Solid Waste Collection
Collection cost has been estimated to represent about 60 to 75 percent of the total cost of solid waste management, depending on the disposal method. Because the cost of collection represents such a large percentage of the total cost, the design of collection systems must be considered carefully. The type of service provided, the frequency of service, and the equipment used for collection are considered in the following discussion.
Type of Service
The type of collection service provided will depend on the community solid waste management program. Typical examples of the types of collection service provided for the collection of (1) commingled and (2) source-separated and commingled wastes, as reported in Table 3.8. It should be noted that numerous other variations in the service provided have been developed to meet local conditions. In addition to routine collection services, presented in Table 3.8, annual or semiannual special collections for appliances, tires, batteries, paints, oils, pesticides, yard wastes, glass and plastic bottles, and "spring cleaning" have proven to be an appreciated community service while at the same time providing environmental protection.
The frequency of collection will depend on the quantity of solid waste, time of year, socioeconomic status of the area served, and municipal or contractor responsibility. In residential areas, twice-a-week solid waste collection during warm months of the year and once a week at other times should be the maximum
FIGURE 3.5 Typical containers used for collection of large amounts of waste from commercial establishments: (a ) open top with lids; (b) closed container coupled to stationary compactor.
permissible interval. In business districts, solid waste, including garbage from hotels and restaurants, should be collected daily except Sundays (see Figure 3.6). Depending on the type of collection system, the containers used for the on-site storage of solid waste should be either emptied directly into the collection vehicle or hauled away emptied and returned or replaced with a clean container. Solid waste transferred from on-site storage containers will invariably cause spilling, with resultant pollution of the ground and attraction of flies. If other than curb pickup is provided, such as backyard service, the cost of collection will be high. Nevertheless, some property owners are willing to pay for this extra service. Bulky wastes should be collected every three months. Most cities have also instituted ongoing programs for the collection of household hazardous wastes, typically every three months.
Types of Collection Systems
Solid waste collection systems may be classified from several points of view, such as the mode of operation, the equipment used, and the types of wastes collected. Collection systems can be classified, according to their mode of operation, into two categories: (1) hauled container systems and (2) stationary container systems. The individual systems included in each category lend themselves to the same method of engineering and economic analysis.8 The principal operational features of these two systems are delineated as follows.
Hauled Container Systems (HCSs) These are collection systems in which the containers used for the storage of wastes are hauled to a materials recovery facility (MRF), transfer station, or disposal site, emptied, and returned to either their original location or some other location. There are two main types of vehicles used in hauled container systems: (1) hoist truck for containers in the size range from 2 to 12 yd3 and (2) tilt-frame vehicles for containers in the size range from 10 to 50 yd3 (see Figure 3.7). Typical data on the containers and container capacities used with these vehicles are reported in Table 3.9. In addition trash-trailers are used in some locations for construction and demolition wastes.
Hauled container systems are ideally suited for the removal of wastes from sources where the rate of generation is high because relatively large containers are used (see Table 3.9). The use of large containers eliminates handling time as well as the unsightly accumulations and unsanitary conditions associated with the use of numerous smaller containers. Another advantage of hauled container systems is their flexibility: Containers of many different sizes and shapes are available for the collection of all types of wastes.
Stationary Container Systems (SCSs) In the stationary container system, the containers used for the storage of wastes remain at the point of generation, except when they are moved to the curb or other location to be emptied. Stationary container systems may be used for the collection of all types of wastes. The systems vary according to the type and quantity of wastes to be handled, as well as
FIGURE 3.7 (continued)
the number of generation points. There are two main types: (1) systems in which manually loaded collection vehicles are used (see Figure 3.8) and (2) systems in which mechanically loaded collection vehicles are used (see Figure 3.9).
The major application of manual loading collection vehicles is in the collection of residential source-separated and commingled wastes and litter. Manual loading is used in residential areas where the quantity picked up at each location is small and the loading time is short. In addition, manual methods are used for residential collection because many individual pick-up points are inaccessible to mechanized mechanically loaded collection vehicles. Special attention must be given to the design of the collection vehicle intended for use with a single collector. At present, it appears that a side-loaded compactor, such as the one shown in Figure 3.8a, equipped with standup right-hand drive, is best suited for curb and alley collection.
In most hauled container systems, a single collector-driver is used. The collector-driver is responsible for driving the vehicle, loading full containers onto the collection vehicle, emptying the contents of the containers at the disposal site (or transfer point), and redepositing (unloading) the empty containers. In some cases, for safety reasons, both a driver and helper are used. The helper usually is responsible for attaching and detaching any chains or cables used in loading and unloading containers on and off the collection vehicle; the driver is responsible for the operation of the vehicle. A driver and helper should always be used where hazardous wastes are to be handled. Labor
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