters rate (vibrating screen), rotational speed (trommel),
loading rates, length, elevation angle (trommel)

Separation efficiency Recovery, efficiency, purity (%)

Energy requirement, maintenance, complexity of

Operational characteristic
operation, noise, air & wastewater emission

Site factor Floor space & vertical space availability, access

3. DENSITY SEPARATION
 To separate materials based on their density & aerodynamic
characteristics.
 Separated into: light fraction (paper, plastic, organic) &
heavy fraction ( metal, wood, dense inorganic)
 Types of equipment:
a) Air classifiers
 Most widely used in separation technology
 A complete air classification system is comprised of
conveyors, the classifier & cyclone separation.
 Air moving upward from the bottom of the chute is used to
transport the lighter materials to the top of the chute.
 The heavier materials will drop to the bottom.
b) Stoner
 To separate heavy grit from organic material in undersized
stream
 Basic stoner consist: vibrating porous deck through which air
is blown.
 Deck vibrates in a straight line in the uphill direction.
 Material is fed onto the deck at a point between the center &
the uphill third of the deck.
 Low pressure air moving up through the deck & separated the
material according to the differences in terminal velocity
 Light materials lifted & flow downhill, heavier materials
remains on the deck surface & conveyed uphill
 List of 7 Top Waste Separation Methods Used in MRF's
  Factors to be considered in the selection of separation equipment
Factor Comment
Characteristic of shredded Particle size, shape, bulk weight, moisture content,
materials particle size distribution, fiber content
Material specification for
Particle size, particle size distribution
light fraction

Transfer method for material

Conveyor characteristic & specification
to & from the separation unit

Air classifier design Air/solid ration, unit capacity, total airflow, pressure
parameters drop, fluidizing velocity

Stoner design parameters Bed slope, fluidizing air, exhaust air

Energy requirement, maintenance, complexity of

Operational characteristic
operation, noise & air emission

Site factor Floor space & vertical space availability, access

 SEPARATION, PROCESSING &
TRANSFORMATION OF SOLID
WASTE

NONI/FSG/UITM PAHANG
4. MAGNETIC & ELECTRIC FIELD SEPARATION
 Use magnetic properties & electrostatic charge of waste
materials to separate materials
 Most common technology for separating ferrous from
nonferrous metals (magnetic separation)
 To separate plastics from paper (electrostatic separation)
 Types of equipment:
a) Electrostatic separation
 Not in widespread use.
 High voltage electrostatic field used to separate
nonconductors of electricity (glass, plastic, paper) from
conductors (metals)
 Also possible to separate nonconductors from each other
b) Magnetic separation
 Permanent magnet/electromagnet can be used.
 Many types of configuration/systems:
i. Belt-type magnetic separator
 Has 3 magnets
 1st magnet: to attract the metal
 Transfer magnet: to convey the attracted materials around a curve
& to agitate it. The nonferrous metal will fall away freely.
 Final magnet: to pull the ferrous metal back to the belt & discharge
to another conveyor/storage containers
ii. Two drum magnetic separator
 1st drum: to pick up ferrous metal from the shredded waste & toss it
forward to intermediate conveyor
 Nonmagnetic materials will fall to a take away conveyor located at
below
 2nd drum: usually smaller & positioned closer to the conveyor.
Belt-type magnetic separator
Two-drum magnetic separator
Two-drum magnetic separator
 Factors to be considered in the selection of magnetic separation
equipment
Factor Comment
Characteristic of material to Particle size, shape, processed distribution, moisture
be separated content, material composition
Material specification for
Purity, recovery & efficient requirement
separated materials

Transfer method for material

Conveyor characteristic & specification
to & from the separation unit

unit capacity, power requirement, magnet strength,

Device design parameters
electrostatic field strength
Energy requirement, maintenance, complexity of
Operational characteristic
operation, noise & air emission

Site factor Floor space & vertical space availability, access

5. DENSIFICATION (COMPACTION)
 Increase the density of waste materials (more efficient to
store & transport)
 Several technologies: baling, cubing & pelleting
 Purpose:
 Reduction of storage requirement
 Reduction of volume for shipping
 Preparation of densified refuse-derived fuels (dRDF)
 Types of equipment:
a) Stationary compactor
 Waste brought to & loaded into the compactor either
manually/mechanically
 Used mechanism to compress waste in the collection vehicle
 Described according to their application as:
 Light duty (residential MSW)
 Commercial/light industrial
 Heavy industrial
 Transfer station
 In general, all compactors in application (except transfer
station) classified as low pressure units.
b) Baling equipment (baler)
 Alternative for compaction equipment
 Operating under high pressure
 Produce small compact bales of SW/recovered materials
 Most common recycled materials can be baled (cardboard,
newsprint, plastics, aluminum cans)
 Baled materials are easy to load & have high bulky density
(economically shipped)

c) Cubing & pelleting equipment

 Technology used to produce dRDF for combustion
 A complete cubing & pelleting system requires a shredder,
conveyor & moisture control system.
NONI/FSG/UITM PAHANG
1. Lack of space
 To find suitable sites for landfills, pollution, hygiene &
other issues must be considered
 Most available land left in the country is not suitable at
all.
2. Water pollution
 Most land areas in our country are water catchments
areas.
 Toxic leathers from decomposing waste will pollute our
water supplies
3. Air pollution
 Natural decomposition-methane gas & sulphur
 Foul smell, air pollution & global warming
4. Compromising health
 Exposure to disease
 Rats, flies & cockroaches-vectors & vermin
5. Product reused
 Reduce the amount of material that are to be manage as
waste
6. Material volume reduction
 Control the waste generated & disposal
7. Toxicity reduction
 Reduce the adverse environmental impact
8. Increase product lifetime
9. Decrease consumption
1. Education & research
 Education through syllabus in school, collage & university
 Research by universities with a collaboration with government &
NGO’s
 Exploring & developing funding sources
 Developing media campaign for public

2. Financial incentives & disincentive

 Linking to economic benefit
 Tax credit/exemption
 Variables waste disposal charges for garbage collection
 Product disposal charge can be assessed on the producer/consumer

3. Regulation
 Quantity control regulation
 Product design regulation
1. Cost reduction
 Reducing the waste disposal cost
 Generate revenue by sale of recyclable
2. Employment
 To ease unemployment problem
 Can create additional job for skill & unskilled workforce
3. Energy saving
4. Reduce health care cost
5. Saving cost for other public utilities
1. Improve environment
 Reducing the waste to dispose thereby reducing in
pollution
 Example: less waste to landfill after recycling, reduce in
water & land pollution

2. Natural resources
 Reduce exploration for new raw material by industries
 Example: using recycling paper means lower demand for
wood (less cutting of tree)
 Involve people with normally low social &
economic standing
 Recycling activities help to develop hierarchical
social & economic status
 Provide additional earning by selling recycling
product
 Recycling can generate higher income than
working another sector which the recycling
activities as a business
 Reliable supply of waste material
 Means to collect the material & transport
them to a place to be reprocessed
 Means to reprocess the materials into a
suitable raw materials & products
 Available markets for raw materials &
products produced by the recycling process.
1. Contamination
 Household wastes are mixture of potentially
reclaimable materials & gross contamination
 2 main categories of contamination:
 Residual contamination
not removed during pre treatment & processing
operations & which impair the recycled
material/product
 Non residual contamination
can be removed by processing but the removal reduces
the yield of the reclaimed products
2. Collection
 Major options for recovering recyclable materials:
 Bring systems- cheap to operate & recover the
recyclable materials in a clean & well segregated
state.
 Collect system- recover large amounts of clean
well segregated recyclables. Household no need
to deliver the recyclables to recycling centre
(door to door, kerb side system)
 Centralized system- access to all of potentially
recyclable material in household waste.
3. Standard
 Raw materials must conform to specifications
 Specification limit the nature & levels of
contaminants tolerable
 Based on contamination level found in primary
raw materials
 Different end users can require different
standards, provide a range of products to suit all
market requirement
1. Standard
 Refer to the segregation of the recycling &
reusable material at the point of generation
 Voluntary/mandate by government

2. Type of collection
 Drop off-deliver recycling material to provided
bin
 Buy back-provides monetary incentive to
participate
 Curb side-waste collector collect the recycling
item together with separated item
3. Storage & collection
 Resident convenience-easy way to separated
 Collection crew convenience-loading & sorting
 Cost effective-equipment & procedures
 Integrity of material-shape of material

4. Collection vehicle
 Design specifically to collect recycling material
 Capacity, flexible & weather proof
5. Processing equipment
 Bailer-compress the material
 Can crusher & compressor
 Glass crusher-break into small
 Magnetic separator-remove ferrous
material from mixture of material
 Wood grinder-shred large wood into chip
 Scales-measure the quantities of material
NONI/FSG/UITM PAHANG