CE 527 Solid Waste Management
Lecture 3 - Collection and Transfer Operations
Collection Services for Municipal Waste
• _______ - homeowner responsible for placing the containers at the curb and returning the empty container for
storage
• _______ - depending on location, homeowner may be responsible for setting out containers or placed in the alley
for collection
• _______ - containers are set out from homeowners' properties and set back after being emptied by collection
crew
• ________ - homeowner responsible for returning the containers to their storage location
Example of Types of Containers (from Table 7-4, textbook)
Type
Range
Typical
Small
Plastic pr galvanized metal
20 - 40 gal
30 gal
Disposable Plastic bags
20 - 55 gal
30 gal
Medium
Container
1 - 10 yd3
4 yd3
Large
Open top
12 - 50 yd3
Equipped with self-contained
20 - 40 yd3
compactor
Types of Collection Systems:
Hauled Container Systems
• Hoist Truck System
• Tilt-frame Container System
• Trash-Trailer Systems
Stationary Container System
• system with mechanically-loaded collection vehicle
• system with manually loaded collection vehicle
Collection Routes
A.
Basic Goals
1.
Efficient, economical and reliable collection of refuse
2.
Balanced routes and work activities of crews
B
Analysis of Collection Routes
1.
Exact Methods
Analyze all possibilities
(a) Impractical
(b) Time consuming
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Typical Dimensions
20"D x 26"H
30"W x 40"H
72"W x 42"L x 65"H (4 yd3)
8' W x 6'H x 20'L (35 yd3)
8' W x 8'H x 22'L (30 yd3)
(c) Site conditions may be different
Mathematical Models
(i) Complex
(ii) Expensive
(iii) Not adaptable to many problems
(iv) More as a screening tool
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Heuristic process - empirical investigation
(i) Relies on common sense "rules of thumb"
(ii) Requires minimum time, materials and expense
(iii) Adaptable to a wide range of problem and flexible
C.
Data Needed to Develop Collection Routes
1. Daily Collection Activity report
(i)
Average time for pickup, haul, on site and off-route
(ii)
Average pickup, hauling and off-route mileage
(iii)
Number of trips to disposal site
(iv)
Number of containers per pickup site
(v)
Average weight of SW per container
(vi)
Frequency of service needed (no. of days per week)
(vii)
Collection vehicle - capacity, maximum load, crew size
2. Detailed Community Maps
(i)
Show number of services by waste type on each street segment
(ii)
Show one-way streets dead ends, divided streets, obstructions and other
necessary details
3. Existing Route Information, if available
(i)
Indicate existing routes on the map
(ii)
Indicate current collection vehicle type and crew size
D.
Factors to consider in designing a routing system
1.
Geographical Areas - divide up into 5 basic areas (once per week collection over 5 days)
- divide into areas that will be serviced by a single crew or truck over a 5 day period
- divide into one day work areas
Division can be based on: natural boundaries (rivers, railroads, expressways)
time and distance to disposal
differences in population density
types of SW
2.
Some Considerations in Laying out Collection Routes
- continuous route with series of clockwise loops
- minimize left turns and "U" turns
- minimize "dead" distances
- avoid heavily traveled streets during rush hours - collect as early in the day as possible
- last container to be collected on the route is located nearest to the disposal site
- sources with extremely large quantities of wastes generated should be serviced during the first
part of the day
- hilly area, start at the top of the grade and proceed downhill as the vehicle becomes loaded
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Collection Analysis
Pick up -
hauled container system - conventional mode: time spent driving to the next container after an
empty container has deposited, the time spent picking up the loaded container, and the time
required to redeposit the container after its contents have been emptied
exchange container mode: time required to pick up a loaded container and redeposit the container
at the next location after its contents have been emptied
stationary container system - time spent loading the collection vehicle, beginning with stopping
the vehicle before loading the contents of the first container and ending when the contents of the
last container to be emptied have been loaded
Haul -
hauled container system - time required to reach the location where the contents of the container
are emptied (eg., disposal site) starting when a container whose contents are to be emptied has
been loaded on the truck and continuing through the time after leaving the unloading location until
the truck arrives at the location where the empty container is to be redeposited - does not include
time spent unloading at unloading location
stationary container system - refers to time required to reach the location where the contents of the
collection vehicle will be emptied, starting when the last container on the route has been emptied
or the collection vehicle is filled and continuing through the time after leaving the unloading
location until the truck arrives at the location of the first container to be emptied on the next
collection route
At-site -
time spent at the location where the contents of the container are unloaded
Off-route -
time spent on activities that are nonproductive
• necessary off-route time - time checking in and out , congestion, equipment repairs, maintenance
• unnecessary off-route - excess lunch period, talking to friends
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Hauled Container System
Stationary Container system
Thcs
Thcs = Phcs + s + h
= Phcs + s + h
h = a + bx
h = a + bx
Phcs = pc + uc + dbc
Pscs = Ct(uc) + (np - 1)(dbc)
Nd = [H (1-W) - (t1 + t2)] / Thcs
Ct = vr / cf
Nd = Vd/(cf)
Nd = Vd /vr
H = [(t1 + t2) + Nd(Tscs)]/(1-W)
where
Thcs
Phcs
s
h
a
b
x
pc
uc
dbc
Nd
H
W
t1
t2
Vd
c
f
Pscs
Ct
uc
np
v
r
c
f
Nd
Vd
t1
t2
= time per trip for hauled container system (h/trip)
= pickup time per trip for hauled container system (h/trip)
= at-site time per trip (h/trip)
= haul time per trip (h/trip)
= empirical hual time constant (h/trip)
= empirical haul time constant (h/mile)
= average round trip haul distance (mile/trip)
= time required to pickup loaded container (h/trip)
= time required to unload empty container (h/trip)
= time required to drive between container locations (h/trip)
= number of trips per day (trips/d)
= length of work day (h/d)
= off-route factor (fraction)
= time to drive from dispatch station (garage) to first container location to be serviced for the day (h)
= time to drive from the last container location to be serviced for the day to the
dispatch station (garage) (h)
= average daily quantity of waste collected (yd3/d)
= average container size (yd3/trip)
= weighted average container utilization factor
= pickup time per trip for stationary container system (h/trip)
= number of containers emptied per trip (containers/trip)
= average unloading time per stationary container for stationary container system (h/container)
= number of container pickup locations per trip (locations/trip)
= volume of collection vehicle per trip (yd3/trip)
= compaction ratio
= container volume (yd3/container)
= weighted container utilization factor
= number of collection required per day (trips/d)
= average daily quantity of waste collected (yd3/d)
= time to drive from dispatch station (garage) to location of the first container to be picked up on the first
route of the day (h)
= time to drive from the approximate location of the last container pickup on the last route of the day to the
dispatch station (garage) (h)
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Public vs Private Collection
Advantages
Disadvantages
Public Collection
 Non profit, so no additional revenue have
to be raised for profits
government operation results in purchasing advantage
 capital expenditure take longer to process
 system flexibility is more easily designed
 susceptible to political influences
 short term politics may favor cheapness instead of long term
economics
 personnel efficiency may be lower than that of private firms
Private or Contract Collection
 may be less susceptible to political interferences
 competition can increase system efficiency and improve
service
 more flexibility in establishing management structure
 can involve less strain on municipal budget
(eg., capital expenditures internal to private firm)
 profit structure and taxation costs may be passed on to customers
 community dependence on one contractor may occur minimizing
advantages accruing from competition
 third party administration (required municipal oversight)
 accountability (financial difficulties and contract problems may
hinder service.
Transfer Stations
• centralized facilities where waste is unloaded from several small collection vehicles and loaded into a larger
vehicle for hauling
• increase the efficiency of the system, as collection vehicles and crews remain closer to routes
• may be integrated with other waste management options such as recycling programs and waste-to-energy facility
operations
• significant capital and operating costs may be needed
Types of Transfer Stations
(i) direct-load
(ii) storage-load
(iii) combined direct-load and discharge load
By Size
(i) small < 100 ton/day
(ii) medium 100 to 500 ton/day
(iii) large > 500 ton/day
Transport Means
(i) Motor Vehicle Transport
(ii) Railroad Transport
(iii) Water Transport
(iv) Pneumatic transport, hydraulic transport
Transfer Station Design Consideration
(i)
Type of Transfer Station
(ii)
Transfer Station Capacity Requirements
(iii)
Equipment and Accessory Requirements
(iv)
Environmental Requirements
(v)
Health and Safety
(vi)
Siting Issues
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