Environmental Engineering

1. Waste Collection

2. Lesson Objectives
 Understand problems and concerns associated with
MSW collection.
 Compare and contrast privately and publicly
operated systems.
 Understand the types of collection systems

3. Waste Collection
History:
 Wagons and other means had been used for centuries to
haul away solid waste.
 Trucks were first used for this purpose soon after their
invention.
 The 1920s saw the first open topped trucks being used, but
due to poor odours and waste falling from the back
covered vehicles soon became more common.
 These covered trucks were first introduced in more densely
populated Europe then in North America, but were soon
used worldwide.

4. Waste Collection
 The main difficulty was that the waste collectors
needed to lift the waste to shoulder height.
 The first technique developed in the late 20s to
solve this problem was to build round
compartments with massive corkscrews that
would lift the load and bring it away from the rear.
 A more efficient model was the development of
the hopper in 1929. It used a cable system that
could pull waste into the truck.

5. Waste Collection
In 1997 Lee Rathbun, introduced
the Lightning Rear Steer System.
This system includes an elevated, rear-
facing cab for both driving the truck and
operating the loader.
This configuration allows the operator to
follow behind haul trucks and load
continuously.

6. Types of Waste Collection
Systems
Refuse Collection Systems (residential)
Commercial Waste Collection
Recyclable Material Collection

7. Refuse Collection
(Residential)
Stationary container emptied into truck
– Manually
• High injury rates (heavy containers, broken
glass/sharp objects)
• Temporary containers that fall apart
– Automatic

8. Rear Loading Compactor
Rear loaders have an opening at the
rear that a waste collector can throw
waste bags or empty the contents
of bins into. Often in many areas they
have a lifting mechanism to
automatically empty large carts without
the operator having to lift the waste by
hand

9. Rear Loading Compactor
 The modern rear loader usually compacts the
waste using a hydraulically powered plate
that scoops the waste out from the loading
hopper and compresses it against a moving
wall.
 In most compactor designs, the plate has a
pointed edge on its leading edge, which is
designed to apply point pressure to the waste
to break down bulky items in the hopper
before being drawn into the main body of the
truck.

10. Rear Loading Compactor

11. Side Loader
 These trucks are loaded from the side, either
manually, or with the assistance of an
automated lift. Lift-equipped trucks are referred
to as automated side loaders. The refuse is
then compacted towards the rear of the truck.
 An Automated Side Loader only needs one
operator where as a traditional rear load
garbage truck may require two or three people
and has the additional advantage of reducing
on the job injuries to due repetitive heavy lifting.

12. Side Loader

13. Automatic Collection
Usually only one driver required
Works best
– without on-street parking, low hanging
wires, narrow streets
– Where commitment to preventative
maintenance
– Where commitment to educating public

14. Automated Collection

15. Commercial Waste Collection
Mechanically front loaded
Hoist trucks
Trash Trailers

16. Front Loading Compactor
 Front loaders generally service commercial and industrial
businesses using large waste containers with lids known
as Dumpsters in the US. The truck is equipped with automated
forks on the front which the driver carefully aligns with sleeves on
the waste container using a joystick or a set of levers.
 The waste container is then lifted over the truck. Once it gets to the
top the container is then flipped upside down and the waste or
recyclable material is emptied into the vehicle's hopper.
 Once the waste is dumped, it is compacted by a large blade called a
"packer blade" that pushes the waste to the rear of the
vehicle. Most of the newer packing trucks have "pack-on-the-go
hydraulics" which lets the driver pack loads while driving,
allowing faster route times.

17. Front Loading Compactor

19. Collection with Recycling
 Collection of mixed MSW with sorting at MRP
(single stream)
 Collection of separated recyclables and
MSW(dual stream)
– Hand sorting of recyclables at MRP
– Hand sorting at point of collection (multi-
compartment trucks)
– Collection of separate yard waste
• Bags, bins, or carts (require automation)
• Vacuum collection
• Dual compartment collection vehicle

20. Recycling Hauler

21. Split Body Rear Loader

22. Vacuum Collection

23. Collection Options
Public Collection
Private Collection

24. Labor
Labor intensive
Labor unskilled
High turn-over rates
Few prospects for mechanical
replacement of manual labor
Injuries and poor working conditions
Limited career opportunities

25. Customer Service
Frequency of service
Container and storage issues
particularly for commercial and
industrial
Location of pickup
Special wastes

26. Management and Financing
Issues
Low priority
Resistance to change and new
technologies
Lack of quality management
Changing with new regulations

27. Technological Issues
 Collection of recyclables, yard waste, special
wastes
 Yard waste containers - bagged material
must be debagged prior to composting
 Automated collection
 Development of efficient routes
 Vehicle weight restrictions
 Vehicle turning radius and clearance

28. Reasons for declining
collection frequency include
 Proportion of putrescible waste declined
(food grinders)
 Better design of collection vehicles controls
odors and flies
 Service costs increased
 Time between collection and disposal
decreased
 Better management

29. Safety
Third most dangerous job behind
fishing and timber cutting
– Falls off trucks
– Hit by cars
– Inappropriate disposal of wastes
– Lifting injuries

30. Fixed Factors Affecting
Design and Cost
 Fixed Factors
 Climate
 Topography
 Layout - container access (alley, curbside,
rear of house)
 Available transportation systems, traffic,
roads (Venice uses boats)
 Types of wastes collected
 Population density

31. Variable Factors Affecting
Design and Cost
Storage techniques employed
Recycling
Collection frequency
Crew size
Equipment

32. Y = a + b + c(d) + e + f + g
Where:
Y = total collection time/day or week
a = garage to route time/day or week
b = actual time collecting waste/day or week
c = number of trips to disposal site/day or week
d = time to drive fully loaded truck to disposal facility,
unload and return to collection area/trip
e = time to drive to garage at the end of the trip/day or week
f + g = off route time, can be expressed as a fraction of Y/day or week
Collection Cost Calculations

33. N = SF/XW
Where:
N = number of vehicles required
S = total number of customers served per week
F = collection frequency
X = number of customers truck can serve per day
W = number of work days per week
Collection Cost Calculations -
Cont’d

34. Hauled Container System
1 2 3 4 5
Disposal Site
Number of Containers = n
Example below: n=5
The number of
drive between
containers =
n-1
Example: dbc = 4

35. Thanks