solid waste and solid waste management

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Solid Waste and Solid Waste Management Municipal solid waste ( MSW ), commonly known as trash or garbage in the U.S. and as refuse or rubbish in the UK , is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste , as in a garbage disposal ; the two are sometimes collected separately. The municipal solid waste industry has four components: recycling , composting , landfilling , and waste-to- energy via incineration. [5] The primary steps are generation, collection, sorting and separation, transfer, and disposal. Activities in which materials are identified as no longer being of value and are either thrown out or gathered together for disposal. Solid waste means any garbage, refuse, sludge from a wastewater treatment plant, water supply treatment plant, or air pollution control facility and other discarded materials including solid, liquid, semi-solid, or contained gaseous material, resulting from industrial, commercial, mining and agricultural operations, and

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This would help you to have a few knowledge about the solid waste and solid waste management.What is Municipal Solid Waste and how this solid waste is treated.

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Page 1: Solid Waste and Solid Waste Management

Solid Waste and Solid Waste Management

Municipal solid waste (MSW), commonly known as trash or garbage in the U.S. and

as refuse or rubbish in the UK, is a waste type consisting of everyday items that are discarded

by the public. "Garbage" can also refer specifically to food waste, as in agarbage disposal; the

two are sometimes collected separately.

The municipal solid waste industry has four components: recycling, composting, landfilling,

and waste-to-energy via incineration.[5]The primary steps are generation, collection, sorting and

separation, transfer, and disposal. Activities in which materials are identified as no longer being

of value and are either thrown out or gathered together for disposal.

Solid waste means any garbage, refuse, sludge from a wastewater treatment plant, water supply

treatment plant, or air pollution control facility and other discarded materials 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

Examples of solid wastes include the following materials when discarded:

waste tires

septage

scrap metal

latex paints

furniture and toys

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garbage

appliances and vehicles

oil and anti-freeze

empty aerosol cans, paint cans and compressed gas cylinders

construction and demolition debris, asbestos

A material is discarded if it is abandoned by being:

disposed of;

burned or incinerated, including being burned as a fuel for the purpose of recovering usable

energy; or

accumulated, stored or physically, chemically or biologically treated (other than burned or

incinerated) instead of or before being disposed of.

Collection of Refuse

Waste collection is a part of the process of waste management. It is the transfer of solid

waste from the point of use and disposal to the point of treatment or landfill. Solid waste from

households and commercial establishments is collected by trucks. Vehicles that collects solid

waste are called packers. Trucks that use hydraulics rams to compact the refuse to reduce its

volume and make it possible for the truck to carry larger loads. Commercial industrial collections

are facilitated by the use of containers that either emptied into the truck by using hydraulic

mechanism or carried to the disposal site.

Household collection of mixed refuse is usually by a packer truck with one or two

workers; one driver and one loader. These workers dump the refuse for the garbage cans into the

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truck then drive the full truck to the disposal area. The entire program is a study of in

inefficiency and hazardous work.

Various modification to this collection method have been implemented to cut collection

cost and reduce accidents, including the use of compactors and garbage grinders in the kitchen

and semi-automated and full automated collection. Other alternate systems have been developed

for collecting refuse, one especially interesting one being a system of underground pneumatic

pipes. The pneumatic collection system at Disney World Florida has collection stations scattered

throughout the park that receives the refuse, and the pneumatic pipes deliver the waste to a

central processing plan.

The selection of a proper route for collection vehicles, known as route optimization can

result in a significant savings to the hauler. Leonard Euler was asked to design a parade route for

Koninsgsberg such as that parade would not cross any bridge over the River Pregel more than

once and would return to its starting place.

Not only did Euler show that such a route was impossible for the king’s parade but he

generalized the problem by specifying what conditions are necessary to establish such a route,

now known as a Euler’s tour. Travel takes place along links that connect nodes.

Generation of Refuse

The science of ecology teaches us if dynamic ecosystems are to remain healthy, they

must reuse and recycle materials. In simple ecosystems. Such as ponds and lakes, for example,

phosphorus is used during photosynthesis by the aquatic plants to build high energy molecule,

which are then used by aquatic animals, and when both produce waste and die, phosphorus is

released so it can be reused.

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The flow of materials through the human ecosystem is like the flow of nutrients or energy

through natural ecosystems and can be similarly analysed. Black Box represents Human Society

just as we use a Black Box to represent an ecosystem. In an ecosystem, nutrients are extracted

from the earth used by living organisms and then redeposit on earth. Similarly, human society

uses raw materials extracted from the earth that are manufactured into products to be used by

human beings and then discarded.

If a raw Material, such as iron is considered a steady state, the amount of iron ore

extracted from earth muse equal the amount of iron discarded as ferrous materials (IN=OUT).

[Rate of Materials Accumulated] = [Rate of Materials IN] – [Rate of Materials OUT] + [Rate of

Materials PRODUCED] – [Rate of materials CONSUMED]

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Fig 14.11 is more detailed representation of materials flow through human society. The

width of the bands is intended to indicate the mass rate flow. The wider the band, the larger the

flow. All materials originate from earth, and the amount of material extracted is represented in

the figure by the letter “A”. These raw materials such as iron ore and oil that feed industry. These

materials are extracted and fed into the manufacturing sector for the production of useful goods.

Not all the extracted materials can be used, however, and some become industrial waste

that must be disposed in the environment. In addition, some materials become industrial scrap

and can be used by the same industry or shipped to some other industry through waste exchange.

The primary distinction between scrap and other types of secondary materials is that scrap never

enters the public sector.

Reuse and Recycle of Materials from Refuse

The public can exercise three alternate means for getting rid of its unwanted material

once it is generated – reuse, recycling and disposal. In reuse an individual either uses products

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again for the same purpose or puts products to secondary, often imaginative, use. An example of

the former is buying milk in glass containers and returning the containers to the store for the milk

distributor to clean them and put fresh product into them.

Recycling or material recovery, on the other hand, involves the collection of waste and

subsequent processing of that waste into new products. For example turning plastic food

containers into park benches or clothing or used aluminium cans back into aluminium cans.

Manufacturers can enhance the feasibility of recycling and recovery of materials by consciously

producing products that are simple and inexpensive to recover or recycle or that can be reused.

A central processing facility is known as a material recover facility or MRF. The main

feature of material recovery in a MRF is that the recovered materials are produced from mixed or

source separated domestic waste and are then reintroduced into industrial use. Note that the

recycling process must include collection processing, transport and sale of the material.

Processing of the Refuse

In both methods, reuse and recycling, the primary goal is purity. For example, the daily

refuse from a city of 100,000 would contain perhaps 200 tonnes per day of paper. Secondary

paper has sold about $20/tonne so income community would be $4000 per day. Source

Separation in which the public separate their waste into different types. But this recycling

program rely on voluntary cooperation.

Another way is letting the MRF handle all the separation of waste. This will reduce the

public’s role and reduces collection cost. But increases the complexity of and the processing cost

at the MRF. Theoretically, however vast amounts of materials can be reclaimed from refuse, but

this is not an easy task regardless of how it is approached.

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In recycling, the code is unusually simple and visual. Anyone can identify newspaper

from aluminium cans. But sometimes confusion can occur, such as identifying aluminium cans

from steel or newsprint from glossy inserts.

The most difficult operation in recycling is the identification and separation of plastic

because mixed plastic has few economical uses, plastic recycling is economical only if the

different types of plastic are separated from each other. However most people cannot distinguish

one type of plastic from another. The plastic industry has responded by marking most consumer

products with a code that identifies the type of plastic.

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Mechanical recovery operations have a chance of succeeding if the material presented for

separation is clearly identified by a code and if the switch is then sensitive to that code. Currently

no such technology exist. In fact the most recovery operations are employ pickers human beings

who identify the most readily separable materials.

Markets for Processed Refuse

The recovery of materials is still a marginal option. The most difficult problem faced by

engineers designing such facilities is the availability of frim markets for the recovered product.

Occasionally, the markets are quite volatile and secondary material prices can fluctuate wildly.

One example is the secondary paper market.

Paper industry is what is known as vertically integrated, meaning that the company owns

and operates all the steps in papermaking process. The own lands on which the forest are grown;

they do their own logging and take the logs to their own papermill. Finally, the company markets

the finished paper to the public.

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Suppose a paper company has base demand of 100 million tonnes of paper. It then adjust

the logging and pulp and paper operation to meet its demands. Now suppose there is a short term

fluctuation of 5 million tonnes that has to be met. There is no way the paper company can plant

trees necessary to meet this immediate demand nor able to increase the capacity of the pulp and

paper mills in such short notice. What they do then is to go to a secondary paper market and

perchance fiber to meet the incremental demand.

Combustion of Refuse

One product that always has a market is energy. Because refuse is about 80%

combustible material, it can be burned as is, or it can be processed to produce a refuse-derived

fuel (RDF). The cross section of typical waste-to-energy (WTE) facility is shown.

The refuse is dumped from the collection of trucks into pit to mix and equalize the flow

over the 24 hour period since such facilities must operate around the clock. A crane lift the refuse

from the pit and places it in a chute that feeds the furnace. The grate mechanism moves the

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refuse, tumbling it and forcing in air from the bottom and the top as the combustion takes place.

The hot gases produced from the burning refuse are cool with a bank of tubes filled with water.

As the gases are cooled, the water is heated producing low power steam, the steam can be used

for heating and cooling or for producing electricity in a turbine. The cooled gases are then

cleaned by pollution control devices. Such as electrostatic precipitators and discharged through a

stack.

Because solid waste can be combusted as is and because it can also be processed in many

ways before combustion, there might be confusion as to what exactly is being burned. The

American Society for Testing and Materials (ASTM) developed a scheme for classifying solid

waste destined for combustion:

RDF-1 Unprocessed MSW

RDF-2 Shredded MSW (but no separation of materials)

RDF-3 Organic Fraction of Shredded MSW

RDF-4 Organic Waste produced by a MRF that has been further shredded into

fine, almost powder, form, sometimes called “fluff”

RDF-5 Organic Waste produced by a MRF that has been densified by a pelletizer

or a similar device and that can often be fired with coal in existing

furnaces.

RDF-6 Organic Fraction if the waste that has been further processed into a liquid

fuel, such as oil.

RDF-7 Organic Waste processed into gaseous fuel.

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Ultimate Disposal of Refuse: Sanitary Landfills

The disposal of solid waste is a misnomer. Our present practices amount to nothing more

than hiding the waste well enough so it cannot be readily found. The only two realistic options

for disposal are in the oceans and on lands.

Although the volume of the refuse is reduced by over 90% in WTE Facilities the

remaining 10% still has to be disposed of somehow, along the materials that cannot be

incinerated. A landfill is therefore necessary even if the refuse is combusted and a WTE plant is,

therefore, not an ultimate disposal facility. The placement of solid waste is called dump in the

United States and tip in Great Britain.

Rodents, odor, air pollution and insects at the dump, however can result in serious public

health and aesthetic problems, and alternate method for disposal are necessary. While larger

communities can afford an incinerator for volume reduction, small communities cannot afford

such investment, so this led to the development of sanitary landfill.

The sanitary land fill differs markedly from open dumps in the latter are simple placed to

dump waste while sanitary landfills are engineered, operations, designed and operated according

to accepted standards. The basic principle of a landfill operation is to prepare a site with liners to

deter pollution of groundwater, deposit the refuse in the pit, compact it with specially built heavy

machinery with huge steel wheels and cover the material at the conclusion of each day’s

operation. Siting and developing a proper landfill requires planning and engineering design

skills.

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However sanitary landfills are not inert, the buried organic material decomposes, first

aerobically and then anaerobically, the anaerobic degradation produces various gases, such as

methane and carbon dioxide, and liquids known as leachate that have extremely high pollution

capacity when they enter ground water. Liners are made of either impervious clay or synthetic

materials such as plastic are used to try to prevent the movement of leachate into ground water.

Reducing the Generation of Refuse: Source Reduction

There is a third way we can affect the quantity and content of the solid waste stream:

carefully select the materials and products we use and hence, have to throw away. Consider the

utility of a person rejecting an unnecessary bag at a store the effort may be significant band the

convenience is less because not the purchase is not carried conveniently.

The question is why you to do something ought not measurable to your benefit? The

answer might be “it is the right thing to do”. This makes you feel like part of a community all

pulling together to achieve some good end. With every individuals actions totalling to a

significant effect.

One means of getting a handle on questions of material and product use is to conduct

what is known as life cycle analysis (LCA). Such analysis is a holistic approach to pollution

prevention by analysing the entire life cycle of a product, process or activity, encompassing raw

materials, manufacturing , transportation, distribution, use, maintenance recycling and final

disposal. In other words, LCA should yield a complete picture of the environmental impact and

product.

LCA’s are performed for several reasons, including the comparison of products

purchasing and the comparison of products by industry. In the former case the total

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environmental effect of, say glass returnable bottles could be compared to the environmental

effect of no recyclable plastic bottles.

LCA’s also suffers from dearth data. Some of the information critical to the calculations

is virtually impossible to obtain. For example something as simple as the tonnage of solid waste

collected is not readily calculably or measurable. And even if the data were there, the procedures

suffers from the unavailability of a single accounting system.

Integrated Solid Waste

The EPA developed a national strategy for the management of solid waste called

“integrated solid waste management” (ISWM). The intent of this plan is to assist local

communities in their decision making by encouraging strategies that are the most

environmentally acceptable but providing flexibility to manage waste efficiently. The strategies

being:

o Source Reduction

o Recycling

o Combusting

o Landfilling

That is when an ISWM plan is implemented for a community, the first means of attacking

The problem should be by the source reduction. This is an unfortunate terms because it is both

incorrect and misleading. One is not reducing sources but rather reducing the amount of waste

coming from a source and thus the term should be waste reduction.