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The book was composed by PreMedia Global, and printed and bound by It is intended to introduce students of engineering, physics, mathematics, computer. Our free eBooks in this category will help you prepare for your exams thanks to Engineering Mathematics: YouTube Workbook Foundation of Physics for Scientists and Engineers · Concepts Control Engineering Problems with Solutions. An e-book is a book that made available in digital format, consisting of text and images. There are many websites that offer free eBooks to download. In this.
A study in the application of statistics, probability and distribution to engineering. A study on semiconductor technologies and all aspects of semiconductor technology concerning materials, technological processes, and devices, including their modelling, design, integration, and manufacturing.
Electrical power is becoming one of the most dominant factors in our society. Power generation, transmission, distribution and usage are undergoing significant changes that will affect the electrical quality and performance needs of our 21st century industry.
One major aspect of electric power is A science textbook about electricity and magnetism that contains subjects on the theory of relativity, circuit laws, laws on electricity and magnetism, magnetic fields, motion, cyclotron, magnetic force and conductors. This book uses an index map, a polynomial decomposition, an operator factorization, and a conversion to a filter to develop a very general and efficient description of fast algorithms to calculate the discrete Fourier transform DFT.
The work of Winograd is outlined, chapters by Selesnick A book that focuses on the discrete fourier transform DFT , discrete convolution and particularly the fast algorithms to calculate them. These topics have been at the center of digital signal processing since its beginning, and new results in hardware, theory and applications continue to keep WIN the ultimate Audiobook experience!
Enter here no download necessary. Join Now Login. Sort by: Showing results: Sep Downloads: PDF, ePub, Kindle. Jan Downloads: Ability to describe the basic concept of noise pollution and solve basic calculations relating to it.
Ability to describe the related legislation on Environmental Quality Act Many of us are exposed to high levels of noise while at work, travelling, shopping, and where there can be intrusive noise from traffic, domestic appliances, and especially if you are living in badly constructed apartments or terraced homes, from your neighbours.
In general, noise can be defined as unwanted signals. To be more specific, noise is defined as unwanted sound. Therefore, noise can be considered as wrong sound at a wrong place and at a wrong time. Some people may find it tolerable, while others might find it annoying. Involuntary noise is noise that can be avoided. An example of involuntary noise is noise produced in a crowded area like a packed stadium. Voluntary noise is the noise which can be tolerated and the sufferer is normally being compensated.
For example, those who work at an airport have to tolerate aircraft noise. As such they are usually compensated with higher wages. In industrialized countries, noise is increasingly an environmental nuisance.
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It can interfere with human communication and sleep. Noise can also reduce the value of properties, e. Noise can also result in both physiological and psychological effects. Extremely loud and sudden noises cause pain to the ears and may cause temporary deafness or permanent damage to our hearing. High noise level of sufficient duration can result in temporary or permanent loss of hearing. Prolonged exposure to noises which are not extremely loud can also affect hearing to a certain extent.
Dangerous levels of noise come from industrial activities. Environmental noise intrusions such as traffic noise can interfere with communications, sleep disturbance and interfere with the ability to perform complex tasks. If the noise starts to spread out from air, it is called air-borne. If the sound starts from vibration between structures, it is caused structure-borne. The structure-borne noise occurs when building elements are in direct contact with the noise source. Sound waves are characterized by their frequencies, amplitudes and phases.
The quality of a sound is determined by its frequency. For people with good hearing, the audible range of frequencies is normally between 20 Hz and 20, Hz. In most practical noise control problems, however, it is possible to consider a rather narrower range of frequency, say 50 Hz to 10, Hz. Sound with frequency less than 20 Hz is called infrasound and sound over 20, Hz is called ultrasound.
However, most sound are not pure sinusoidal waves. They vary both in frequency and amplitude over time. To quantify their magnitude over the measured time T, the r.
Power, W, radiated by any acoustic source can be written as: For a point source, the noise is non-directional, and can be assumed as a spherical sound source. For a spherical sound source, the sound intensities at all points on the imaginary sphere surface are equal.
The acoustic intensity at a distance r m from the acoustic centre of a spherical sound source is: The maximum sound intensities at all points on an imaginary cylindrical surface sound source, is given by as: In an environment in which there are no reflecting surface, the r. Therefore, sound pressure of linear scale is an inconvenient way to represent these quantities is to use logarithmic scale. An appropriate reference quantity is required. As sound level is expressed in logarithm scale, they cannot be added directly.
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For quick estimation, table or figure can be used for addition of sound level. The Leq is a single value rating which has the same energy content as the varying sound level. As an example, sound pressure level cannot be used as an indication of loudness because the frequency of sound has quite a bit to do with how loud is the sound. For this reason, it is important for us to know the frequency of the noise we are measuring.
This contributes to the weighting networks. Weighting networks are electronic filtering circuit built into the meter to attenuate certain frequencies. They permit the sound level meter to respond more to some frequencies than to, something prejudicial like that of the human ear. The main different between these 3 networks are a very low frequencies are filtered quite severely by the A network, moderately by the B network, and hardly at all by the C network.
Therefore, if the measured sound level of a noise is much higher on C weighting than on A weighting, much of the noise is probably of low frequency. When the weighting network is used, the sound level meter electronically subtracts or adds the number of the decibels shown on each frequency from or to the actual sound pressure level at that reading. American National Standards Institute Example 2.
What is the corresponding SPL in dB? Example 2. Addition of Sound Level Four sounds from different sources are to be combined to obtain a total sound pressure level SPL. What is the total SPL. By using Table 2. Calculation of Leq Consider the case where a noise level of 90 dBA exists for 10 minutes and it followed by a reduced noise level of 70 dBA for 30 minutes.
What is the equivalent continuous equal energy level for the 40 minutes period? Assume 5 minute sampling interval. Calculation of Leq An employee in a timber mill uses a saw to cut timber into different length. While the saw is idle, it produces a level of 90 dBA at his work position.
When it cuts into timber, it produces a level of 95 dBA. An exposure of 8 hours per day is assumed. It carries both the sound pressure level and frequency. This follows from the variation in sensitivity of the ear with frequency. For this reason, measurement of SPL in dB is not a very accurate measure of loudness.
The ear is not equally sensitive to all frequencies. Sound entering the ear is continuously frequency-analyzed along the cochlear partition, acting as a number of narrow band filters. The ear is most sensitive from Hz to Hz.
The units used to label the equal- loudness are called phons. Since the ear is most sensitive to frequencies in the range 1 to 5 Hz, sound at these frequencies would be rate much louder than one at the same SPL at other frequencies.
The A weighting network is the most important network. The unit is dBA.
However, the dBA is a single figure rating. It does not provide information on the frequency content of a noise source.
Noise meters are classified as follows: It is recommended that type I instruments be used for industrial measurements and for environmental measurements involving legislation. A new IEC will replace the above standards. One major change is the abolishment of Type 3 noise meter. Fluctuations in level are common and sometimes the variations can be quite large.
To accommodate this phenomenon the sound level meter is provided with 2 types of responses: It is most suitable for workers that move between many different environments during the working day. If D is greater than 1, the exposure has exceeded the permissible limit.
In this respect, regulations with numerical limits of maximum permissible noise are currently not available. Whilst regulations with prescribes noise limits are not legally defined the Department of Environmental had issued guidelines on permissible noise limits in its course of enforcement of the Environmental Quality Act.
The noise limits that are often used are tabulated in Table 2. The guidelines for Siting and Zoning of Industries also give daytime and night time noise limits based on maximum sound levels according to the category of the industries. This requirement must be strictly adhered to at noise sensitive areas such as hospitals and schools. Approval of such EIA and the projects usually include maximum permissible noise limits at the affected areas that must be complied with during construction phase of the projects and upon operations of the projects i.
Noise limits similar to that tabulated in Table 2. There are provisions in the Environmental Quality Act for the control of sound propagated to the environment, affecting the community. The Department of Environmental is currently preparing guidelines for environmental noise control. These guidelines could then be enforced under the Environmental Quality Act and would be used in Environmental Impact Assessments, by the local authorities, and for planning proposes.
Noise measurement and assessment procedures are to be also included. Ability to describe basic concept of solid and hazardous waste and solve basic calculations on this area. For example, there were sites in ancient Rome which were pits where carcasses, animals and humans, were dumped. Cities from the Bronze Age such as Troy were actually raised in levels as garbage became unbearable. Clay layers were spread over the garbage, just as in modern tips.
Scavenging was one of the first forms of recycling and "rag and bone men" such as Steptoe and Son were just recyclers. The idea of scavenging was so bad to society that in the City of London outlawed the practice which is now an important part of the waste management industry.
Historically, links between wastes and health have been another important catalyst for change. A study in the mid 19th century demonstrated a link between sewage disposal in the Thames River and the incidence of cholera epidemics.
This was 30 years before the cholera bacteria were even identified. Some of the earliest waste disposal schemes were established in order to escape the health problems associated with the industrial revolution including the development of garbage collection, street cleaning, and sewage collection schemes. Another early waste treatment which moved from Europe to USA was to stew garbage and dead animals in large vats.
This produced grease and 'residuum' which was a black gooey material. The grease was used for the manufacture of candles, soap, lubricants etc, and the 'residuum' was used as plant fertiliser.
The other wastes from this process were runoff into streams. This process was stopped in Europe in the 's but continued in the USA until the 's. Incinerators were developed in the s in England, and with the industrial development incinerator technology improved. Waste management in Malaysia displays an array of problems, including low collection coverage on average due to the inaccessibility by vehicles of some areas, irregular collection services, inadequate equipment used for waste collection, crude open dumping and burning without air and water pollution control, inadequate legal provisions and resources constraints.
These problems are caused by various factors which have an impact on the development of effective waste management systems in Malaysia. Institutional constraints are among these problems. Even though several agencies like the State Department of the Environment and municipal councils are involved in waste management, they often have no clear functions in relation to waste management and there is no single agency designated to coordinate their projects and activities.
The lack of coordination among the relevant agencies often results in duplication of efforts in waste management, wasting of resources, and un-sustainability of overall waste management programmes. In the developing countries, waste management is becoming an acute problem as urbanization and economic development increase leading to larger quantities of waste materials requiring management in these countries. In Asia, the management of waste materials requires immediate attention especially in countries such as China, South Korea and Malaysia which have been categorized as emerging industrialized countries.
In , the urban areas of Asia produced about , tons of municipal solid waste MSW or approximately 2. In , this figure is estimated to increase up to 1.
Table 3. Countries with low incomes have the lowest waste generation rates, averaging 0. High income countries such as Korea, Hong Kong, Singapore and Japan, tend to have higher waste generation in comparison to other countries.
In Hong Kong, the generation rate is among the highest due to intense construction and demolition within the municipality WB, The amounts of waste in Japan and Singapore are lower but that is also due to the fact that the data do not include all municipal waste generated within these countries.
The characteristics of MSW vary from one country to another and the solid wastes of rural towns in Asia are significantly different from those of large cities, having more organics but few plastics from packaging or food wastes UNEP, There are also varying legal definitions of waste leading to differences in what is considered to be waste.
In general, waste is defined as any material which is unwanted by the holder and intentionally thrown away for disposal. This does not exclude that certain wastes may eventually become resources valuable to others once they are removed from waste stream WB, Malaysia, with a population of 24 million, is facing an increase of the generation and accumulation of waste.
This development is causing social, economic and environmental problems at a significant level. Individuals, industries, municipals, state and federal governments are concerned because improper waste management leads to health problems for local communities.
Moreover, poor visual appearance has negative impacts on official visits and tourism. These problems are particularly serious in areas where intensive urbanization and population concentration lead to an increase of solid wastes and to a decrease of available land suitable for disposal. World Bank. What a Waste: Solid Waste Management in Asia. May Malaysia, like most of the developing countries, is facing an increase in the generation of waste and of accompanying problems with the disposal of this waste.
Overall, the local communities generate 16, tons of domestic waste per day and the amounts per capita vary from 0. On average, waste generation is about 1 kg per capita per day GAIA, Waste is grouped into three different categories in respect of disposal —solid waste, medical waste and hazardous waste. According to a study by E. Roundtable on Urban Solid Waste Management. Incinerators were redesigned to allow more efficient energy production. At the same time there was an increasing awareness of environmental problems with a consequent upsurge in environmentally friendly practices including waste minimisation, waste recycling, and control of hazardous waste discharges.
One view of waste management is shown in the Figure The problem with this diagram is that it does not include waste minimisation or risk assessment procedures.
These impinge on all the processes shown. This diagram also provides a framework for much of the material we will cover in Waste Technology. Tchobanoglous, This refers to an arrangement or ranking of waste management actions which can usually be carried out in the community.
At its simplest level you are probably familiar with "Reduce Reuse Recycle" This is a ranking of actions - we should reduce the amount of wastes produced as the first option. The next option is to reuse what wastes are produced, e. The third option is to recycle material, e. This is depicted in Figure For example Figure shows a waste management strategy or hierarchy in which there has been a change from lower technology landfill disposal to higher technology recycling etc.
This has also led to an increase in waste minimisation. Tchobanoglous, There are other similar strategies. Source reduction ii. Recycling reuse and recycling wastes iii. Treatment - destroying, detoxifying or neutralising wastes iv.
Disposal - discharging wastes. Other schemes utilise the 3 R's; Reduce, Reuse, Recycle. It can be seen that there is some overlap in these ideas - some common features, but they are very sketchy plans. When trying to plan waste management we are dealing with people, and planning any human activity is a complex process.
That is why we need to have relevant legislation. The term municipal solid waste MSW is often found in the literature. It generally implies all the wastes generated in a community with the exception of industrial process wastes and agricultural solid wastes. Waste composition is used to describe the individual components that make up a solid waste stream and their relative distribution, usually based on percentage by weight.
This is usually determined by a waste composition study. Waste composition is likely to change because of changes in lifestyle, increased recycling, education programmes, and changes in collection systems. Wastes are classified based on their composition. The National Waste Database Classification scheme should be used to ensure a standard approach. It does not include food processing wastes from canneries, slaughterhouses etc.
Garbage originates mostly from domestic kitchens, stores, markets, restaurants etc Rubbish consists of combustible and non-combustible solid wastes from homes, stores and institutions but does not include garbage. The term trash is often used in the same way but is probably more a subset of rubbish.
The combustibles consist of paper, rags, wood, tree branches etc. Residential and commercial solid wastes, excluding special and hazardous wastes, consist of organic and inorganic solid wastes from residential areas and commercial establishments. Typically the organic wastes include food waste also known as garbage , paper, cardboard, plastics, textiles, wood, yard wastes etc.
The inorganic fraction includes glass, metals - ferrous and non ferrous e. If the waste components are mixed, then it's referred to as commingled MSW. Wastes that decompose fairly quickly, e. Non-industrial refineries, chemical plants, wastes including food wastes, power stations, demolition etc rubbish, ashes, demolition and construction wastes, special wastes, hazardous wastes Agricultural Crops, orchards, dairies, Spoiled food wastes, agricultural feedlots, piggeries, farms etc wastes, rubbish, hazardous wastes Source: If we know how much waste is generated, we can then design management strategies to handle reduce, reuse, recycle etc those wastes.
This sounds very good in principal, but the problem is we do not have very good figures on amounts of wastes being generated. The actual composition of the wastes generated is another problem of definition. Figure shows the composition of the Malaysia domestic waste stream. Hassan, There are also variations depending on the source of the wastes - residential versus commercial wastes. For example, the recent waste audit in Muar showed that food wastes made up There are also variations over time as waste management has changed.
Another important aspect of waste composition is the composition of recyclable material in MSW. Most of you are familiar with recyclable materials such as plastics, glass, metals etc.
Substantial recycling is taking place in Malaysia which marks the future changes in waste composition. This requires some sort of classification system. Classification is usually into hazardous and non hazardous classes, but could be extended to include recyclable versus non recyclable. Of the 12 tonnes of raw produce,10 tonnes become products,1.
Stored separately, the damaged cans are recycled. Assume the materials separated for recycling and disposals are collected daily.
Prepare a material balance for the cannery on this day and a material flow diagram accounting for all of the materials. Also determine the amount of waste per tonnes of product. Step 1: On the given day, the cannery receives the following: Step 2: As a result of internal activity: Step 3: Determine the amount of waste per tonne of product: These are important for the management of waste disposal and for the recovery of a range of materials, including energy.
It is important to note this information is distinctly important to determine the method of MSW disposal such as composting, landfills, recycling etc. The important physical properties of MSW include density sometimes referred to as specific weight , moisture content, particle size and distribution, field capacity, and porosity. Density varies because of the large variety of waste constituents, the degree of compaction, the state of decomposition, and in landfills because of the amount of daily cover and the total depth of waste.
Inert wastes such as construction and demolition materials may have higher densities, and density can change as in landfills where the formation of landfill gas and decomposition may bring about significant mass loss. Density is important because it is needed to assess the total mass and volume of waste which must be managed. The density of MSW is often referred to as loose, as found in containers, un-compacted, compacted etc. Density varies not only because of the type of treatment it gets collection vs.
Some typical density values are presented in the Table Agumuthu, Moisture content is important in regards to density as above , compaction, the role moisture plays in decomposition processes, the flushing of inorganic components, and the use of MSW in incinerators. Pre-treatment of waste to ensure uniform moisture content can be carried out prior to landfill disposal. The wet weight moisture content can be determined using the following equation: Tchobanoglous et al.
For example, ferrous items which are of a large size may be too heavy to be separated by a magnetic belt or drum system. The size of waste components can be determined using one the following equations: It is a critical measure because water in excess of field capacity will form letéléchargemente, and letéléchargemente can be a major problem in landfills.
Permeability depends on the other properties of the solid material including pore size distribution, surface area and porosity. This is especially important where wastes are burned for energy recovery, in which case the four most important properties are proximate analysis, fusing point of ash, elemental analysis, and energy content. Elemental analysis is also important in determining nutrient availability. Some typical values are shown in Table Because of concern about halogens these are also often determined as well.
The results of this analysis are used to characterise the composition of the organic matter in wastes. Typical values are shown in Table The energy content will be looked at later when discussing on incineration. Of most importance are the major nutrients in their various forms - nitrogen as nitrates, ammonium N phosphorus and potassium.
Example Using the data given in Table The most important biological characteristic of the organic fraction of MSW is that almost all the organic components can be converted biologically to gases and relatively inert organic and inorganic solids. The production of odours and the generation of flies are also related to the putrescible nature of the organic materials.
These will be discussed when talking about landfill processes. Solid wastes can be transformed by physical, chemical and biological means Table It can include such things as magnetic separation.
The usual materials recovered include separation of recyclables, the removal of hazardous wastes, and the recovery of energy products. Volume reduction refers to the processes whereby waste volumes are reduced, usually by force or pressure. Collection vehicles frequently have compaction mechanisms - or compaction can take place at a transfer station.
The baling of plastics, paper, and aluminium is another means of volume reduction, as is the compaction that takes place in landfills. Pressure can be used, e. Size reduction is used to reduce the size of wastes.
It usually involves some form of shredding, grinding or milling. The main processes are combustion, pyrolysis, and gasification. Combustion is the chemical reaction with oxygen of organic materials accompanied by the emission of light and heat. The process can be represented as: These processes will be examined in more detail later in the course. When carried out anaerobically methane is produced - a typical component of landfill gas.
This will be examined in more detail later. Typically waste transformations are used: The different types of systems mentioned, not only for waste collection but also for the collection of recyclable materials is varied and governed by many factors some of which have nothing to do with waste management. It meant choosing the most appropriate trucks, designing collection routes, and then administering the collection.
With present day emphasis on recycling and composting the need to segregate materials has become most important.
It can mean different vehicles collecting different material and taking it to different locations. As a result, the collection of wastes has become more complex and more expensive.
To meet current needs there is a call for the development of an 'integrated collection strategy' which incorporates the following: Collection frequency may have to be altered because of weather conditions which can pose health and odour problems. Increasing collection frequency has considerable cost implications and could lead to doubling of labour costs.
Bins are placed near the curb side thus allowing the use of one-person vehicles with extending arms to collect the bins. In some locations, e. This means extra crews are required with extra labour costs.
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In some locations the crew actually come into the house yard often around the back to collect the bin. This obviously slows collection times and increases costs.
The use of centralised systems, such as apartment blocks, will accelerate collection times by reducing travelling distances and times. Each type has advantages and disadvantages and must also be related to the set out location.
For instance, large wheelie bins will be impractical in narrow urban areas with on-street parking. In New Zealand there is another advantage with bags in that in some districts a special sticker is required to be placed on the bag for costing purposes.
Stickers can be easily seen by collection crews. The use of paper bags can provide advantages in composting in that they are easily shredded. The disadvantages of wheelie bin are one of size - most people put out more rubbish to fill the bin. They also require mechanical lifting arms for health and safety reasons, and cost more initially.
Interestingly, most wheelie bins are made out of recycled plastic. The set out location, size of area to be served, method of collection and costs of vehicles and operators are the major concerns.
In most instances, curb side pickup is the most convenient, and the trend in recycling is towards some form of curb side pickup. Drop-off and download-back centre are not as convenient. Typically, a programme using such centre will have lower participation rates. Most communities and hauling companies face a dilemma in deciding how best to collect recycled materials, especially those with fleets of refuse vehicles. The prospect of replacing a fleet of refuse trucks with an equally expensive fleet of vehicles designed for recycling is normally not economically feasible, at least at first.
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As a result, most recycling programmes try to use existing refuse equipment to collect recycled materials. Many innovative ideas have been used to convert refuse trucks to all-purpose refuse collection and recycling vehicles. For example, the city of Madison, Wisconsin, designed a newspaper rack welded to the frame of refuse trucks for the purpose of collecting bundled newspaper.
This low cost adaptation was first designed by city engineers in and is still in use today. The split-bin system in use in Byron Bay is a high-cost method, necessitation new bins and new collection vehicles. In the UK in Luton, a system using cuphooks attached to bins was tried unsuccessfully.
Some companies which haul waste from commercial accounts generating high volumes of office paper or cardboard make no attempt to separate the material. Instead, they substitute back- end sorting and processing for separation before collection, separating recyclables out of the waste stream at a processing centre in what is known as "dump and pick" operation.
Some of these operations have proved successful, although contamination of recycled materials from mixing with other waste can be a problem. Other communities use refuse trucks in concert with pickup trucks. The pickup follows the large vehicle and collects recycled materials on the same day as normal refuse pick-up.
By requiring the use of clear plastic bags for recycled materials - and perhaps supplying them - the mixing of recycled materials with other refuse can be minimised. In still other communities, recyclables are collected on a different day. As long as public education is continuous, and the pick-up schedule is highly reliable, the public seems willing to follow whatever schedule is established for collecting recyclables.
The vehicle use for collection will generally have as many compartments as are required for the different types, usually 3 or 4.
These are sorted by the crew at collection and obviously this involves more labour costs. This system can be varied, e. Sometimes this can also involve a preliminary sorting, e. A disadvantage is the problem of contamination, especially in a single compartment system.
A further disadvantage is that compaction cannot be carried out as well with a loss in efficiency. This is obviously a labour intensive operation, though some materials, e. Already, many communities and waste-service companies use compartmentalised trucks or trailers on collection routes. There are a variety of vehicle designs on the market, all of which provide efficient and easy loading and unloading of both recovered materials and solid waste.
Some communities using special recycling vehicles have enhanced participation rates and collecting efficiency by supplying recycling boxes to homeowners. Similar programmes exist in cities such as Santa Rosa, California, and St.
Louis Park, Minnesota, where residents have received stacking plastic containers for paper, glass, and cans from the city or contractor. Mobile download-back operations are also increasing in number, especially for service of rural areas - which may not produce enough volume to support a private recycling operation.
Mobile download-back units often pay for some materials and accept for free other materials. Here it is separated, processed, and stored until enough material has been collected to create a full load for transport to a market. Material usually must be processed to meet the specifications of downloaders. The centre must be designed to efficiently move the material from the tipping floor or drop-off point through the system to the storage area. Many technologies are available for efficient processing, materials handling, and storage.
The choice of equipment and systems must take into account: Glass, which is impervious to weather, can be stored outside; this would require the construction of revetments or concrete storage containers, which is relatively cheap. Collected glass can be dumped into the revetment compartment or removed by a small tractor.
A barrier is often placed at the front of the revetment to ensure that injuries to employees or others do not occur from accidental spillage. Some materials, such as newsprint, cannot be stored outside in the weather indefinitely; to achieve a competitive price for newsprint, one must prevent decomposition.
Storage indoors of newspaper and other items can create problems for a poorly designed centre, as there can be a constant struggle between space needed for processing and operations and space requirements for materials storage.
What's more, storage problems can result when either the volume of recycled materials expected is significantly underestimated or the demand for materials already on hand is significantly overestimated. The amount of processing which will be necessary at the recycling centre will depend to a large degree on how the material is collected.
So-called "dump and pick" operations require significant manual labour for extraction of recycled materials from the bulk of the refuse.
While some of these operations have workers hand-sort material, hand-sorting can be dangerous for workers, exposing them to hazardous materials and sharp objects contained in the waste. Some operations utilise sophisticated sorting technology, including trommels, air classifiers, and conveyers to mechanically separate the waste. Where waste volumes collected are large, mechanical separation systems may be economic. Even with these systems, some hand-separation is usually needed to ensure recovered materials are free of contamination.
Material that enters the recycling centre already separated is much easier to handle. Processing is generally performed for one of two reasons: Equipment is normally needed only to move material from one processing station to another or from processing to storage. It can be used to place recovered materials newsprint, cardboard, plastic, and aluminium in large agglomerations which can be easily moved and are stackable.
Since paper, cardboard, and plastic bottles can comprise a high percentage of a municipal waste stream, most recycling operations will need a baler to process this material. Baler types should be carefully investigated. Operations providing bulk newsprint to paper recycling markets may choose a baler which makes bales of approximately 1, pounds each. On the other hand, a centre selling shredded newsprint for animal bedding to local farmers will need a hay baler, which makes small 70 pound bales.
For maximum flexibility, perhaps both types of balers should be utilised, if sufficient space is available. The question of what type of baler will be best for an operation is just one example of the need to do some homework before getting started.
Other processing equipment may be needed to satisfy downloader specifications and provide sufficient compaction to allow for cost-effective transport. A centre may use shredders, shears, grinders, and crushers.
Each piece performs a different function but all have the objective of reducing waste volume. For example, there are a variety of shredders available, which will shred paper, cans and even automobiles.
Glass crushers reduce bottles into a mixture called cullet, which is the form most attractive to glass recycling markets. Solid waste is an abrasive and caustic material, which makes proper maintenance of waste processing equipment very important. Moreover, operating this equipment can be dangerous; special training and safety precautions may be required.
Power needs can also be high. Consequently, processing's potential benefits must be carefully weighed against its cost and operational considerations. Recycling centres may not require drive-on scales, if volumes received are small or the need to move and process material quickly is not great. Note that a recycling centre operated in conjunction with a landfill or transfer station might be able to use the disposal facility's scale.
Where manual sorting is used, a conveyer system, often coupled with a magnet to collect ferrous, provides a good way to move material from the tipping floor to other processing stations. After processing, material is often stored in large cardboard boxes, known as "gaylords," or in other similar containers.
download of backup transport equipment should also be seriously considered. The inability to move material from processing to storage caused by a lack of backups could create a serious disruption in the recycling operation. In designing a recycling centre, sufficient aisle room is a must.
Designers must allow for easy and efficient movement of transport devices. A convenient loading dock, readily accessible to large trucks, is important; it should provide protection from inclement weather. Material storage areas must be located close to the loading dock.
Employee facilities and an office for record keeping and centre operations should also be carefully planned. Local building codes likely will mandate these and other features of the recycling centre. Improper past disposal practices have caused environmental degradation, need for costly remedial actions, and public opposition to the siting of new facilities. In some areas of the country, waste is being hauled hundreds of kilometres as communities search for disposal options.
For example in California, the Napa Valley wastes are transferred by rail across three states to the landfill disposal site, a distance of km. Until recently, managing waste was primarily a local matter. Now, both the federal and state governments are beginning to impose stricter regulations on design and operation of facilities that manage or dispose waste. Protecting the public from the potential environmental and health impacts of poor waste management practices has become a national mandate.
Improved technology for collecting, processing, and disposing waste is being demanded by the public. Unless the future proves that our society can manage waste better than in the past, public opposition will continue to grow, costs will continue to rise, and the call for tighter and tighter restrictions will grow louder.
At the heart of the debate is the landfill. Because old landfills were developed more to provide cheap disposal alternatives than to protect the environment, many have leaked. But newer landfills are designed to contain waste products and to protect the environment over the long term. Although other methods of managing waste, including recycling, composting, and incineration, are being instituted by communities around the country, access to a landfill remains a necessity for everyone.
With the emphasis on waste minimisation and full cost recovery of waste management, along with more rigorous environmental requirements many communities around the country will face for the first time the need to construct state-of-the-art landfills. This course will describe the basic principles involved in developing and operating a state-of-the-art landfill.
In a landfill, solid wastes are disposed of by spreading in thin layers, compacting to smallest practical volume, and covering each day, or periodically, with soil or suitable substitute material in a way that minimises environmental problems. A landfill's design life extends many years beyond the time when it is closed. Waste stabilisation begins shortly after it is placed in the landfill, but will not be completed until years after closure.
Care must be exercised to ensure that an environmental problem does not develop during operation or after closure. Careful design, construction, and operation can minimise the potential for problems arising at a landfill. Recently, many questions have been raised about the long-term impacts associated with land filling. Site selection and approval has proven very difficult due to neighbour and political concerns. Questions regarding the eventual disposition of the landfill materials had resulted in renewed interest in decomposition processes and biodegradability.
These special topics will be addressed later. In the trench method the excavation into which the landfill is placed is excavated specifically for the purpose of land filling. The soil is temporarily stockpiled.
The waste is placed on the ground surface or, more commonly, a landfill liner, spread in layers, and driven over with compaction equipment. Successive layers are built up until a depth of 3 to 4 m is achieved see Figure The cover material my be soil or a synthetic material and is usually placed at the end of each day's operation, or more frequently.
Possible exceptions to this procedure are when limited equipment availability at small sites results in less frequent covering, or when a large site operator continuously fills the area, in which case cover may not be required. A completely covered compacted solid waste unit is called a cell. A cell's width depends on the number of vehicles unloading solid waste at a given time. The width of the working face can be increased to accommodate vehicles unloading side by side. However, if the working face is too wide, nuisance conditions may develop.
A good practice is to keep the working face as small as possible. A series of adjoining cells, all the same height, makes up a lift. The completed fill consists of several vertical lifts which may extend 20 to 50 m above the original ground surface. The final cover for the landfill will be about 1 m of soil or a combination of soil and synthetic materials.
The function of the final cover is to limit the entry of water into the landfill. This results in reduced letéléchargemente generation, that is, the release of contaminated liquids from the base of the waste in the landfill. Limiting the entry of water, however, greatly slows decomposition; thereby extending the time period before the waste is finally stabilised and environmental monitoring of the site can cease.
The area method is shown in Figure This is used when the terrain or soil conditions are such that cells or trenches cannot be dug. Site preparation can include the use of liners and letéléchargemente control systems. Figure The Area Method of Landfill The canyon method is similar to the trench method except natural depressions or canyons are used rather than digging trenches.
It depends upon the area covered, the depth of the waste, and the ratio of waste to soil or synthetic cover. The air space within the landfill is the volume available into which solid waste and cover may be placed. The tonnage of solid waste which can be land filled in a given air space will increase as the quantity of soil cover is reduced by better construction practices or the substitution of synthetic materials and the compaction of the solid waste is increased.
Waste-to-soil ratios of 4: Probably the biggest advantage of sanitary landfills, when compared to open dumps, is the protection of public health and the environment. The major objections to sanitary landfills are initial costs for design and construction, public opposition when siting, and increasingly, the concern for recovery of material instead of disposal. Example 3. A community of 50, people uses a 12 hectare landfill site that can be filled to an average depth of 20 m.
If MSW is generated at a rate of 2. Due to less than ideal conditions in a landfill, the observed gas yields are about cubic metres per tonnes of waste. Other 'bulk' components of landfill gas those gases measured at percentage levels include hydrogen, oxygen and nitrogen. The relative proportion of these gases, together with key trace components often falls within a range that is characteristic of gases from different sources, and can help to identify the source of migrating gas.
Table shows some typical values of landfill gas composition as well as some recorded maximum levels. Heiss-Ziegler and Leachner, Both methane and hydrogen are flammable in the presence of oxygen and are therefore potentially explosive if ignition occurs within a confined environment.
The exact values for the upper explosive limit U. L and lower explosive limit L. Methane is non-toxic, but through displacement of oxygen within the root-zone, may cause death of surface vegetation. Where landfill gas migration has occurred, the migration pathway can often be followed by visual observation of the surface vegetation, including trees, which show withering at leaf margins, defoliation, and branch dieback.
In extreme cases, surface heating of the soils can also be detected. Whether these surface-heating effects are a result of heat transference from the warm gas or a consequence of biological methane oxidation is not clear. In the latter case, the methane oxidising bacteria utilise the methane for bacterial growth, releasing carbon dioxide as an end product and some consideration has been given to the use of such bacteria in landfill gas control systems. Carbon dioxide is an asphyxiate by virtue of oxygen displacement, and can cause deaths due to paralysis of the respiratory centres.
The threshold limit value for CO2 is 0. Oxygen and nitrogen are usually present in landfill gas due to mixing with atmospheric air. Nitrogen is essentially inert and will have little affect except to modify the explosive range for methane, and although oxygen deprivation will result at the levels normally found in landfill gas Table it is difficult to envisage a situation where anyone would find themselves in an environment of 'pure' landfill gas.
In many cases the level of oxygen within a gas collection system is used to monitor abstraction rates, and to control the rate of pumping. In addition to the hazards associated with the major 'bulk' gases the minor trace components may also exert a deleterious impact upon the environment and upon human health.
Many of the trace compounds in landfill gas are recognised toxicants when present in air at concentrations which exceed recognised toxicity threshold limit values TLV's or the Occupational Exposure Standards OESs set by the Health and Safety Executive. Anyone coming into contact with landfill gas is therefore potentially at risk from the toxic nature of the minor components. For gas migration to occur there must either be a concentration gradient to allow diffusion in the gaseous phase diffusive flow , a pressure gradient viscous flow or a combination of both.
Gas diffusion is the process by which matter is transported from one part of a system to another as a result of random molecular movement, and the rate of gas diffusion is inversely proportional to the square root of its density.
Thus a 'light' gas such as methane will migrate 1. The method of filling is the most important factor affecting within site gas migration. Thin layer techniques utilising good compaction and dally cover will tend to encourage lateral gas migration, especially where the cover materials are of low permeability.
Conversely, the construction of wells within the site will tend to favour vertical gas migration within and around these structures. During landfill development, any gas produced will vent via the pathway of least resistance. Therefore prior to final capping and assuming that only permeable intermediate cover has been used, most gas produced will vent to atmosphere.
However, after final capping, gas venting to the atmosphere will be limited according to the effectiveness of the cap. As a result, gas pressure will develop within the landfill creating a driving force for gas migration. Under these conditions, the possibility of the lateral migration of gas increases and the rate and extent of migration will depend upon a number of factors including environmental, climatic and geophysical conditions.
Environmental factors are essentially restricted to conditions within the waste and will affect the rate and extent of waste degradation and hence affect the rate and extent of landfill gas pressure build up. Geophysical conditions will affect the gas migration pathways; faulted and fractured strata and strata of varying gas permeability will affect the direction and rate of gas movement and can be modified by hydro-geological factors such as water table levels.
Gas may travel large distances through such strata and once at the 'surface' may enter surface structures resulting in a potentially explosive situation. At sites lacking gas control measures, landfill gas has migrated to metres beyond the site and indicates that there is no safe distance from a landfill site. The gas may migrate through permeable strata, caves and cavities, fissures, mineshafts, sewers, drains, tunnels, and other features that create a path of least resistance to gas movement.
Climatic conditions including atmospheric pressure and rainfall can also affect landfill gas migration; as atmospheric pressure falls, the surface pressures opposing gas migration decrease thus facilitating gas movement. The pressure differential between the landfill gas and atmospheric pressure is therefore important, and an inverse relationship a between atmospheric pressure and gas migration measured as methane concentration at off-site monitoring points can be demonstrated at a number of landfill sites.
Rainfall can affect gas migration through its effects on surface sealing, by causing surface materials to swell and close surface cracks, thus reducing vertical migration pathways with a resultant increase in lateral gas migration. Water infiltration can also increase water table levels outside the landfill and letéléchargemente levels within the site, thus reducing the gas volume and increasing gas pressure. Estimate the theoretical total volume of gas of STP that will be generated in a sanitary landfill by anaerobic digestion of kg of MSW, given that the waste can be represented by the chemical formula C70 H O45 N.
If leakage does occur, an underlying groundwater aquifer may be contaminated. The extent of contamination will depend upon the permeability of the soil formation. Leakage into a porous formation may result in a large area being contaminated. In the past, many landfills were not lined.
Due to groundwater protection concerns, liners are being installed at the base of most new landfills to control and collect the letéléchargemente.
Some inorganic materials will still be solubilised into the letéléchargemente by decomposition occurring during the second stage, so the fall in conductivity will not be as drastic as the fall in COD. After the readily degradable organic material has been broken down, methane production will decrease and more aerobic conditions may be established by incoming oxygenated water.
Actual landfills may vary considerably in the rates at which decomposition occurs. For example, the aerobic pH may last a few weeks or months with significant methane generation occurring within one to two years. Additionally, a single landfill may have different parts in different stages of decomposition, with the gas and letéléchargemente composition reflecting the three stages.
Second stage decomposition takes several years or perhaps decades to complete. Landfill letéléchargemente is comprised of the soluble components of waste and the soluble intermediates and products of waste degradation which enter water as it percolates through the waste body. The typical analysis of landfill letéléchargemente is shown in Table Heiss-Ziegler and Leachner, The amount of letéléchargemente generated is dependent upon a number of factors such as water availability, landfill surface conditions, refuse state and conditions in surrounding strata.
With regard to public health and environmental protection, a properly designed and operated landfill will offer advantages in the following areas: Making the site pleasing to look at, while largely cosmetic, is not frivolous.The characteristics of MSW vary from one country to another and the solid wastes of rural towns in Asia are significantly different from those of large cities, having more organics but few plastics from packaging or food wastes UNEP, Phase out production and consumption as soon as feasible of halons and such chemicals as carbon tetrachloride and methyl chloroform that also contribute to ozone depletion.
Fluid power is used in a vast range of applications and power levels. In the field of particle technology hydrodynamic modelling in the form of CFD or DEM is an area with increasing focus in terms of modelling approach to granulation processes.
The different types of systems mentioned, not only for waste collection but also for the collection of recyclable materials is varied and governed by many factors some of which have nothing to do with waste management. Gaseous pollutant is the formless fluids that completely occupy the space, into which they are released, behave more like air and do not settle out. By requiring the use of clear plastic bags for recycled materials - and perhaps supplying them - the mixing of recycled materials with other refuse can be minimised.
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