sources and types of solid wastes

8/14/2019 Sources and Types of Solid Wastes

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Treatment

Typical components of municipal systems for source separation and materialsrecovery in industrialized countries are:source separation of different categories of waste from households, offices, shops,and institutions; collection at the curbside or drop-off by generators at bins or centers is subsidized by the government or private industries;collection of organics (kitchen and garden wastes) for large-scale composting; promotion of backyard composting through education and sometimes the provision of a small compost bin; and public subsidization of extensive and varied educational campaigns to sustain participation in all aspects of waste reduction.

In many industrialized countries, source separation and curbside collection programs are heavily subsidized by municipal governments, private industries or foundations. When municipal funding is withdrawn, the scope of materialsrecovery may be greatly reduced. These countries usually have the institutionalcompetence and capacity in urban government to integrate local and regionalwaste management plans. Citizens tend to be highly aware of the problems and tocooperate in separation programs. Undeveloped or fluctuating markets for recyclable materials, however, continue to limit cost recovery and the diversion of materials from landfills.

Developing countries

Most urban places in the developing world have yet to experience the decline of traditional recovery of recyclables and the corresponding increase in post-consumer wastes, which, together with scarcity of dump space, have led manyaffluent cities to sponsor materials recovery.

The engines of waste recovery and recycling in the poorer countries include:scarcity or expense of virgin materials, the occurrence of absolute poverty, theavailability of workers who will accept minimal wages, the frugal values of evenrelatively well-to-do households, and the large markets for used goods and

products made from recycled plastics and metals. Wastes which would beuneconomical to recycle or of no use in affluent societies have a value (e.g.,coconut shells and dung used as fuel). If one takes into account the use of compostfrom dumps sites as well as materials recovery, in countries like India, Vietnam,and China, the majority of municipal wastes of all kinds are ultimately utilized.

Waste reduction that could be achieved by legislation and protocols (such asagreements to change packaging) is not, at present, a high priority in thesecountries, although some are now moving in this direction. Because unskilledlabor costs are low and there is a high demand for manufacturing materials,manufacturers can readily use leftovers as feedstock or engage in waste exchange.

Residuals and old machines are sold to less advanced, smaller, industries. Public


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health is benefitting from plastic and boxboard packaging that reducescontamination of foods, and much of the superior packaging is recovered andrecycled. This tumbler is used for making pulp from waste paper. This small recyclingfacility is typical of many others throuthout India.(credit: Warmer Bulletin)

In offices and institutions, cleaners and caretakers organize the sale of paper, plastics, etc. At the household level, gifts of clothes and goods to relatives,charities, and servants are still significant in waste reduction. All cities and townshave markets for used goods. The greatest amount of materials recovery isachieved through networks of itinerant buyers, small and medium dealers, andwholesaling brokers. The extent to which the waste trading enterprises areregistered (formalized) varies in developing regions: in Latin America andAsia there is more formal registration than in Africa. The system is adaptive tomarket fluctuations, as the lowest level workers form a dispensable labor cushion:they must find other work, if they can, when there is reduced demand for thematerials they sell.

Because so many people are engaged in the activities of materials recovery, processing, and recycling, and alternative work is scarce, governments and socialwelfare organizations are often more sensitive to employment needs than toenvironmental considerations in waste management. Thus, they are prepared totrade off some environmental and public health risks against employmentgeneration.

The accompanying box shows the main paths traveled by wastes in Bangalore,due, in large part, to the activities of informal traders and recyclers.

Advantages of scarcity and frugal valuesFrom the point of view of waste reduction, the traditional practices of repair andreuse, and the sale, barter, or gift of used goods and surplus materials, are anadvantage to the poorer countries. Quantities of non-organic post-consumer wastes would be higher without them.

These societies should be alert to socio-economic changes that threaten resource-conserving traditions. When standards of living rise, voluntary source separationtends to decline, unless (a) it is encouraged through an incentive program or (b)the opportunities for waste generators to sell recyclables remain very convenient.Small waste trading enterprises which provide convenient redemption centers for

households, shops, and itinerant buyers are adversely affected by rising land


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prices, more high-rise accommodation, traffic regulation and NIMBY (Not In MyBack Yard) objections. Imported, high quality recyclables can undercut the marketfor local materials resulting in a decline of waste recovery.When economic motivations for separation and sale decline, public educationshould foster environmental and charitable motives for waste reduction.

Composting is the aerobic decomposition of biodegradable organic matter, producing compost. (Or in a simpler form: Composting is the decaying of food,mostly vegetables or manure.) The decomposition is performed primarily byfacultative and obligate aerobic bacteria, yeasts and fungi, helped in the cooler initial and ending phases by a number of larger organisms, such as springtails,

ants, nematodes and oligochaete worms.Composting can be divided into home composting and industrial composting.Essentially the same biological processes are involved in both scales of composting, however techniques and different factors must be taken into account.

Incineration is a waste treatment technology that involves the combustion of organic materials and/or substances.[1] Incineration and other high temperaturewaste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into incinerator bottom ash, flue gases, particulates, and heat, which can in turn be used to generate electric power. Theflue gases are cleaned of pollutants before they are dispersed in the atmosphere.

A landfill , also known as a dump (and historically as a midden), is a site for the disposal of waste materials by burial and is the oldest form of waste treatment.Historically, landfills have been the most common methods of organized wastedisposal and remain so in many places around the world.

Landfills may include internal waste disposal sites (where a producer of wastecarries out their own waste disposal at the place of production) as well as sitesused by many producers. Many landfills are also used for other waste

management purposes, such as the temporary storage, consolidation and transfer,or processing of waste material (sorting, treatment, or recycling).

A landfill also may refer to ground that has been filled in with soil and rocksinstead of waste materials, so that it can be used for a specific purpose, such as for building houses. Unless they are stabilized, these areas may experience severeshaking or liquefaction of the ground in a large earthquake.

Site construction requirements

The construction of a landfill requires a staged approach. Landfill designers are primarily concerned with the viability of a site. To be commercially and


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environmentally viable a landfill must be constructed in accord with specificrequirements, which are related to:LocationEasy access to transport by roadTransfer stations if rail network is preferredLand valueCost of meeting government requirementsLocation of community servedType of construction (more than one may be used at single site)Pit - filling existing holes in the ground, typically left behind by miningCanyon - filling in naturally occurring valleys or canyonsMound - piling the waste up above the groundStabilityUnderlying geology Nearby earthquake faultsWater tableLocation of nearby rivers, streams, and flood plainsCapacity The available voidspace must be calculated by comparison of thelandform with a proposed restoration profile.This calculation of capacity is based on:Density of the wastesAmount of intermediate and daily cover Amount of settlement that the waste will undergo following tippingThickness of cappingConstruction of lining and drainage layers.Protection of soil and water through:Installation of liner and collection systems.Storm water controlLeachate management.Landfill gas management.Nuisances and hazards management .CostsFeasibility studiesSite after care

Site investigations (costs involved may make small sites uneconomical).Site respect

n agriculture,windrow composting is the production of compost by pilingorganic matter or biodegradable waste, like animal manure and crop residues, inlong rows (windrows). This method is suited to producing large volumes of compost. These piles are generally turned to improve porosity and oxygencontent, mix in or remove moisture, and redistribute cooler and hotter portions of the pile. Windrow composting is the most commonly used of farm scalecomposting methods. Process control parameters include the initial ratios of carbon and nitrogen rich materials, the amount of bulking agents added to assureair porosity, the pile size, moisture content, and turning frequency.

sources and types of solid wastes

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