Management of solid wastes

10-4 Approaches for Consideration in Formulating Environmental Control Strategies In view of the particular importance of domestic solid wastes, typical composition, density, and calori

10.3.2 Normal Municipal Wastes

10.3.2.1 Recycling at the Source 10.3.2.2 Collection

10.3.2.3 Transport 10.3.2.4 Processing 10.3.2.5 Disposal 10.3.3 Junk-Auto Scrap 10.3.4 Sludges from Municipal Wastewater Treatment Plants 10.4 Management of Hospital Wastes

10.5 Management of Industrial Hazardous Wastes 10.6 Bibliography

10-2 Approaches for Consideration in Formulating Environmental Control Strategies

Waste is every substance or object, arising from human or animal activi- ties, that has to be discarded as useless or unwanted The above defini- tion encompasses an extremely heterogeneous mass of wastes, which may originate from people’s homes and from commercial or industrial activities

As the basis for subsequent discussions, it is useful to distinguish the

following two broad categories of wastes:

Municipal wastes include refuse normally generated from residences, from

the cleaning of public places, from construction and demolition, from commercial activities, from discarded bulky objects and cars,

as well as from numerous small industrial activities Waste sludges from municipal wastewater treatment plants are also included in this category

From the management point of view the categories of normal munici- pal wastes, junk automobile scrap, hospital wastes, and sludges from wastewater treatment plants will be considered

Hazardous wastes in the form of solids, sludges, or liquids typically

include wastes generated from services, such as hospitals, and

from industrial operations, such as industrial production pro-

cesses, or liquid waste and air pollution control installations The hospital wastes have been classified as hazardous ones by WHO because of their disease transmission potential Some industrial wastes exhibit ignitability and/or corrosivity and/or reactivity

and/or toxicity and are classified as hazardous (U.S, Federal

Register, May 19, 1980) Some are classified as hazardous because

Bank/WHO/UNEP, 1989)

Poor management of municipal solid wastes has an adverse impact from the aesthetic and the sanitary point of view The former cannot be neglected

in any society and particularly in touristic areas, where unsightly

conditions have detrimental economic consequences The latter is associated with air pollution (especially bad odours), with significant surface or underground water pollution from the leachates (see Table 4.2.2-5), and with health hazards for example, cholera, leprosy, pestilence, rabies, trachoma, typhus, viral hepatitis, etc, transmitted through vectors such as insects, rodents, dogs, cats, birds, and other animals:

The domestic fly lays eggs on warm and humid wastes The layva feed and grow on wastes thus becoming carriers of germs or enteric diseases, such as salmonella or shigella, which can infect fresh

or prepared food or even directly the lips of babies and small

children Cockroaches and numerous other species of insects play a similar rote

or bacteria-infected insects, such as fleas, to human habitat

Other animals feeding on wastes, such as stray dogs and cats, in addition to transmitting rabies, carry diseases, as well as

parasite insects (fleas) and arthropods (ticks or mites), which

are either vectors or passive carriers of disease

Other important adverse effects of improper management include forest

fires from spontaneous ignition of the emitted biogas (a product of the anaerobic decomposition of the organic matter in the wastes)

Poor management of hazardous wastes can result in short-term public health problems, as well as in environmental pollution Over the past 10

to 15 years the environmental authorities of industrialized countries have place considerable emphasis on this subject as they came to realize

that the related damage is often much more extensive than initially thought and that the cost to correct the "sins of the past" is much

higher in the long run For example, experience from the USA indicates that the cost of remedial measures are 10 to 100 times as much as those

of proper early management

lutions, the disposal of which, unless properly managed, simply trans-

fers the problem from one receiver to another, sometimes with longer lasting and more adverse consequences

is facilitated in practice by the use of appropriate tools In this book

a number of such tools are offered: :

tion about the nature of the solid wastes generated from various sources and allows assessment of their quantities In addition,

Tike the air and liquid waste inventory models of Sections 3.2.2 and 4.2.2, it defines the data requirements from field surveys

This model is thus a valuable tool in solid wastes inventory stud-

jes, not only for computing the waste loads and for defining their nature, but also for providing guidance on the data to be col-

lected during the field survey work, as well as for organizing and

presenting such data in a concise manner (see also Sections 5.2.3

existing land pollution problems

10-4 Approaches for Consideration in Formulating Environmental Control Strategies

In view of the particular importance of domestic solid wastes,

typical composition, density, and calorific data for various coun- tries, are listed in Table 5.2.2-1 Moreover typical properties

for individual municipal waste components are given in Table 5.2.2-2 enabling users to assess typical moisture content,

density, low calorific value and the quantities of residue left over after incineration on the basis of available waste composi-

tion data Table 5.2.2-3 provides data about the compaction ratio

of various types of solid wastes for alternative compaction

degrees enabling users to compute the landfill volume require-

ments, Section 10.3.2.5

10.3 Management of Municipal Solid Wastes

A well developed management plan views the entire waste generation, re- cycling, collection, transport, processing and disposal problem as a whole, striving, on one hand to provide an adequate level of public ser- vice and to satisfy the resource conservation needs, and on the other hand to minimize the system costs

The prevention of waste generation by promulgating "ecological"

products, by using proper packaging techniques, and by pre-planning product recycling and disposal from the design and manufacturing stages, ought to precede waste management efforts

However, in order to prevent waste generation, significant changes in consumer attitudes and in manufacturing production processes are re- quired Despite this, industrialized countries are currently focusing on this issue as the potential for environmental and economic rewards are significant and the need for resource conservation becomes ever more pressing

Mass production of cars that can be easily disassembled and recycled is

a good example of a new generation of products, which are designed so as

to minimize the quantity of final waste Obviously, the anticipated

short and medium term environmental benefits are extensive, but these kinds of changes are generally beyond the scope of the environmental engineer, Nonetheless, the use of environmentally safer products should

be encouraged, and the public can be convinced of their worth and

persuaded to buy them

The wrapping and packaging of products yields enourmous quantities of

waste and contributes significantly to the cost of the final product

Currently, discarded packaging materials constitute about 30 % of the

municipal wastes generated in industrialized countries, and 60 % of

these materials are associated with the sale of food and beverages

Management of Solid Wastes 10-5

Recent and forthcoming legislation in EC and in other countries include

incentives for lighter packaging, reused packaging, standardization of

packaging materials so as to facilitate their recovery and recycling,

and prohibition of "unfriendly" packaging materials that may create

problems during processing and/or disposal (e.g halogenated plastics)

\

10.3.2 Normal Municipal Wastes

In early societies the quantities of municipal wastes generated were limited, as the population densities were low, organic matter was deposited on land as fertilizer, and modern consumerism was absent This

may still be partially true in some regions, especially in the rural communities of the developing world, but the general picture is rapidly

changing

Indeed, the progressively improving standards of living, and along with

it the associated shortened product-obsolescence cycles and the wasteful consumer attitudes that develop, as well as the rapid urbanization, taking place in most countries, result in greatly increased quantities

of municipal wastes to be handled

The management of municipal wastes emerges thus as a problem of prime

importance and of considerable magnitude Moreover, as its solution generally rests with the Jocal authorities, it is not uncommon that a fair fraction of their operating expenditures is devoted for this pur-

pose For example, municipalities in Greece devote approximately 30 % of their total budget to solid waste collection and disposal

As the flowchart of Figure 6,3.2-1 illustrates, key elements in any in- tegrated municipal solid wastes management plan are the reduction of produced wastes through recycling at the source, waste collection, transport and processing (e.g through manual screening, and/or mechani- cal separation, and/or electromagnetic separation, and/or flotation, and/or composting and/or incineration), and finally the proper disposal

of the remaining refuse at a permanent storage site

10.3.2.1 Recycling at the Source

Home separation and recycling presents the greatest practical potential for the raduction of waste volumes and for the conservation of natural resources

10-6 Approaches for Consideration in Formulating Environmental Control Strategies

Transfer

Landfilling > Biogas

Basic Municipa? Solid Waste Management Steps and Alternative Approaches

Management of Solid Wastes 10-7

Returnable beverage containers (bottles and cans) through mandatory re- funds and/or deposits represent a system that is relatively easy to set

up and shown to be highly successful in both industrialized and develop-

ing countries Experience shows that over 90 % of the bottles and over

80 % of the cans are returned and that the average reuse cycles of the former vary from 10 to 20 times per container

Recycling of materials such as paper, aluminum, glass and plastic has

also been shown to be practical when these materials are separated at the source by the consumer Typical collection schemes are as follows:

Drop-off centres, strategically located so as to facilitate delivery by

the citizens, represent one of the most common type of collection system In these centres appropriate containers are placed, which are designed to receive the intended product (e.g white, coloured

and/or mixed glass; aluminum, iron and/or mixed cans; paper, cardboard and/or mixed paper etc)

Special trucks equipped with loader systems for lifting and empty-

ing the containers or for picking up the filled containers and re-

placing them with demountable empty ones, Figure 10.3.2.1-1, are

normally used to collect the recycled materials from the drop-off centres and carry them to temporary storage yards, to buy-back centres or directly to industries that will recycle them

Figure 10.3.2.1-1 Truck with flip-loader system picking up a waste-glass container with three

sections

Door to door collection of materials separated by the consumers can be

combined with the regular garbage collection, possibly with the use of special bins or piggyback trailers attached to the truck,

or can be accomplished using separate vehicles

10-8 Approaches for Consideration in Formulating Environmental Contro! Strategies

Combined collection is better suited to serve the general public

and has been successfully employed for recycling paper, as this can be achieved without having to provide home owners with special bins or bags Moreover, as the collection means are simple, ‘the

income from the recycled paper has been used in some places to provide incentives for the crew of the garbage truck Use of separate vehictes is better suited to serve relatively large producers of waste paper, aluminum or other materials, such as shopping centres, fast food shops etc

Separate collection of specific wastes, such as auto and truck tires or

yard wastes, allows their utilization while eliminating materials which may be troublesome at landfills Tires for example can be

used, after shredding, as raw material in the production of as-

phalt concrete or as a fuel in the production of cement, while

yard wastes can be composted

The disposal of lead-acid and household batteries along with do- mestic wastes is an issue that has drawn increasing attention over

the past few years as these batteries contain hazardous components such as lead, zinc, nickel, cadmium, mercury, copper, manganese, and lithium

Recycling of lead-acid (car) batteries so as to recover the lead

is a profitable operation and is practiced in many places Serious air and water pollution hazards are however associated with the

relevant processes and proper process and pollution control

systems are required In the U.S., 28 states prohibit the

disposal of acid-lead batteries along with the municipal solid

wastes, while 25 states have mandatory take-back provisions A

refundable deposit on lead-acid batteries, similar to that re-

quired for aluminum or glass containers, is gaining momentum: in

the U.S and appears to be becoming common practice

Household battery recycling programmes are usually designed to

collect all types of batteries, regardless of their toxicity

Recycling efforts directed at specific industries, hospitals, utilities, research establishments, or the military can be highly rewarding Moreover, the notion of placing a refundable deposit on

household batteries, is advocated as an alternative to voluntary battery collection

Waste reuse and recycling at the source is generally not profitable and

has to be supported by the interest of concerned citizens and possibly

government incentives Legislation making mandatory certain measures,

such as the refund and/or deposit for returnable beverage containers may

also be necessary The environmental rewards however are significant,

since recycling reduces the volume of the wastes to be handled,

conserves precious natural resources, and also lowers energy and water

consumption and generated air and water pollution by manufacturing

processes, Table 10.3.2.1-1

Management of Solid Wastes 10-9

Table 10.3.2.1-1 Energy and Water Consumption and Pollution Reduc-

tion Potential from the Use of Recycled Raw Mate- rials

Temporary storage represents the average person’s most intimate contact

with refuse and affects the collection method Containers of

various forms and sizes are used for this purpose, and a short de-

scription of these is given below:

Figure 10.3.2.2-1 Plastic bag, and dustbins of various sizes used for the temporary storage of do-

mestic garbage

10-10 Approaches for Consideration in Formulating Environmental Control Strategies

% Plastic bags either without any specifications, or-of certain specifications (for example DIN 55465), Figure 10.3.2.2-1;

% Plastic or metallic dustbins, typically with capacities in the

range of 120 to 370 It for domestic refuse, Figures 10.3.2.2-1, 10.3.2.2-3, and 10.3.2.2-4;

% Plastic or metallic containers moveable or fixed (depending on the type of collection vehicles employed) with capacities rang-

ing from 1,100 to 3,300 1t, Figure 10.3.2.2-2; and,

Figure 10.3.2.2-2 Typical metallic refuse container with a capacity of 1,100 ]†

# Large containers with capacities over 4 m3, periodically re-

placed with demountable empty ones, Figure 10.3.2.2-5 These containers are suitable for bulky objects, and for demolition,

construction, commercial and/or industrial wastes, and they can

also serve large residential complexes In the latter case at-

tention must be paid to maintain a reasonable distance between the containers and the residents

In urban areas waste can be stored near the pavement in front of

or behind the buildings, usually in plastic bags, trash bins, or

containers, or carried to specific public locations, and placed in

larger containers In small communities with populations of the order of 500, a single collection location may be justified

Collection methods depend on the temporary storage methods used and

include:

Management of Solid Wastes 10-11

% Manual collection of plastic bags with open vehicles, such as

conventional trucks, tractor/trailers systems or animal carts

Manual collection of the plastic bags and dust bins by special enclosed trucks providing compression through the use of screw, hydraulic, or paddle compactors, Figure 10.3.2.2-3;

Mechanical collection of dust bins and containers using rear-,

side-, double side-, front-, or front and side-loader trucks, Figures 10.3.2.2-4 These vehicles are capable of lifting and emptying one or two independent containers, have capacities ranging from 8 to 18 m, and provide waste compression ratios

from 1:3 to 1:6 Naturally, the containers in use must be com- patible with the collection system employed In this system provision must be made for the periodic washing of the contain- ers and special vehicles are required for this purpose

Mechanical replacement of large containers with empty ones us-

ing special trucks equipped with lifting mechanisms, Figure 10.3.2.2-5

Fiqure 10.3.2.2-3 Typieal manual collection with compacting collector trucks

10-12 Approaches for Consideration in Formulating Environmental Contro! Strategies

Figure 10,3.2.2=4 Typical mechanical collection with rear-loader truck, equipped with twin bin

flippers for 190 to 370 lt plastic bins

Rationalization of the waste collection system is of prime importance as

80 to 85 % of overall solid waste collection and disposal cost can be

attributed to the collection phase Solid waste Management studies

should not assume that wastes are collected and waiting for disposal,

but rather should include the waste collection phase

Rationalization of the collection system includes definition of the

level of service to be offered, a key element of which is the collection

frequency, analysis of the temporary storage and collection method to be

used, and optimization of the truck routing

Frequency of collection depends on the level of service to be offered,

on local climatic conditions and on other parameters, such as

waste composition It is generally established that once a week

pick up represents a minimum, and in certain situations adequate service In temperate climates with high putrescible content wastes, twice a week pick up may be necessary to prevent gross odours From the public health stand point it is desirable that

temporary storage of garbage not exceed 2 to 3 days, the time

required for fly larvae to mature In warm climates daily waste collection is considered preferable

The decision about collection frequency may also depend on other Parameters, such as the storage and collection system adopted (see

Management of Solid Wastes 10-13

below) Collection frequency substantially affects collection

aeons

YR i

TA

Figure 10.3.2.2-5 Typical collection of large container with commercial or industrial refuse

Storage and collection system rationalization does not yield the same

results for every study area, as the outcome depends on the area size and topography, on the size of buildings to be served, on the

available road space for the placement of containers and the

effective operation of collector vehicles, on traffic conditions, etc It depends also on the standard of living and the cost of labour in the study area

Door to door collection of plastic bags is a system that requires minimum organization, represents the lowest capital cost solution (as no containers are necessary and any type of vehicle can be used for collection), offers the greatest flexibility, especially

in congested areas with little space for the permanent placement

of containers, and is capable of adequately serving areas with small to medium size buildings On the other hand this system

presents a health hazard, as the wastes are exposed to animals,

does not permit mechanical collection, and inevitably results in increased collection frequencies (daily pick up schedules being typical), as households living in apartments have little space to

keep their filled bags inside till the next pick up date and take

them down to the road at unscheduled intervals Moreover, the safe use of this collection system requires strict control of stray animals

The use of standard garbage bins and/or larger plastic or metallic containers for pre-collection is preferable from the public health and aesthetic point of view, represents a low operating cost solu- tion as it is amenable to mechanical collection, and is better suited to serve commercial enterprises and large residential com-

10-14 Approaches for Consideration in Formulating Environmental Control Strategies

plexes However, the increased requirements for standardization,

organization, capital investment, as well as the reduced flexibil

ity, including road space requirements for the placement of

containers, of this solution have to be carefully weighed against the above advantages

According to some accounts, the labour requirements in man-hours per ton of garbage collected are about 2.5 for manual collection systems and 1.15 to 1.65 for mechanical collection ones The ne-

cessity of higher collection frequencies in the case of the manual collection system may be an additional important factor to

consider Based on the above figures, one can see that the Tow

cost of local Jabour favours the simpler tianual collection

methods, as the advantage of their low capital investment requirements tends to prevail In many developing and in most developed countries however, labour costs are relatively high and their contribution to the total collection cost emerges as

dominant For example, in the United States the direct and

indirect labour costs account for 60 to 75 % to the total Under such conditions the overall collection cost, defined as the sum of the capital investment and operating costs, tends to favour

mechanical collection systems Despite this, space or topography

limitations and/or simply organizational difficulties, are often

responsible for the continued use of manual collection systems

It should be borne in mind that the magnitude of the waste

collection system in urban areas is generally large and is not

amenable to easy experimentation Moreover, investment in the existing system can be substantial and thus the transition to a new system need to be gradual and carefully planned As a result, any changes should be carefully analysed jin terms of their suitability, cost, and acceptability to citizens

Collector truck routing rationalization involves definition of the way

the collector truck crews organize their work, as well as the

rationalization of the actual route the trucks will follow through the city

The way the truck crew organize their work depends on a number of factors,

including the power of their union, and may be partic- ularly difficult to modify The most common method, and in many respects the preferable one, is operation on the basis of a predetermined daily route plan A variation of this is operation

on the basis of a predefined weekly route plan, which offers Flexibility in the daily schedules Other methods include opera- tion on the basis of a predefined waste load that each truck has

to collect daily, or on the basis of fixed working-hours schedule

Rationalization of the actual route to be followed is often achieved in practice through simple heuristic approaches, without the use of computer models These procedures define sets of simple rules that have to be followed during route planning stages so as

to obtain near optimum solutions Table 10,3.2.2-1 lists the basic

rules for the heuristic method developed by Shuster and Schur

(1974), while the diagram of Figure 10.3.2.2-6 demonstrates a

Management of Solid Wastes 10-15

routing pattern derived through the application of this method for

Figure 10.3.2.2-6 Heuristic routing pattern for manual collection or mechanical collection with

double-side loader collector (Source: Shuster and Schur U.S EPA)

As urban centres grow in size and as the available landfills near them are progressively exhausted, wastes have to be conveyed further and further away, and at a certain point this becomes prohibitively

expensive, and in some cases impossible, using collection trucks, Larger

vehicles, tractor-trailers, semi-trailers, railroad cars or barges, can

accomplish this task far more economically, Figure 10.3.2.3-1

10-16 Approaches for Consideration in Formulating Environmental Controt Strategies

Table 10.3.2.2-1 Basic Rules for the Rationalization of the Collec-

tor Truck Routing (Source: K.A Shuster and D.A

Schur U.S EPA)

Routes should not overlap or be fragmented Each route should be compact, consisting of street segments clustered in the same geo- graphical area

Total collection plus hauling times should be reasonably constant for each route in the community (equalized workloads)

The collection route should be started as close to the garage or motor pool as possible, taking into account heavily travelled and one-way streets (see rules 4 & 5)

Heavily travelled streets should not be served during rush hours

In the case of one-way streets, it is best to start the route near the upper end of the street, working down it through a looping process

Services on dead-end streets can be considered as services on the

Street segment that they intersect, since they can only be col- lected by passing down that street segment To keep left turns at a

minimum, collect the dead-end streets when they are to the right of the truck They must be collected by walking down, backing down, or making a U-turn

When practical, service stops on steep hills should be made on both sides of the street while the vehicle is moving downhill for safety, ease, speed of collection, wear on vehicle, and conserva- tion of gas and oi]

Higher elevations should be at the start of the route

For collection from one side of the street at a time, it is gener- ally best to route with many clockwise turns around blocks@,

For collection from both sides of the street at the same time, it

is generally best to route with long, straight paths across the grid before looping clockwise

For certain block configurations within the route, specific routing patterns should be applied

3clockwise turns are preferred as easier, safer and less time consuming

In order to facilitate the above operation, the creation of one or more transfer stations is required in locations as close as possible to the weighted centre of the individual solid waste production areas to be served In this, the wastes are transferred, with or without prior com- pression, from the collector vehicles to the larger vehicles for the

long-haul Transfer stations can be classified into two broad types, de-

pending on whether they provide compression or not:

Figure 10:3.2.3-1 Transfer vehicle transporting three large solid waste containers

Transfer stations without compression are the simplest to construct and

their capacity has traditionally varied from very small up to medium size However, recent trends favour the use of this tech- nology even for larger transfer stations This is due to the sim-

plicity and low cost of the entire system, and also to the exist- ing limitations on the gross weight of vehicles (vehicles filled

with compressed wastes often exceed the allowable weight limits)

The way the waste is transferred characterises the type of sta- tion, affects its complexity and defines its capacity range:

Direct discharge of the wastes from the collector vehicle into

open transport containers offers the simplest construction and

allows the building of units with very small (up to 150 tons/day) capacities A conventional excavator-loader could be operated from the collecting truck discharge platform for

spreading and "compacting" the emptied wastes into the container vessel

Discharge of the wastes from the collector vehicles onto an en-

closed platform, from which they are loaded into the transport

containers by various types of auxiliary equipment, results in

a more expensive and complex construction, but can serve a

10-18 Approaches for Consideration in Formulating Environmental Control Strategies

large number of collector vehicles faster, allowing the

building of units with capacities of up to 1,200 tons/day

Transfer stations with compression are more expensive to build and run,

but they offer the potential for Tower transportation costs as the

transport vehicles can carry heavier loads (if permitted by the

applicable vehicle gross weight limits), as well as extended life for the landfills Again, these transfer stations can be classi-

fied into two broad types, depending on the degree of compression

Transfer stations without waste balling are the most common As

before, there are two ways the waste is transferred:

# In smaller capacity stations (300 to 500 tons/day) the wastes

are discharged directly into a hopper/compactor system and fed

into the transport container, Alternatively, the wastes are discharged directly into a hopper and into the front-end of an enclosed semi-trailer or trailer container equipped with a hydraulic pusher mechanism, Figure

10.3.2.3-2 The latter facilitates waste loading by periodically pushing the wastes towards the back-side of the container, providing at the same time a degree of compaction,

at the unloading, landfill site as well

In larger capacity stations (over 500 tons/day) the wastes are emptied into an enclosed platform and/or into storage pits for

temporary storage, and from there are transferred into the hop- per/compactor system and fed into the transport container

Figure 10.3.2,.3-3 illustrates the operation of a typical sta- tion of this type Figure 10.3.2.3-4 presents an aerial photo- graph of a large transfer station serving the Greater Athens

Area and having a nominal capacity of 1,200 tons per shift and

two storage pits Each pit has a storage capacity of 700 mổ, is able to serve ten collector vehicles simultaneously, and feeds into two parallel compactor systems

Transfer stations with waste balling provide a high degree of com-

pression with typical end-product densities of about 1,100 kg/m?

for a broad range of municipal solid waste compositions The com-

pressed and balled wastes are discharged ready for loading and transfer, and their reduced volume allows transport vehicles to

carry larger quantities and thereby to reduce transfer costs

However, limitations on the allowable gross weight of vehicles may restrict, or even eliminate, the above advantage At-the landfill site the balled wastes can be arranged in an orderly way in layers conserving space and prolonging significantly the landfill useful life The latter however has been contested by some experts who argue that, due to the decomposition of the materials and the weight of the upper layers, the uncompressed or normally com-

pressed wastes gradually collapse, undergoing thus a natural form

of compression with nearly comparable end results

Management of Solid Wastes 10-19

Figure 10.3.2.3-2 Transfer station with direct discharge of the collector-truck wastes into a hop-

per/semi-tratler container and compaction inside the latter

Figure 10.3.2.3-3 Operation diagram of transfer stations with compression and direct discharge of

wastes into temporary storage pits

10-20 Approaches for Consideration in Formulating Environmental Control Strategies

Figure 10.3.2.3-4 Aerial photograph of a large transfer station with compression and direct dis-

charge of wastes into temporary storage pits (Courtesy: Association of the Com- munities and Municipalities of the Attiki Region, Greece)

alternative waste transport schemes: (a) direct haul to landfill (with

the collector trucks); (b) use of a transfer station without waste compression; and, (c) use of a transfer station with waste compression

In each of these diagrams the requirements in vehicle trips, Jabour man-

hours and vehicle milage per 60 m3/d of wastes transported to a landfill

site 15 km away are listed The time required per each round trip has been assumed to be one hour

Despite the fact that the distance to the disposal site in our example

is reasonably short, the differences in the resource requirements among the three alternatives transportation systems appear rather striking

These differences are accentuated as the distance to the disposal site

grows On the other hand, transfer stations require relatively high

capital investment for their creation and labour for their operation and

these requirements are higher if waste compression is to be included

To decide whether transfer stations are economically justified, one can

assess and compare the sum of the operating and capital investment costs

for transportation through direct haul and through transfer stations

without waste compression If the comparison is in favour of the

transfer station solution, one has to perform similar cost analysis

between stations with and without waste compression to decide which type

of station is best The above screening work can be completed fairly

fast and with modest resources The way to proceed from this point

onwards depends on the size and the complexity of the problem:

Management of Solid Wastes 10-21

ane oon’

ee dì

(a) Direct Haul Requirements: 4 hauls/d, 16 man-hr/d, 120 km/d

1,200 hauls/y, 4,800 man-hr/y, 36,000 km/y

(b) Transfer station without compaction Requirements: ? Tong-hauTs/d, 2 man-hr/d, 80 km/d

600 lọng-hauls/y, 600 man-hr/y, 18,000 km/y

{c) Transfer station with compaction Requirements: 1 Tong-hau1 /d, 1 man-hr/d, 30 km/d

300 long-hauls/y, 300 man-hr/y, 9,000 km/y

Figure 10.3.2.3-5 Simplified diagram of vehicle and manpower requirements for alternative waste

transfer systems, Basis: waste quantity 60 mổ/d, Tandfi11 distance 15 km

10-22 Approaches for Consideration in Formulating Environmental Control Strategies

For large study areas and complex problems, further in-depth analysis is

required, which includes the search for alternative transfer sta-

tion sites, calculates the optimum number of transfer stations, finds the most suitable type and the optimum capacity of each sta- tion, and defines the areas served by each of them Additional

work is often required, such as sensitivity analyses for alterna- tive solutions which might be more appealing to citizens and to political decision makers The above procedure is often part of more integrated planning, which includes alternative waste

processing and final disposal options, and is carried out with the use of appropriate computer models

It is interesting to note in this regard that the computed optimum

number of stations balances the economies of scale resulting from the construction of fewer larger stations against the economies in transportation from the easier accessibility offered by a greater number of smaller stations

In the case of small to medium size communities the analysis require-

ments are far simpler than those described above and the system can often be adequately optimized through common sense and engi- neering judgement, without sophisticated computer analysis

As a simple rule of thumb, the creation of transfer stations is economically justified when the distance to the disposal site is over 15 km In many cases transfer stations, with direct discharge

of the collector truck wastes into the transportation containers,

such as that illustrated in Figure 10.3.2.3-2, or even simpler with open containers and without waste compression, offer low-cost and simple to operate solutions

stations, marked with smaller circles between the community

clusters Each transfer station has a simple construction

comprising a ramp allowing direct discharge of the collector truck wastes into an open container The containers are periodically

picked up by a single tractor, which starts with an empty con- tainer, visits the first transfer station leaving the empty con-

tainer and picking up the filled one, carries the container to the

Tandfill area where it unloads its contents, and carries on in the same manner visiting the second and the remaining transfer sta- tions The daily course of the tractor is illustrated in Figure 10,3.2.3-5 by the arrow-lines

Management of Solid Wastes 10-23

Figure 10,3,.2.3-5 Simplified diagram of a transfer station network serving numerous small communt-

ties in a region, sharing a single sanitary landfill and transportation tractor

10.3.2.4 Processing

As Figure 10.3.2-1 shows, municipal wastes can be processed prior to their ultimate disposal The objective of waste processing is to reduce

their volume and quantity and/or to recover useful materials and energy

After-collection processing should not be considered as an alternative

to separation at the source, even if it includes recovery, since the yield and purity of the materials recovered is much reduced and the processing costs are high

Sound environmental practice supports waste processing, as it reduces the quantities of wastes to be disposed of, conserves precious natural resources, and lowers energy and water consumption and air and water

pollution through manufacturing processes (see for example Table

10.3.2.1-1) From the economic point of view however, waste processing

is rarely profitable, as the value of the resources recovered represents, in general, only a fraction of the processing cost Direct waste landfilling remains the most economical option

Opinion is slowly shifting in favour of waste processing Indeed, as the

potential landfill sites, which are close te large urban centres, are becoming exhausted, the unprocessed disposal of wastes accentuates the

difficulties of finding new disposal sites and results in ever

increasing transportation costs On the other hand, improving standards

10-24 Approaches for Consideration in Formulating Environmental Control Strategies

of living and the changing composition of collected wastes tend to

enlarge the fraction of recoverable resources in wastes, and thus to take processing operations economically more attractive As a result of these trends, waste transport is becoming better

organized, mainly through the construction and Operation of transfer stations, while

compression, a form of solid waste processing, is increasingly carried out at all waste handling stages (in compacting collector trucks, in

transfer stations, and in landfill operations) Manual and/or mechanical separation, incineration, or composting represents the next step in this waste processing direction

Figure 10.3.2.4-1 Process diagram and material balance of a 20 tod pilot wastes separation and

compasting plant operating in the Greater Athens Area (Source: P Economopaylos,

È Capetanios and C Ziogas Association of Communittes and Hunielpalitiles of

Attika Region)

Manual and/or mechanical separation yields a number of recycled prod-

ucts, with RDF (refuse derived fuel) and ferrous metals, but also

paper and glass, being the prime candidates In a typical instal- lation such as this illustrated in Figure 10.3.2.4-1, plastic bags are mechanically torn apart, bulky cardboards, and large metal and textile pieces are picked up by hand as the waste passes along a conveyor belt and recovered, mainly for protecting the mechanical

equipment that follows The remaining wastes are mechanically

separation, and mechanical systems, such as vibrating screens, ballistic separators or air Separators, are used for separating

the remaining waste into enriched organic fractions suitable for

composting (free from metals, glass and plastic), RDF,

and

leftover inert materials for disposal

Management of Solid Wastes 10-25

Composting may follow the separation, as Figure 10.3.2.4-1 illustrates

This is an aerobic stabilization process that converts properly

separated and enriched organic fractions of solid wastes into a humus like material, The raw compost is refined by mechanical

separators so as to remove inert and other waste materials and yield a high quality compost product that can be used as a soil conditioner to improve soil structure and to increase its moisture

and nutrient holding capacities As composting is a natural biological process, ong residence times are required for

stabilization and maturation reactions to complete As a result, the process area requirements are rather large ranging from 100 to

150 m? per ton of raw wastes per day Close quality control and existence of a compost market in the vicinity of the plant are prerequisites for the proper operation and economic justification

of composting facilities Heavy metal concentrations must be carefully checked as their presence in other than trace amounts

renders the compost unsuitable as a product, or places strict limitations on its use Figure 10.3.2.4-1 presents the material balance from the final test operation of a 20 tpd capacity plant

operating in the Athens area

Incineration offers significant reductions in waste weight, Table 5.2.2-

2, and especially in waste volume, and, depending on waste composition, it may also provide the opportunity for recovery of energy However, the investment costs are high, especially if air pollution controls are practiced, as ought to be, while the

operating costs can ‘be prohibitively high, if wastes with a low calorific value (LCV), below 2,700 kcal/kg, are involved (external

fuel must be consumed to sustain the combustion) Wastes with LCVs between 2,700 and 3,300 kcal/kg allow self-sustained combustion through waste preheating, and only those with LCVs above 3,300 kcal/kg allow net energy gains It should be noted in this regard

that the high putrescible content of wastes from most, developing countries makes them unsuitable or of marginal quality for direct combustion However, pre-processing could separate the incoming

wastes into putrescible rich and putrescible poor fractions and the latter can be incinerated

Processing plants with simple and reliable systems and easy operation have been reported to provide a more lasting and successful operation in developing countries than complex and sophisticated ones

10.3.2.5 Disposal

A major parameter that defines the suitability of a potential landfill

site is its capacity, as it should provide a useful life span of at

Jeast 5 to 10 years The required landfill volume can be computed from the following Equation:

10-26 Approaches for Consideration in Formulating Environmental Control Strategies

R, (10.3.2.5-1)

where,

Population served

Weight of solid wastes collected, kg/capita/yr (see

Solid Wastes Inventory Model of Section 5.2.2)

Density of compacted fill, kg/mg (can be estimated

from Tables 5.2.2-2 and 5.2.2-3 as function of the known composition)

R = Volume-ratio of cover soil to compacted fi1] (typical

values from 1.25 to 1.35)

=v ou

=> li W

Once the minimum size requirements for the landfill have been estab-

lished, the search for candidate landfill] areas can begin For this pur- pose aerial photographs, topographic or contour Maps, geotechnical and

hydrogeological maps are normally used for the initial screening More

detailed site-investigations follow, and the eventual selection of the landfill sites to be used is based on criteria such as:

# The likely intensity of public opposition This often emerges as a dominant factor that affects the final choice

# Adherence to zoning requirements (e.g in the USA, the minimum dis-

tance requirements are 65 m from houses, schools and parks, 30 m from streams, 160 m from drinking water wells; in Greece, the mini-

mum distance from houses is 500 m);

® pact on transfer costs; Proximity to the urban area served, as it has a rather obvious im-

# Road accessibility (proximity to roadways, traffic congestion, vehi- cle gross weight limitations, bridge capacities and underpass Jim- its);

® Area hydrology (ground permeability and depth of aquifer) The pres - ence of natural low permeability clays, schists, silts, or silty

sand with high clay content, is advantageous as it may eliminate the

need for expensive lining (see below), while an aquifer depth, well below the bottom of the Tandfill, is normally required;

® Climatic conditions (wind direction and wind velocities, lack of floods, mud slides, snow etc);

% Availability of cover material

If the hydrological conditions are not satisfactory, the selected land-

fill has to be lined so as to prevent the pollution of underground water

and/or of nearby surface waters For this Purpose various lining tech-

niques and materials have been used, including the application of com-

pacted clay, asphalt, synthetic chemicals (polymers, rubber latex), and

synthetic membrane Tiners (U.S EPA, 1988 and 1989) In addition, the landfill has to be equipped with underdrain pipes for the control of

Management of Solid Wastes 10-27

Teachates The collected Tleachates are fairly strong effluents (see Table 4.2.2-5) and could be piped to the nearest sewer receiver, can be

treated locally and discharged into a wastewater receiver, or can be

collected and recycled back into the landfill In the latter case the

effluent eventually evaporates, provided that the climate is not very wet, due to the exothermic reactions taking place inside the landfill

At the same time, a higher methane gas yield has been observed, as the increased humidity of the wastes tends to favour the anaerobic decomposition of organics To minimize the volume of the leachates generated, and to facilitate the daily operations, the runoff waters should be diverged through canals and not allowed to enter the landfill

Under normal landfill operation the wastes are spread each working day over a fill area and compacted by bulldozers or compactor vehicles By the end of the day the piled wastes, with a thickness of between 2 to 3

m, are covered by about 0.25 m of material, preferably low-clay soil In

some modern Jandfill operations, with waste shredded and well compacted,

the daily cover is omitted Daily fills are placed adjacent to each

other until a layer covering the entire working landfill area has been completed Successive layers are normally placed on top of one another

until the maximum height is reached At that point a final layer of cover material is placed on top with a thickness of at least 0.6 m

Depending on the source of cover material, the landfill operation meth-

ods are distinguished into area and trench In the former method the

cover material must be available from elsewhere (e.g demolition debris

hauled by trucks) In the latter method a trench is excavated first and

the removed soil is used subsequently as cover material A mixed operat- ing mode is also possible and often practiced,

The anaerobic decomposition of the organic material yields biogas that

contains a significant fraction of methane and can be used directly as fuel in nearby industries, such as lime or cement kilns and asphalt concrete plants, or, after processing for purification and enrichment,

it can be fed into the city gas distribution network or it can be used locally for the generation of electricity Biogas recovery is not widely practiced, but appears to be economically justified for large landfill sites To achieve maximum gas recovery, the landfill operation needs to

be organized on a so called "caroussel" mode According to this, the dumping of wastes is restricted during a certain period (e.g one year)

in a predefined area At the end of this period the stacked wastes have reached the maximum level, and the dumping operation is shifted to an adjacent area Over the filled area, gas lines are connected to a grid

of gas wells and the produced gas is collected and commissioned for ex-

10-28 Approaches for Consideration in Formulating Environmental Control Strategies

In most study areas the number of cars to be disposed of grows rapidly,

fotlowing closely, through a constant time lag, the ever expanding size

of the car fleets Junk cars contain metals and plastics that can be recycled, and there is often a sufficient private and/or public incen- tive in this direction, as the recycling operation is generally prof- itable If the number of recycled cars is large enough, heavy shredders can be used to process them in a feed form suitable for steel mills

However, as the cost of the shredders is high, simpler equipment is of- ten used for the same purpose

Recycled cars contain lub oils, greases, fuels, as well as batteries with acidic solutions and heavy metals (Pb) If these materials are not removed prior to the car shredding and processing, serious ground pollu- tion will occur

10.3.4 Sludges from Municipal Wastewater Treatment Plants

The disposal of municipal sludge is a major concern for planners and

operators of wastewater treatment works, as the quantities to be disposed are a relatively sizeable portion of the treated wastewater (see the solid waste inventory model of Section 5.2.2)

As discussed below, a fair number of alternative sludge disposal methods

exist, provided that the sludge is free from heavy metals and other

toxic materials, Wastewater treatment plants serving domestic sources

yield sludges free from toxic problems This however may not be the case

for sewerage systems receiving industrial effluents, or for urban sewer systems in which industries are connected In such cases the sludge dis- posal options are severely restricted and the disposal costs signifi- cantly increased In cases where the sludge contains appreciable amounts

of toxic substances, the most economically effective and environmentally responsible management approach is to deal with the individual toxic sources by controlling their wastes prior to their discharge into the sewer system (for the development of relevant strategies see Section 9.1.4.5) For the remainder of this section the assumption will be made that the sludges to be disposed of are free from toxic substances, other than in trace amounts

Alternative sludge disposal methods include the incineration (separately

or along with municipal solid wastes), barging and ocean dumping, utilization in the manufacture of marketable products, disposal into municipal landfill sites mixed with municipal solid wastes, and disposal

on land other than in landfills:

Incineration is expensive and, assuming that air pollution controls are

applied, the solid wastes problem is reduced but not eliminated

Nonetheless, the waste residues can be disposed of safely to

sludge-only disposal sites, as well as co-disposed with domestic wastes in normal landfill sites, Table 10.3.4-1

A

Manageiment of Solid Wastes 10-29

Ocean dumping is considered poor practice from the environmental stand-

point and tends to be abandoned Its use is limited by several In- ternational Conventions and is prohibited by the United States

Sludge utilization includes composting along with municipal or green-

yard refuse, bioconversion to ethanol, production of activated

carbon, etc These possibilities are finding increasing favour and

can absorb some quantities, but at present they do not constitute

a general solution to the sludge disposal problem

Landfilting of sludges is widely practiced as it offers a practical

solution for many wastewater treatment plants, especially the large ones serving populated urban centres Sludge landfill

methods can be grouped into three general categories: sludge-only

trench fill, sludge only area fill, and co-disposal with refuse

In the Sludge-anly Trench Fill method, trenches are excavated and dewatered sludge, or in some cases liquid stabilized and unstabi-

lized sludge, is buried entirely below the ground surface The sludge is deposited directly into the trench from a haul vessel and covered daily by a layer of cover material An idea of the

landfill area requirements can be obtained by considering that in

narrow-trench application (trench widths < 3 m, suitable for solid sludge contents as low as 3 %), the application rates range from

230 to 1100 m? of sludge per 1000 m? of land, while in wide trench

application the application rates range from 600 to 2700 m of sludge per 1000 m@ of land

In the Sludge-only Area Fill method, the sludge is mixed with soil and the mixture is placed on the ground surface Substantial quan-

tities of imported soil may thus be required, but the method is

suitable in areas where ground water is shallow or the bed-rock

prevents excavation Daily cover is not usually provided, and for

this reason stabilized sludge is best suited for this method

Landfill Vining and adequate drainage and runoff controls may be required to prevent groundwater and nearby surface water contami-

nation

In the Co-disposal with Refuse method the sludge is disposed of at

a refuse landfill mixed either with refuse or with soil In the Sludge/Refuse mixture operation, stabilized or unstabilized sludge, with a solids content of 3 % or greater, is thoroughly

mixed with refuse in proportions 1 to 10 Following this, the mixture is applied on top of the working face of the landfill,

compacted, and covered with soil according to normal operating practices for municipal waste landfills, Section 10.3.2.5 In the

Sludge/Soil mixture operation, the sludge is mixed with soil and

the mixture is used as cover material for the daily fills This method requires stabilized sludge with at least 20 % solids content and the application rate ranges from 95 to 790 m of

sludge per 1000 m? of Tandfill area

10-30 Approaches for Consideration in Formulating Environmental Control Stratagies

Table 10.3.4-1 Suitability of Sludges for Landfilling (Source: Munici-

pal Environmental Research Laboratory, Process Design manual for sludge Treatment and Disposal U.S EPA)

and WAS, WAS without chemicals NS

Flotation thickened WAS with chemicals NS

Thermal conditioned primary or WAS NS

Liquid - Stabilized

Thickened anaerobic digested

primary and primary, and WAS

Thickened aerobic digested primary and primary, and WAS Thickened lime stabilized

primary and Primary, and WAS

Dewatered - Unstabi lized

Vacuum filtered, lime

conditioned primary

Dewatered - Stabilized

Drying bed digested and lime stabilized Vacuum filtered, lime conditioned digested Pressure filtered, lime conditioned, digested Centrifuged, digested and Time conditioned digested Heat Dried

Heat dried digested High Temperature Processed Incinerated dewatered

primary and primary, and WAS

Wet-air oxidized primary, and primary, and WAS

Waste Activated Sludge Not Suitable

Marginally Suitable Suitable

Odor problems Operational Problems

Management of Solid Wastes 10-31

Table 10.3.4-1 provides guidance about the suitability of sludges generated from various treatment processes in relation to the

landfilling operations described above In general, only stabi- lized and dewatered sludges are recommended for landfill disposal

For sludge-only landfills, the solids content should be greater or equal to 15 %, but soil can be used as a bulking agent to effectively increase the solids to that level, For co-disposal

solids concentrations down to 3 % can be tolerated,

The disposal on land, other than in landfills, can provide a cost effec-

tive and environmentally safe sludge management option This is

particularly suited for treatment plants serving small] to medium size urban areas as the sludge quantities are not so large, are

generally free from heavy metals, and cultivated and/or forest lands are available at close distances It is estimated that as much as 40 % of the total quantity of municipal sludges produced

in the United States is disposed of by this method, EPA (1983)

The Agricultural Utilization of the sludge is practiced in many

areas and for many centuries and provides the participating farmers with a substitute or supplement for conventional

fertilizers The sludge is applied in "agronomic rates" (in accordance with the annual phosphorus and nitrogen requirements of

the crops) and benefits plants by offering a number of

micronutrients, such as B, Mn, Cu, Mo, and Zn Sludge, added at higher than agronomic rates, becomes a valuable soil conditioner making soil looser and more friable, while increasing the amount

of pore spaces and the water holding capacity If toxic substances are present, the quantity of sludge applied must be subject to

strict limitations in relation to the annual quantity per acre

used, and observed on a cumulative basis as well This practice may be limited in some areas by the reluctance of farmers to accept sludge in their fields

Application to Forest Land is suitable for municipalities located

in proximity to forests as it offers P and N and essential mi- cronutrients, often Tacking in forest soils In addition there are

fewer public health concerns related to the fate of toxics in cases where there is a limited presence of toxic substances in the sludge On the negative side, access to some forest lands may be

difficult for conventional sludge application equipment, while some public health concerns may arise from the normally unre-

stricted access of the public to sludge-amended forest lands

Application to Reclamation or Disturbed and Marginal Lands such as from surface coal mining or from mine tailing operations, is highly beneficial as such soils Jack N, P, micronutrients and organic matter, and have poor physical, chemical and biological properties This way, the existence of marqinal lands in the vicinity of the treatment plant offers the opportunity not only to dispose of the generated sludges, but also to reclaim land, and highly successful applications have been reported

Dedicated Land Disposal offers the possibility of applying sludge

at a high annual rate for many years over a limited area, and this

10-32 Approaches for Consideration in Formulating Environmental Control Strategies

reduces sludge distribution requirements and the transportation costs Moreover, sludges with a limited content of toxic sub- stances, may be acceptable using the present method On the negative site, the site may become the source of bad odours and other nuisances, while the control of surface water runoffs and leachates may be expensive Moreover, the disposal area may become unsuitable for future use in agricultural production or forestry due to the accumulation of toxic substances,

Hospital wastes can be classified according to EC in the categories of Similar-to-domestic, infectious, and special wastes:

The similar to domestic waste category comprise kitchen refuse, wrapping

and other wastes, which do not present any particular health haz- ard in their handling and disposal These can be disposed of along with municipal solid wastes

The infectious waste category comprises tissues, organs, body parts and

fluids, cultures of contagious viruses, excreta from patients with highly contagious diseases, etc It comprises also, sculpts, nee-

dies, bandages, and other wastes from surgical and laboratory op- erations WHO recommends that these wastes should be collected in specially marked sturdy bags and incinerated in appropriate in-

stallations The photograph of Figure 10.4-1 demonstrates such an

incinerator system for hospital wastes

As the cost of incinerator equipment is high, on site incineration tends to be economically justified only for large hospitals This often necessitates the organization of a separate collection system feeding a central incineration installation, which serves all hospital and smaller clinics without relevant on-site facili- ties,

Special waste category comprises radioactive materials, spent chemicals

from diagnostic or experimental operations, pharmaceutical

preparations and drugs expired or leftover after use, etc Depend- ing on the nature of these wastes, recycling, incineration or other processing and disposal methods need to be used

The solid wastes inventory model of Section 5.2.2 can be used to make a preliminary assessment of the quantities of infectious and special wastes generated

Figure 10.4-1 Photograph of a twin incinerator system for infectious and special wastes

10.5 Management of Industrial Hazardous Wastes

The basic steps normally involved in the generation and management of

hazardous wastes are illustrated in Figure 10.5-1 and a brief description of them is given below:

1 Waste Generation is affected by the methods used at the source, and

creates the need for in-house storage

Waste reduction can be achieved, often with economic profit in

jarger installations, through a variety of methods, the choice and combination of which depends, not only on the type of installation, but also on the particular source as well These methods include the following:

(a) Modification of processes and operating practices For exam-

ple, in electroplating operations multi-step counter-current

washing of the plated products substantially reduces the heavy

metal and other toxic pollutant discharges;

(b) Changes in the raw materials For example, in electroplating

operations by changing the cyanide plating baths to acid baths

we eliminate toxic cyanide discharges;

10-34 Approaches for Consideration in Formulating Environmental Control Strategies

Reduction Storage

Figure 10,5-1 asic Steps in Hazardous Waste Management

(c) In-House Recycling and Reuse For example, in electroplating

operations the recovery of heavy metals from electroplating wastewaters and spent bath solutions, or in chrome tannery op- erations the recovery of chromium from the effluent sludges, eliminates to a large extent the heavy metal discharges Waste exchange between neighbouring industries may also be a very

effective way to reduce the quantities of certain wastes for example, phosphoric fertilizer plants utilise sulfur for pro- ducing sulfuric acid, while they generate gypsum from their

process and hydro fluosilicic acid from their air pollution

control systems Their sulfur needs can be satisfied by petroleum refineries (sulfur is a by-product of the sulfur re- covery units), the generated gypsum can the used by gypsum

Management of Solid Wastes 10-35

board manufacturing plants and the generated hydro fluosilicic acid by primary aluminum production plants

In-House Processing For example, in oil refineries or in

petrochemical plants, large quantities of oily wastes produced can be incinerated and/or landfarmed internally so as to

eliminate the oily wastes problem Neighbouring plants may co- operate sharing the use of their waste processing facilities

The latter is often particularly effective from the economic stand-point as the capital and operating costs for hazardous wastes processing equipment tends to be high

In-house storage of the produced wastes makes possible the ratio- nalization of the waste collection scheme, even when the hazardous waste quantities are small, as they can be accumulated for a period

of time rendering their periodic collection practical and economic

The practicality aspect is a particularly important one, especially

in the early stages of a hazardous waste management programme, for unless there is convenient storage of adequate capacity and reliable periodic pick-up, process operators tend to avoid the hassle and the

delays of dealing properly with their toxic wastes and end up disposing of them in an improper manner (e.g by dumping in the

sewage system) as practiced in the past

Waste Collection involves the periodic pick-up of hazardous wastes from the various sources and their transportation to either a final

disposal site, to an interim storage site, or to a hazardous waste processing site The proper organization of the collection system

regulatory authority and defines, to a very large extent, the suc- cess of the entire hazardous waste management effort

Organization of the collection system on a private basis by the waste producer, is certainly a rational arrangement when large quan-

tities of wastes are generated, as for example by large industries such as refineries, fertilizer or metallurgical plants

Organization of a collection system by the pollution control author- ity, can be planned to serve numerous smaller toxic waste producers, and may offer important practical advantages, especially in the early management stages Indeed, a system of this type provides the opportunity for regular direct inspection of the interim storage fa-

cilities, allows the monitoring of waste generation quantities and

statistical analysis on the basis of historical data from the same and similar sources, and establishes a closer contact with the producer making it easier to exchange experiences on waste recycling

and reuse possibilities Moreover, if at early programme stages this service is offered free of charge (recommended for selected small

sources with particularly troublesome wastes, such as electroplating

or battery manufacturing plants) the possibilities of successful

implementation are further enhanced

Interim Storage of collected wastes is not always required, especially in cases where the processing and/or the final disposal Sites are close to the sources The purpose of the interim storage