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Types of Transfer Stations

Transfer stations are used to accomplish transfer of solid wastes from collection and other small vehicles to larger transport equipment. Depending on the method used to load the transport vehicles, transfer stations, as reported in Table 3.11 may be classified into two general types: (1) direct load and (2) storage load (see Figure 3.12). Combined direct-load and discharge-load transfer stations have also been developed transfer stations may also be classified with respect to throughput capacity (the amount of material that can be transferred and hauled) as follows: small, less than 100 tons/day; medium, between 100 and 500 tons/day; and large, more than 500 tons/day.

Direct-Load Transfer Stations At direct-load transfer stations, the wastes in the collection vehicles are emptied directly into the vehicle to be used to transport them to a place of final disposition or into facilities used to compact the wastes into transport vehicles (see Figure 3.13) or into waste bales that are transported to the disposal site. In some cases, the wastes may be emptied onto an unloading platform and then pushed into the transfer vehicles, after recyclable materials have been removed. The volume of waste that can be stored temporarily on the unloading platform is often defined as the surge capacity or the emergency storage

Disposal cost at landfill

Disposal cost at landfill

0 30 60 90 120 150 180 210 240 270 30C Round-trip driving time

FIGURE 3.11 Cost comparison-incineration versus transfer and haul to landfill.

capacity of the station. Small direct-load transfer stations used to serve industrial parks, rural areas, and entrances to landfills are illustrated in Figure 3.14.

Storage-Load Transfer Station In the storage-load transfer station, wastes are emptied directly into a storage pit from which they are loaded into transport vehicles by various types of auxiliary equipment (see Figure 3.1 b). The difference between a direct-load and a storage-load transfer station is that the latter is designed with a capacity to store waste (typically one to three days).

Vehicles for Uncompacted Wastes

Motor vehicles, railroads, and ocean-going vessels are the principal means now used to transport solid wastes. Pneumatic and hydraulic systems have also been used. However, in recent years, because of their simplicity and dependability, open-top semitrailers have found wide acceptance for the hauling of uncompacted wastes from direct-load transfer stations (see Figure 3.15a). Another combination that has proven to be very effective for uncompacted wastes is the truck-trailer combination (see Figure 3.15b). Transport trailers used for hauling solid waste over great distances are all of monoque construction, where the bed of the trailer also serves as the frame of the trailer. Using monoque construction allows greater waste volumes and weights to be hauled.

TABLE 3.11 Types of Transfer Stations Used for Municipal Solid Waste

Type

Direct-Load Transfer Stations

Large- and medium-capacity direct-load transfer station without compaction

Large- and medium-capacity direct-load transfer stations with compactors

Small-capacity direct-load transfer stations

Storage-Load Transfer Station

Large-capacity storage-load transfer station without compaction

Medium-capacity storage-load transfer station with processing and compaction facilities

Other Types of Transfer Stations

Combined discharge-load and direct-load transfer station

Transfer and transport operations at MRFs

Description

Wastes to be transported to landfill are loaded directly into large open-top transfer trailers for transport to landfill.

Wastes to be transported to landfill are loaded directly into large compactors and compacted into specially designed transport trailers or into bales, which are then transported to landfill.

Small-capacity transfer stations are used in remote and rural areas. Small-capacity transfer station are also used at landfills as a convenience for residents who wish to haul wastes directly to landfill.

Wastes to be transported to a landfill are discharged into a storage pit where they are pulverized before being loaded into open trailers. Waste is pulverized to reduce the size of the individual waste constituents to achieve more effective utilization of the transfer trailers.

Wastes to be transported to a landfill are discharged into a pit where they are further pulverized before being baled for transport to a landfill.

Waste to be transported to a landfill can either be discharged on a platform or discharged directly into a transfer trailer. Wastes discharged onto a platform are typically sorted to recover recyclable materials.

Depending on the type of collection service provided, materials recovery and transfer operations are often combined in one facility. Depending on the operation of the MRF, wastes to be landfilled can be discharged directly into open trailers or into a storage pit to be loaded later into open-top trailers or baled for transport to a landfill.

Source: Adapted from G. Tchobanoglous, H. Theisen, and S. Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues, McGraw-Hill, New York, 1993.

Waste discharged directly into an open-top trailer, into compaction facilities, or onto a moving conveyor for transport to processing facilities or compaction facilities

Waste from storage pit pushed into open-top transport trailers or into compaction facilities or into a moving conveyor for transport to processing facilities or compaction facilities

FIGURE 3.12 Definition sketch for two most common types of transfer stations: (a) direct discharge; (b) storage-discharge. (Source: LaGrega, M. D., P. L. Buckingham, and J. C. Evans, Hazardous Waste Management, 2nd ed., McGraw-Hill, New York, 2001.)

Transfer Station Siting Issues

A transfer station, resource recovery facility, or processing facility should be located and designed with the same care as described for an incinerator. Drainage of paved areas and adequate water hydrants for maintenance of cleanliness and fire control are equally important. Other concerns are landscaping, weigh scales, and traffic, odor, dust, litter, and noise control. Rail haul and barging to sea also involve the use of transfer stations. They may include one or a combination of grinding, baling, or compaction to increase densities, thereby improving transportation efficiency.

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