Encyclopedia of Environmental Science and Engineering, Volume I and II

Collection

Collection cost has been estimated to represent about 80% of

the total cost of collection and disposal by sanitary landfi ll

and 60% when incineration is used. In 1968 collection cost

alone was found to average 10 to 13 dollars per ton.

The frequency of collection will depend upon the quan-

tity of solid waste, time of the year, socio-economic status

of area served, and municipal or contractor responsibility. In

business districts refuse, including garbage from hotel and

restaurants, should be collected daily except Sundays. In res-

idential areas, twice a week refuse collection during warm

months of the year and once a week at other times should

be the maximum permissible interval. Slum and ghetto areas

usually require at least twice a week collection. The recep-

tacle should be either emptied directly into the garbage truck

or carted away and replaced with a clean container. Refuse

transferred from can to can will invariably cause spilling,

with resultant pollution of the ground and attraction of rats

and fl ies. If other than curb pick-up is provided, the cost of

collection will be high. Some property owners are willing to

pay for this extra service.

Transfer Station

The urban areas around cities have been spreading leaving

fewer nearby acceptable solid waste disposal sites. This has

generally made necessary the construction of incinerators in

cities or on the outskirts, or the transportation of wastes longer

distances to new sites. However, as the distance from the cen-

ters of solid waste generation increases, the cost of direct haul

to a site increases. A distance is reached (in terms of time)

when it becomes less expensive to construct an incinerator,

or a transfer station near the center of solid waste generation

where wastes from collection vehicles can be transferred to

large tractor-trailers for haul to more distant disposal sites.

Rail haul and barging to sea also involve the use of

transfer stations. They may include one or a combination of

grinding, compaction to various densities, and baling.

Treatment and Disposal of Solid Wastes

Solid waste treatment and disposal methods include the open

dump, hog feeding, incineration, grinding, and discharge to

a sewer, milling, compaction, sanitary landfi ll, dumping,

and burial at sea, reduction, composting, pyrolization, wet

oxidation, and anaerobic digestion. The common acceptable

methods are incineration, sanitary landfi ll and in some part

of the world composting.

Open Dump The open dump is all too common and needs

no explanation. It is never satisfactory as usually main-

tained. Refuse is generally spread over a large area provid-

ing a source of food and harborage for rats, fl ies, and other

vermin. It is unsightly, an odor and smoke nuisance, a fi re

hazard, and often a cause of water pollution. It should be

eliminated or its operation changed to a sanitary landfi ll.

Hog Feeding Where garbage is fed to hogs, careful susper-

vision is necessary. The spread of trichinosis in man, hog

cholera, the virus of foot-and-mouth disease, and vesicular

exanthema in swine is encouraged when uncooked garbage

is fed to hogs. In some instances, tuberculosis, swine ery-

sipelas, and stomatitis may also be spread by raw garbage.

The boiling for thirty minutes of all garbage fed to hogs will

prevent transmission of trichinosis and economic loss of the

swine industry due to hog illness and death.

Grinding The grinding of garbage is fast becoming a common

method of garbage disposal. It is highly recommended from a

convenience and public health standpoint, but the disposal of

other refuse remains to be handled. The putrescible matter is

promptly removed thereby eliminating this as a source of odors

and food for rats, fl ies, and other vermin. In one system, the

home grinder is connected to the kitchen sink drain. Garbage

is shredded into small particles while being mixed with water

and is discharged to the house sewer. In another system, gar-

bage is collected as before but dumped into large, centrally

located garbage grinding stations that discharge garbage to the

municipal sewerage system. In small communities, the gar-

bage grinding station may be located at the sewage-treatment

plant. The strength of the sewage is increased and additional

sludge digestion and drying facilities will be required when a

large amount of garbage is handled.

Disposal at Sea Where dumping at sea is practiced, all gar-

bage and other refuse is dumped into large garbage scows or

barges. The scows are towed by tugs and the garbage is taken

out to sea and dumped a suffi cient distance out to prevent the

refuse being carried back to shore and causing a nuisance.

Bad weather conditions hamper this operation and unless

this method is kept under very careful surveillance, abuses

and failures will result. Because of the cost of maintaining a

small navy and diffi culties in satisfactorily carrying out this

operation, coastal cities have reverted to sanitary landfi ll and

incineration. In recent years, consideration has been given

to the compaction of refuse to a density greater than 66.5

pounds per cubic foot prior to transport and then disposal

by burial in the ocean at depths greater than 100 feet, based

upon oceanographic conditions, to ensure there will be no

mixing with surface water. More research is needed to deter-

mine stability of the compacted refuse and effect on marine

life. See High density compaction.

Garbage Reduction In the reduction method of garbage

disposal, the garbage is cooked under pressure. Fats melt

out and are separated from the remaining material. The fat

is used in the manufacture of soaps or glycerines and the

residue is dried, ground, and sold for fertilizer or cattle feed.

Odor complaints are associated with this process and, where

a solvent such as naphtha is used to increase the extraction

of fat, a greater fi re hazard exists. The use of synthetic deter-

gents and chemical fertilizers and high operating costs have

led to the abandonment of this process.

Composting Composting is the controlled decay of organic

matter in a warm, moist environment by the action of bacte-

ria, fungi, molds, and other organisms. This may be an aero-

bic and/or anaerobic operation. Moisture is maintained at

40–65%, 50–60% is best. Composition of the refuse, disposal

of refuse not composted, demand for compost and salvaged

material, odor production and control, public acceptance and

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