ENCYCLOPEDIA OF ENVIRONMENTAL SCIENCE AND ENGINEERING - MANAGEMENT OF SOLID WASTE pot

Hazardous wastes, as defined by Federal and State regulation, generally are managed outside the munici-pal solid waste stream.. Exceptions are household hazardous wastes and hazardous wa

INTEGRATED WASTE MANAGEMENT

The most recent comprehensive document produced by the

federal government characterizes the materials commonly

referred to as “municipal solid waste” (“MSW”) as follows:

“ residential solid waste, with some contribution

from commercial, institutional and industrial sources In

some areas, nonresidential wastes are managed separately,

largely because industrial and some commercial sources

produce relatively uniform waste in large quantities, which

makes them more suitable for alternate disposal techniques

or recycling Hazardous wastes, as defined by Federal and

State regulation, generally are managed outside the

munici-pal solid waste stream Exceptions are household hazardous

wastes and hazardous wastes generated in very small

quan-tities, which are often placed in the municipal solid waste

stream by the generator.” 1

One of the most significant developments in municipal

solid waste is the growing acceptance by citizens, all levels

of government, and industries of a new overall philosophy

concerning the management options available to address the

problem of increased waste generation in the face of

ever-decreasing land disposal sites This philosophy is commonly

known as “integrated waste management” and involves the

reliance upon a hierarchy of options from most desirable to

least desirable The options are as follows:

Source reduction, limitation of the amount and/or

toxicity of waste produced

Recycling, reuse of materials

Incineration, thermal reduction

Sanitary landfill, land disposal

While this hierarchy is little more than a common sense

approach to municipal solid waste problems and the unit

operations represented are not new, emphasis on the source

reduction and recycling options as preferred represents a

pro-found shift in attitudes toward municipal waste management

The traditional perspective that generators could produce

dis-cards without limit and depend on technological approaches

to mitigate such wastes and any associated effects of

treat-ment is no longer acceptable This approach is not unique

to the solid waste area but is a part of federal and state

“pol-lution prevention” strategies, which emphasize avoidance of

all types of pollution as preferable to “end of pipe” and other

traditional methods of environmental regulation

LEGISLATION

In 1984, amendments were made to the Resource Conservation and Recovery Act of 1976 (“RCRA”), the existing federal legislation covering solid waste management Although the majority of these amendments were concerned with the regulation of hazardous waste as were the original RCRA mandates, some changes and additions were made to those provisions which were directed at nonhazardous waste

The U.S Environmental Protection Agency (“EPA”) was directed to determine whether the existing criteria for land disposal of waste previously promulgated pursuant to Sections 1008(a) and 4004 of RCRA are adequate to protect human health and the environment from groundwater con-tamination and whether additional authorities are needed to enforce them In addition, EPA must revise the criteria for those facilities which may receive hazardous household or small quantity generator waste Furthermore, States were given three years to develop a program to ensure that munici-pal facilities met the existing criteria and the revised crite-ria when they are promulgated Although enforcement is still largely a state matter, EPA is empowered, though not required, to enforce the criteria if states fail to comply with their obligations As of this writing, revised criteria have been proposed but not yet adopted. 2

Perhaps the most significant aspects of the federal law and its implementation involve initiatives with legislative roots in the original RCRA legislation which had historically received less attention than the Act’s mandate to establish a hazardous waste management regulatory system EPA has begun pursuing a number of activities such as conservation

of virgin materials through guidelines establishing revised product specifications and similar initiatives

State legislation has also witnessed a marked shift toward more conservation-oriented management schemes as well as stricter standards for processing and land disposal facilities

For example, at least twenty-four states have laws mandating the use of recovered materials in procurement processes As

of this writing, nine states had legislation requiring deposits

on beverage containers and four states had mandatory cling laws covering a wide range of materials The scope of these new legislative initiatives and the myriad of options and alternatives they entail is beyond the purview of this analysis What is apparent, however, is that source reduction and recycling represent an important part of modern waste management systems

3) Disposal (or, hopefully, reuse)

Another natural division, resulting in part from the current

reg-ulatory states, is between hazardous and nonhazardous wastes

This section will deal primarily with nonhazardous wastes;

specifically, with their source and composition and disposal

However, a brief discussion of hazardous wastes is included

because of their importance in understanding the management

of urban waste More detailed discussion of hazardous waste

is found in another section The important problem of

collec-tion is also left to a special seccollec-tion on that subject

Solid waste used to be considered any solid matter which

was discarded as no longer being useful in the economy

During the last decade, this definition has been considerably

broadened For regulatory, and usually disposal purposes,

solid waste is now defined as “any garbage or refuse, sludge

from a waste treatment plant, water supply treatment plant,

or air pollution control facility, and other discarded

mate-rial, including solid, liquid, semi-solid, or contained gaseous

material resulting from industrial, commercial, mining, and

agricultural operations, and from community activities, but

does not include solid or dissolved materials in domestic

sewage, or solid or dissolved materials in irrigation return

flows or industrial discharges which are point sources.” 3 This

definition is important because it indicates that all matter

which is disposed of onto the land in any form is considered

“solid waste.” In addition that material which causes or

sig-nificantly contributes to an increase in mortality or serious

illness or poses a substantial hazard to human health or the

environment, is considered a “hazardous waste.” Hazardous

wastes have been further defined by rulemaking to a limited

set of materials and criteria such as toxicity, flammability,

reactivity, or corrosivity. 4 The handling of hazardous waste

requires special care and special permitting Contrary to the

management of normal refuse or solid waste, the generators,

transporters, and disposers of hazardous wastes must meet

stringent federal and state criteria and have considerable

potential liability exposure The disposers of solid waste

which is not hazardous must meet state criteria that are not

nearly as stringent as those for hazardous materials Thus,

while hazardous material in the past has been often disposed

of along with all other refuse, today this is no longer the case

Industrial waste generators segregate their hazardous from

their industrial waste so as to minimize their problems

Solid wastes are one of the three major interacting waste

vectors; the others are air and water pollutants Solid wastes,

if improperly handled, can be a source of land, air and water

pollution They are, also, at this writing, one of the most

vol-atile public issues and a problem which is presenting many

communities with significant institutional challenges

Significant progress has been made in regulating the posal of solid waste over the last decade Open dumps which presented aesthetic as well as environmental challenges are for the most part closed Regulations are in place for managing solid wastes in an acceptable manner However, dumping into the ocean, which can create “dead” zones, hopefully will be eliminated Nor have we eliminated the potential problems of leachate from landfills Perhaps the most significant problem is the one of locating new landfills or substituting resource recov-ery, reuse and recycling capacity for landfill disposal The technologies are available, but the economics still favor land disposal In the early ’70s there was great hope for massive resource recovery and recycle projects Some of those, dis-cussed later in this section, have not come to fruition because

dis-of economic and institutional barriers Others have succeeded but the technology has not been spread, primarily because of economic barriers Individual and community action to reduce the amount of wastes generated and collected has, in many areas of the country, been successful For example, solid waste contains significant amounts of valuable material; 40% to 50%

of urban waste is paper and, if recycled, can replace virgin stock equivalent to about 9 trees per person per year In addi-tion, the community and thus the taxpayer also saves in terms

of lower collection and disposal costs However, this is still

of limited application because it is usually limited to pers, aluminum cans and perhaps glass Both technology and institutional methodologies for recycling solid waste are still in their infancy and must gain momentum if we are to meet the challenge of solid waste management in the years to come

REGULATION OF SOLID WASTE MANAGEMENT

Regulation of solid waste management has been scattered

The federal government, contrary to its prior policies in air and water, did not take a strong posture in solid waste management

It left regulatory initiative to the states and localities These dealt with the solid waste management primarily through the licensing of collectors, through the “Utility Commissions”

and adding to zoning ordinances regarding local landfills

Public health regulations also played a role with respect to reduction of rodents and pests at landfills Air emissions from incinerators were regulated as were wastewater discharges

In the last several years a number of states have enacted and implemented legislation to regulate landfills Probably the earliest and still among the most comprehensive is the regu-latory effort of the State of California which has classified landfills which respect to underlying geological conditions in terms of what a landfill can and cannot accept

A comprehensive solid waste law at the federal level was passed in 1976 as the “Resource Conservation and Recovery Act of 1976.” 5 This act provides for federal assis-tance to states and regions developing and encouraging environmental sound disposal of solid waste and the maxi-mum utilization of resources It calls for state and regional plans and for federal assistance to develop these plans It requires that each plan shall prohibit the establishment

of open dumps and provides for the upgrading of open

dumps that are currently in use It also requires that

crite-ria for sanitary landfills be established However, it leaves

enforcement to the states At the same time, the Act under

Subtitle C provides for federal regulation of the

manage-ment of Hazardous Wastes Many of these regulations have

been issued but the critical ones covering treatment,

stor-age and disposal facilities are still under review

SOURCES OF WASTE

Solid waste differs from air and water pollutants in that it

comes in discrete quanta and is very heterogeneous in nature

Both composition and rate vary significantly from day to day

and from season to season as well as from otherwise similar

sources

The solid waste production in the United States is in excess

of four billion tons/year and was expected to increase to five

billion tons by 1980. 6 Table 1 breaks this down for the year

1967 by major source However, waste generation appears to

have stabilized despite increased loads from air and water

pol-lution control facilities How long this will last remains to be

seen, if and when significant conversions to “coal as fuel” and

more stringent air and water pollution control take place

Urban Waste

Urban waste collected is between 4 and 8 lbs per person per

day, with typical values lying between 4.5 and 5.5 lbs per day

This differs from the amount generated because of self and

private disposal The major wastes included in this category

are tabulated in Table 2, which includes a summary of disposal

trends One should be careful in the terminology because often

domestic and municipal are used interchangeably to indicate

the total refuse picked up from residential (domestic),

institu-tional, small business and light industrial sources

Some further definition of terms may be useful at this

point In general usage many of the terms have been used

interchangeably However, an effort to standardize the

ter-minology was made by the Institute for Solid Waste of

the American Public Works Association and the Office of

Solid Waste Management of the Environmental Protection

Agency. 7 The standard usage of terms detailed by these

groups is summarized here:

Refuse All solid waste matter

Garbage The animal and vegetable waste resulting

from the preparation of food

Rubbish The waste from homes, small businesses,

and so on excluding garbage

Trash Used equivalent to rubbish

Litter Street refuse

Industrial Waste Specialized refuse from

manufactur-ing plants, and usually excludes rubbish

Domestic waste composition will vary seasonally, as well as

with locale and economic status Typical analyses for

domes-tic plus municipal refuse are shown in Table 3 As can be

seen in a comparison of the data, the composition has not

changed drastically with time except for a significant tion in ash because of the change from coal as a home heat-ing fuel Location variations noted are as great or greater A study of seasonal variations made in 1939 for New York City also showed greater variations: the ranges were garbage, 44 to 3.5%; and metal, 11.6 to 3.1%. 8 Base data have been difficult

reduc-to obtain because of the many variabilities in the base The most significant variables include the economic level of the area, the ratio of commercial to residential property, the type

of commercial establishments and the housing density and age The entire picture on obtaining accurate data on urban and/or domestic refuse is further complicated by the sampling problem A discussion of this problem is beyond the scope of this work; the reader is referred to some basic work in this area

by Carruth. 9 An excellent review of sampling and testing has been prepared by the Institute of Solid Wastes. 10 Further work

is being done in this area by ASTM’s D-34 Committee

The ultimate chemical composition of municipal refuse has been examined by a number of investigators Table 4 gives the range of values to be expected Recently 0.3 to 0.5% chloride has been found in refuse independent of the presence of poly-vinyl chloride; this is due to the presence of salt primarily. 11

Density of municipal refuse varies with the load applied to

it Typically household refuse has a density of 350–400 pounds per cubic yard Transfer stations and/or landfill operations can compact it to between 500 and 800 lbs per cubic yard depend-ing upon the material and conditions The effect of compres-sion on density for the Chandler, Arizona refuse is shown in

Figure 1 High pressure compaction (see Compaction) can increase the density to 1200 to 1400 lbs per cubic yard

Industrial Wastes

Industrial wastes amount to about 115 million tons annually

They include any discarded solid materials resulting from an

TABLE 1 Major sources of waste matter United States 1967 5

Source

Solids generated lab/cap/day Million tons/yr Urban

industrial operation or establishment with the exception of

dissolved or suspended solids in domestic or industrial waste

waters The composition and quantity of industrial solid

wastes vary significantly from location to location, as well

TABLE 2 Composition of wastes from urban sources 6

Urban sources Waste Composition Disposal, present

Domestic Garbage Wastes from preparation, handling and sale of

food Rubbish, trash Paper, wool, excelsior, rags, yard trimmings,

metals, dirt, glass, crockery, minerals Landfill Ashes Residue from fuel and combustion of solid wastes Incineration Bulky wastes Furniture, appliances, rubber tires Dumping Commercial Garbage Same as domestic Landfill

Institutional Rubbish, trash Same as domestic Incineration

Ashes Same as domestic Demolition wastes, urban

renewal, expressway

Lumber, pipes, brick masonry, asphaltic material and other construction materials

Dumping Landfill Construction wastes Scrap lumber, pipe, concrete, other construction

materials

Dumping Landfill Open burning Special wastes Hazardous solids and semiliquids, explosives,

pathological wastes, radioactive wastes

Burial, incineration Special

Municipal streets, incinerators, sewage

treatment plants, septic tanks

Street refuse Dead animals Abandoned vehicles Fly ash, incinerator residue, boiler slag Sewage treatment residue

Sweepings, dirt, leaves Cats, dogs, horses, etc.

Unwanted cars and trucks Boiler house cinders, metal scarps, shavings, minerals

Solids and sludge

Fill Bury or incinerate Reclaim Landfill or dump Landfill

—

0 20 40 60 80 100 100

300 500 700 900 1100 1300

APPLIED LOAD, LBS./SQ IN.

FIGURE 1 Refuse density Household refuse, Chandler,

Ariz., 1954 Credit: APWA, Municipal Refuse Disposal; 1966

as between industries and within a given industry Table 5

lists the type of wastes to be expected from the various SIC Industrial Groups A large fraction of the wastes are generally common to most industries and are listed on Table 6 Data on the amounts of waste generated by or collected from various industries is very limited Industry, quite natu-rally, has considered this type of data confidential in that it often reveals significant process and economic information

Average data, even if available, are of limited value because wide variations can result from process differences, process efficiencies and direct recycle, as shown in a study based on detailed interviews The results of this study giving total waste

by industry are summarized in Table 7 Industry waste duction on a unit per employee basis vary widely and are sum-marized for large and small companies in Tables 8 and 9 Increased efficiency as well as new uses for present indus-trial waste streams will alter both the quantity and composition

pro-of the material for disposal in the next decade For example, saw mill waste is being reprocessed into composition board and this utilization could essentially eliminate this waste stream Only limited projections can and have been made and these show only a reduction in saw mill wastes. 12 Conversely, enforcement of air pollution statutes will increase the amount

of potential solid wastes significantly Greater purification of industrial wastewater will also affect the solid waste load

Agricultural Wastes

Agricultural wastes are principally organic as indicated in

Table 10 The exceptions are chemicals used in various facets

of farming such as pesticides, containers, and small amounts

Material Paper and paper prod 56.01 53.5 32.71 53.33 56.5 42.7 50 69.0 c 69.7 c 38

a Included in glass and leads.

b Glass averaged 6.4% range 3.5–9.3%.

of miscellaneous waste matter resulting from maintenance

and general housekeeping

Most crop waste is either plowed back into the soil or

composted Some open burning takes place In some special

cases such as bagasse (sugar cane stalks) industries have been

established to utilize the waste material Essentially none of

this material finds it way into the usual disposal facilities

Animal wastes pose a different problem because much

is produced in very concentrated areas such as feed lots

or poultry farms The disposal of these wastes is posing a

greater problem than crop waste, but may be more easily

solved because it is concentrated and therefore susceptible

to processing without collection Average waste yields for a

variety of domestic animals are summarized on Table 11

Mineral Wastes

Mineral wastes including solids generated in mining, milling

and processing industries are expected to reach between two

and four billion tons per year in 1990 In 1965 this waste

amounted to 1.4 billion tons, as summarized in Table 12

Hazardous Wastes

Hazardous wastes as defined by the federal government and

in many cases similarly by the states, must be receiving

spe-cial handling These wastes generally include materials that are

injurious to human health, toxic, can cause irreversible

environ-mental damage, such as high concentrations of pesticides, are

corrosive, reactive (form toxic gases), or highly inflammable

These wastes are defined in Federal Regulations (40CFR261)

They require special management from generation through

treatment and disposal as defined again by Federal Regulations

A detailed discussion of Hazardous Waste Management is

cov-ered in a section on Hazardous Waste

Processing Methods

A variety of processing methods, as summarized in Table 13, are available at present for handling solid wastes Most have been in use in some modification for at least the last 50 years

The choice of processing method will depend not only on the type of waste but also on location, sources, quantity of waste, method of collection, public opinion, and ultimately economics

Solid waste management was a 4.5 billion dollar try in 1968 It is only in recent years that the public has begun to worry about disposal of solids Prior to that it was

indus-“out-of-sight, out-of-mind.” With ever growing amounts of solid waste as detailed in the discussion on sources, and con-cerns about pollution of ground and drinking water as well

as release of hazardous materials, public pressure is ing a major factor in any decision on waste management

The major disposal methods in use are landfill and eration Of potential interest in the United States are high pres-sure compaction and reclamation by recycling Recycling is being used, but requires solution of institutional and techno-logical barriers before becoming a major factor Compaction

incin-is utilized in at least one major facility in the Meadowlands in New Jersey Composting is practiced in Europe, but also has not been successfully applied in the United States although it does have potential There are new processes and techniques appearing for waste disposal and for the first time an organized research and development effort was mounted in the early ’70s

to look at solid waste disposal; it has slowed down but there is ample opportunity for further progress

Disposal methods could be discussed from the point

of view of source: a brief summary of the most used ods for a variety of sources may be found in Table 14 This discussion will instead focus on the disposal methods most commonly in use today, landfill and incineration, followed

meth-by discussion of compaction, composting, and some of the newer disposal techniques

The oldest method of disposal is dumping either on land

or sea Here dumping in distinguished from Sanitary Landfill (see below) Dumping costs between $6 and $10 per ton and has been used for all waste materials It is totally unsatisfac-tory for putrescible materials such as food wastes and unsatis-factory from a public health as well as aesthetic and land use viewpoint, even for inert material such as demolition waste

Open burning is often used for demolition waste, tree branches and stumps, and similar items; it is unacceptable because of the air pollution it creates Neither dumping nor open burning have a place in the modern waste disposal scheme and are illegal

Sanitary Landfi ll

Landfill is the most widely used method of waste disposal

There are 8900 authorized sites (about half publicly ated) used by the 6300 communities surveyed in 1968. 14 There appeared to be an equal number of unauthorized dumps Unfor-tunately only 6% of the sites were considered to be “truly”

oper-sanitary The remainder fell either into Category B or C on the

US Public Health Service Classification Scale, summarized in

TABLE 4 Municipal refuse B ultimate chemical analysis Constituents % by weight (as received) Proximate Analysis —

Moisture 15–35 Volatile matter 50–65 Fixed carbon 3–9 Noncombustibles 15–25 Ultimate analysis — Moisture 15–35

Nitrogen 0.2–1.0 Sulfur 0.02–0.1 Chloride 0.3–0.5 (16) Noncombustibles 15–25 Heating values, Gross 3000–6000 Btu/1b

TABLE 5 Sources and types of industrial wastes SIC group classification Waste generating process Expected specific wastes

Plumbing, heating, air conditioning

Special trade contractors

Manufacture and installation in homes, buildings, and factories

Scrap metal from piping and duct work; rubber, paper, and insulating materials, miscellaneous construction and demolition debris

Ordnance and accessories Manufacturing and assembling Metals, plastic, rubber, paper, wood, cloth, and

chemical residues Food and kindred products Processing, packaging, and shipping Meats, fats, oils, bones, offal, vegetables, nuts and

shells, and cereals Textile mill products Weaving, processing, dyeing, and shipping Cloth and fiber residues

Apparel and other finished products Cutting, sewing, sizing, and pressing Cloth and fibers, metals, plastics, and rubber

Lumber and wood products Sawmills, mill work plants, wooden container,

miscellaneous wood products, manufacturing

Scrap wood, shavings, sawdust; in some instances metals, plastics, fibers, glues, sealers, paints, and solvents

Furniture, wood Manufacture of household and office furniture,

partitions, office and store fixtures, and mattresses

Those listed under Code 24, and in addition cloth and padding residues

Furniture, metal Manufacture of household and office furniture,

lockers, bedsprings, and frames

Metals, plastics, resins, glass, wood, rubber, adhesives, cloth, and paper

Paper and allied products Paper manufacture, conversion of paper and

paperboard, manufacture of paperboard boxes and containers

Paper and fiber residues, chemicals, paper coatings and fillers, inks, glues, and fasteners

Printing and publishing Newspaper publishing, printing, lithography,

engraving, and bookbinding

Paper, newsprint, cardboard, metals, chemicals, cloth, inks, and glues

Chemicals and related products Manufacture and preparation of organic chemicals

(ranges from drugs and soups to paints and varnishes, and explosives)

Organic and inorganic chemicals, metals, plastics, rubber, glass, oils, paints, solvents and pigments Petroleum refining and related

industries

Manufacture of paving and roofing materials Asphalt and tars, felts, asbestos, paper, cloth, and

fiber Rubber and miscellaneous plastic

products

Manufacture of fabricated rubber and plastic products Scrap rubber and plastics, lampblack, curing

compounds, and dyes Leather and leather products Leather tanning and finishing: manufacture of leather

belting and packing

Scrap leather, thread, dyes, oils, processing and curing compounds

Electrical Manufacture of electric equipment, appliances, and

communication apparatus, machining, drawing, forming, welding, stamping, winding, painting, plating, baking, and firing operations

Metal scrap, carbon, glass, exotic metals, rubber, plastics, resins, fibers, cloth residues

Transportation equipment Manufacture of motor vehicles, truck and bus bodies,

motor vehicle parts and accessories, aircraft and parts, ship and boat building and repairing, motorcycles and bicycles and parts, etc.

Metal scrap, glass, fiber, wood, rubber, plastics, cloth, paints, solvents, petroleum products

Professional, scientific controlling

Miscellaneous manufacturing Manufacture of jewelry, silverware, plated ware, toys,

amusement, sporting and athletic goods, costume novelties, buttons, brooms, brushes, signs, and advertising displays

Metals, glass, plastics, resins, leather, rubber, composition, bone, cloth, straw, adhesives, paints, solvent

Stone, clay, and glass products Manufacture of flat glass, fabrication or forming of

glass: manufacturer of concrete, gypsum, and plaster products; forming and processing of stone and stone products, abrasives, asbestos,and miscellaneous nonmineral products.

Glass, cement, clay, ceramics, gypsum, asbestos, stone, paper, and abrasives

Primary metal industries Melting, casting, forging, drawing, rolling, forming,

and extruding operations

Ferrous and nonferrous metals scrap, slag, cores, patterns, bonding agents

Fabricated metal products Manufacture of metal cans, hand tools, general

hardware, nonelectric heating apparatus, plumbing fixtures, fabricated structural products, wire, farm machinery and equipment, coating and engraving

of metal

Metals, ceramics, sand, slag, scale, coatings, solvents, lubricants, pickling liquors

Machinery (except electrical) Manufacture of equipment for construction, mining,

elevators, moving stairways, conveyors, industrial trucks, trailers, stackers, machine tools, etc.

Slag, sand, cores, metal scrap, wood, plastics, resins, rubber, cloth, paint solvents, petroleum products

Table 15 There are additional classifications with respect to

use in force in California and suggested in the new Federal

Regulations. 15 There is an increase in “Sanitary Fills” and an

elimination of “Dumps.”

Sanitary landfill is an acceptable method of disposal of

solids and provides for the ultimate disposal of many types of

waste; exceptions are non-degradable materials such as plastic

or aluminum which are placed in landfills Other items

mate-rial, toxic chemicals, and hazardous materials, are not allowed

in landfills for safety Where land is plentiful, or marginal areas

are available for reclamation, sanitary landfills offer a number

of advantages over other disposal methods including low

ini-tial and operating costs Other advantages and disadvantages

are summarized in Table 16 Sanitary landfill is basically the

dumping of wastes followed by compaction and the daily

application of an earth cover This situation has improved in

the last decade and by the mid-1980s—all landfills will be sanitary Several techniques are available, some of which are depicted in Figure 2, depending on the type of site available

The one constant in all operations is the daily earth cover, erably a sandy loam, amounting to, usually, one part earth for every four parts refuse Another, which is being required in new landfills, is leachate collection and treatment In addition these types of waste disposal are limited to “non-hazardous”

pref-materials unless the landfill is especially constructed, licensed and managed

Proper site selection is as critical to a satisfactory fill as is sound operation Selection criteria include proper ground and surface water drainage and isolation as well as leachate collection and treatment, to prevent pollution of the ground water table Location in a drainage basin near streams or lakes and in or close to the ground water table present special problems and should be avoided, where pos-sible Placement in the 100 year flood plain is prohibited

land-Accessibility of cover material is an important consideration

The use of tidal areas and marshes is prohibited Dry pits, abandoned quarries and certain types of canyons of depres-sions are often satisfactory landfill sites

The size of landfills is often restricted by the amount

of land available The capacity can be estimated with a fair degree of accuracy Refuse on arrival may vary in density from

300 to 800 pounds per cubic yard, depending on the delivery method Typically the density in the “fill,” of the initial com-paction with a typical crawler tractor will be 1000 lbs/yd for

a single lift (layer) with a depth of 20 feet of less For tiple lifts the initial density can reach 1250 lbs/yd This initial loading increases by as much as 50% over a period of time as further compaction and decomposition takes place. 16

Much of the material in the sanitary landfill decomposes over a period of between three and ten years depending on climate, permeability of the cover, composition of the refuse and degree of compaction The decomposition in sanitary landfills is anaerobic as compared to aerobic degradation often found in other types of fill Temperatures typically reach 120°F in the fill as a result of the degradation The principal gas products are carbon dioxide and methane The greatest gas production takes place in the first two years, according

to a study made at the University of Washington Ammonia and hydrogen sulfide are not problems in sanitary landfills although small amounts of these gases are produced Odors resulting from the decomposition of putrescible material can

be controlled by observing good operating practice; that is, covering the fill continuously and sealing surface cracks Fire hazard and insects and vermin are not a problem, as compared

to dumps, in a properly operated sanitary landfill although chemical control of the latter two is sometimes required

Completed landfills are suitable for use as recreational facilities, airfields and parking areas; light industrial build-ings may be erected on landfill Building of residential structures on fill requires special precautions because of the potential hazards associated with the evolution of methane and other decomposition gases

The cost of operating a sanitary landfill makes it an tive means of disposal where land is available Costs for a

attrac-TABLE 6 Solid wastes common Packing materials fiber

metal paper plastic wood Maintenance materials paints

metal grease plastic rags General housekeeping waste paper

fires glass solvents industrial chemicals

TABLE 7 Industry Waste for disposal thousand tons/yr

sanitary fill will vary between $3 and $10 per ton, depending

on location and size of the fill Small fills, handling less than

50,000 tons per year, will have a unit cost of $5 to $10 per

ton A large urban fill more typically shows costs of $3 to

$6 per ton The wide variation is a result of location differences,

which include differences in land acquisition costs, labor costs

and operating differences due to local surface conditions and

requirements

The use of landfill will continue; however, its future,

par-ticularly in densely populated urban areas, is in doubt Land is

at a premium for this type of application close to urban centers

What land is available must be preserved for non-combustible

material and ashes For examples, one urban county in New

Jersey has less than three years landfill capacity available and

in portions of Long Island no more land for landfill is available

Hauling costs too, as well as public resistance in more rural

areas is making landfill less attractive for urban areas such as

metropolitan New York Finally, landfill does not provide for

maximizing the value of refuse as a source of raw materials

Recent studies to find alternatives to traditional landfill practices include a demonstration of shredding prior to fill-ing Only domestic refuse was shredded; the product was a superior fill compared to “raw” refuse It could be left uncov-ered with satisfactory sanitary and aesthetic results and was easier to dump and compact Flies and rats did not breed on the shredded refuse

The compacted, uncovered fill also had better weathering and load bearing characteristics This can be achieved at a cost

of about $5.00 per ton in a 65,000 ton per year operation. 17

The method has some attractive features, and some cial facilities including one in Monmouth Country, NJ, which incorporates some recycle, use this principle However, oper-ating and investment costs do appear to be higher than the more traditional method of filling “raw,” as collected, refuse

Baling of refuse may be particularly attractive where landfill sites are not locally available A feasibility study was carried out in Chicago which showed that this method overcomes many of the present objections to landfill The

TABLE 8 Waste generation for large fi rms 13

Industrial classification

Employment 1 a Annual wastes vol Cu yd 2 b Annual wastes per employee cu yd 3 c

Title Ordnance and accessories 29,356 131,404 4,476

Other food processing (except 203) 2,012 17,545 8,720

Apparel 601 1,248 2,077

Paper and allied products 250 9,360 37,440

Printing, publishing and allied 968 7,020 7,252

a Column 1: Data on employment were obtained for those large firms which were surveyed and included in the wastes calculation from the research

department of the Association of Metropolitan San Jose (Greater San Jose Chamber of Commerce).

b Column 2: FMC report, Solid Waste Disposal System Analysis (Preliminary Report), Tables 10 and 11, 1968 [5]

c Column 3: Column 2/Column 1.

d For Canning and Preserving (SIC 203), no individual firm data were available The industry total developed for the county as a whole was divided by the

total employment in the industry (specially tabulated) to arrive at the multiplier See text for further explanation.

e Data not available.

Japanese have been leaders in this area using high pressure

presses to provide solid cubes suitable for use in building new

land in tidal areas A facility is being successfully operated

in New Jersey More details may be found in the discussion

of compaction

Incineration

Incineration is essentially a method for reducing waste volume

and at the same time producing an inert, essentially

inor-ganic, solid effluent from material which is largely organic

Typical feed analyses are shown in Table 4 In addition to the

solid product a gas is produced consisting mainly of CO 2 , H 2 ,

O 2 and N 2 but containing other gaseous components in tract

quantities depending on the type of material burned and the

operating conditions Incineration is not an ultimate disposal

method in that the solid residue which is primarily an ash

containing some metal must still be disposed of, usually as

landfill The primary advantage is that it reduces the volume

to be disposed of and results in a “clean” inert fill For every

100 tons of material fed to the incinerator approximately

20 tons of residue result The volume reduction is even more

significant, often resulting in a 90% lower solids volume for

organic materials

The theory of incinerator operation is very simple A unit

is designed to expose combustible material to sufficient air at

high temperature to achieve complete combustion Combustion

is usually carried out in fuel beds to ensure good contact of air and refuse Several types of configurations are used to achieve contact; these include concurrent flow of fuel and air-underfire, countercurrent flow of fuel and air-overfire, flow of fuel and air at an angle to each other—crossfeed; and combinations of these The combustion is basically the same for all methods

in that at the ignition front oxygen is rapidly consumed in the reaction O 2 ⫹ C → CO 2 and if oxygen is depleted CO 2 ⫹ C →

2CO Therefore, sufficient oxygen must be available to obtain complete combustion; usually this is provided by adding addi-tional air in the chamber above the fuel Incinerators are typi-cally operated with about 50 to 150% excess air in order that the gas temperatures do not drop below that required for good odor-free combustion; this is usually in the 1700–2300°F range

Recent trends have been to go to the higher part of this range while old units often operate at 1600°F or below The effect of excess air on gas composition is summarized in Table 17 for

a typical refuse A detailed discussion of typical air ments and their effect on the thermal balance may be found in Principles and Practices of Incineration. 18

Trace components in the incinerator-start gas include some SO 2 and NOx The former depends on the sulfur in the refuse and is typically around 0.01 to 0.02% Nitrogen oxide

is generally formed in combustion processes and depends on the amount of excess air and to some degree the operating temperature of the incinerator Typical values of two pounds

of equivalent NO 2 per ton of refuse have been reported. 19,20

TABLE 9 Waste generation typical for small fi rms 14

Industrial classification

Weekly wastes vol per firm cu/yd 1 a

Annual wastes vol per firm cu/yd 2 b

Average employment per firm 3 c

Annual wastes vol per employee cu/yd 4 d

Title

Canning and preserving 4 — (not surveyed) —

Other food processing (except

Paper and allied products 44.650 2,321.80 35.479 65.442

Printing, publishing and allied 6.448 335.29 13.289 25.230

a Column 1: Data obtained and calculated for each SIC on the basis of small firm questionnaire response supplied by FMC.

b Column 2: Weekly average in Column 1 multiplied by 52.

c Column 3: Average size of small firm estimated from the distribution of firms by employment size, supplied by the California

Department of Employment (Research and Statistics), San Francisco Office.

d Column 4: Column 2/Column 3.

e Data not available.

TABLE 10 12

Agricultural waste (1966)

Amount (million tons/yr) Crop residue Corn stalks, grain stubble, cull, fruit and vegetable, vines, rice hulls, bagasse,

tree prunings, etc.

552 Animal manure (paunch manure) Organic matter, protein, fat, carbohydrates, nitrogen, phosphorus etc 1.532 a

This is equivalent to 500 to 1000 ppm of NOx in the

off-gas depending on the refuse composition and the amount

of excess air Other trace components can be found in the

off-gas and air summarized in Table 18 Their presence or

absence is very much dependent on the type of refuse

incin-erated and the operating conditions

Particulate matter is also present in the stack gas and is

removed by the usual techniques discussed in the section on

Air Pollution Particulate loadings of 3 to 25 pounds per tonne

of refuse burned have been reported 21,22 Typically, particles

range from 5 to 350 microns in size with 30% by weight

under 10 microns and 75% less than 200 microns in size

Solids residue from incinerators will vary widely with the

type of feed and incinerator operating conditions Typical

resi-dues have been examined by the Bureau of Mines The results

of this work are summarized in Table 19 A typical ash and

slag chemical analysis may be found in Table 20 This residue

can be utilized in road fill or separated (see Reclamation)

Incineration can effectively be divided into local, onsite

and central methods The basic principles are the same but

the applications vary considerably Central incineration

facil-ities handle refuse from many sources and a wide variety of

feeds Local incinerators handle either special feeds, onsite,

such as industrial or hospital wastes, or serve a particular

small location such as an apartment house Size is not essarily a criterion although generally central incineration facilities have capacities in excess of 100 tons per day

At the present time there are about 200 central eration facilities in use (making this type of waste reduction facility the most prevalent one) Central incineration handled about 15 million tons of waste annually and is concentrated

incin-in the northeastern part of the United States It is also widely practiced in Europe The practice of incineration of wastes was growing as land for fill, particularly in urban areas, becomes scarcer and technological improvements provide more efficient and cleaner systems

A typical incineration facility will have a capacity ing from 100 to 1200 tons per day with individual furnaces usually limited to a 300 ton per day rating Most large incin-erators today are continuous-feed rather than batch design because operation is more controlled and easier In addition the absence of the heating and cooling cycle results in lower maintenance and a higher capacity per investment dollar Air pollution control is improved significantly in continuous-feed incinerators are compared to batch plants

A large central incineration facility is schematically shown in Figure 3.It can be divided into five areas: (1) the receiving section which includes the weight station, storage hopper and bucket crane; (2) the furnace—which includes the charging hopper, stokers, furnace chamber and air feed system; (3) the effluent gas treating facilities; (4) the ash handling system; and (5) the cooling water system The par-ticular system shown does not have provision for waste-heat recovery; only a few systems incorporate this at present

For mixed refuse, a typical refractory-wall incinerator will have 12.7 cubic feet in the primary furnace chamber and 18.5 cubic feet in the secondary chamber per ton of refuse per

24 hours with a grate loading of 77 pounds per square foot per hour Volume and loading requirements will vary with the type of feed as well as furnace configuration Typically the values quoted correspond to a 12,500 Btu per hour per cubic foot heat release A detailed discussion of furnace design is

TABLE 12 Generation by type of solid wastes from the mineral and fossil and fuel industries (1965)

Industry Mine waste Mill tailings

Washing plant rejects Slag

Processing plant wastes

Total (thousands

of tons) Copper 286,600 170,500 — 5,200 — 466,700 Iron and steel 117,599 100,579 — 14,689 1,000 233,877 Bituminous coal 12,800 — 86,800 — — 99,600 Phosphate rock 72 — 54,823 4,030 9,383 68,308 Lead-zinc 2,500 17,811 970 — — 20,311 Aluminum — — — — 5,350 2,350 Anthracite coal — — 2,000 — — 2,000 Coal ash — — — — 24,500 24,500 Other — — — — — 229,284 Total 419,571 288,900 144,593 23,919 40,233 1,146,500

TABLE 11 Unit generation rates Animal Waste (tons unit yr)

TABLE 13 Solid waste management methods Type Present usage Relative cost Items disposed of Principal benefits Sanitary landfill Most used (80%)

second largest method (4%)

High All burnable except

special items and over-sized items

Reduces volume, clean product can produce by- product items Open burning Illegal Low Construction

wastes, leaves, agricultural waste Compaction, high

pressure

Two plants in operation

Medium-high All except

hazardous materials

Produces dense, essentially inert blocks for fill Composting Very few Medium-high Organic only

No tires, large pieces

Provides soil conditioner Garbage grinding Large number home

units

High Organic only Reduces domestic

collections Dumping Not legal Lowest Non-putrescibles

Recycling Only for selected

materials and areas, increasing

High Selected

Depends

on process

Reduces quantity for ultimate disposal

a Many landfills are not sanitary but are included in this classification

b Low under $10/ton; Medium $10 to $30/ton; High $30 ⫹ ton

1

2

3 4

7) — final burning and settling chamber volume 8) — high-pressure opposed spray curtain 9) — fly-ash sluiceways

10) — sequential cyclone collectors 11) — induced-draft fan

12) — bypass flue 13) — provision for added filters or precipitators

beyond the scope of this work and the reader is referred to an

excellent work by Richard C Corey. 22

Incineration in the past has received a bad reputation

because of poor control of gaseous effluents and sloppy

han-dling of solid and liquid effluents With proper design and

operation an incinerator can meet or exceed requirements

on all effluent discharges A modern central incinerator is

a more complex operation than a large commercial steam boiler It therefore requires skilled operating, maintenance and supervisory personnel to ensure efficient operation

At the present time control of particulate matter in the effluent gas is the most critical problem in incinerator design