Definition of Solid Waste
Solid wastes are the organic and inorganic waste materials such as product packaging, grass clippings, furniture, clothing, bottles, kitchen refuse, paper, appliances, paint cans, batteries, etc. These wastes are produced in our society and generally do not carry any value to its first user.
Classification of Solid Waste
Solid wastes are classified according to their sources ant their types.
Classification of Solid Waste According to Sources
Commercial : This refers to solid waste containing of leftover food, glasses, metals, ashes, etc, generated from stores, restaurants, markets, hotels, auto-repair shops, medical facilities, etc.
Residential : It includes solid waste from dwellings, apartments, etc… and it consist leftover such as food, fruit and vegetable peels, plastic, clothes, ashes, etc.
Municipal : This solid waste includes dust, leafy matter, building debris, treatment plant residual sludge, etc, which is generated from various municipal activities such as construction and demolition, street cleaning, landscaping, etc.
Institutional : This type of solid waste mainly consist of paper, plastic, glasses, etc, which is generated from educational, administrative and public buildings such as schools, colleges, offices, etc.
Open Areas : This solid waste includes waste from areas such as streets, alleys, parks, vacant lots, playgrounds, beaches, highways, recreational areas, etc.
Industrial : Solid waste mainly includes process wastes, ashes, demolition and construction wastes, etc, due to ongoing industrial activities.
Agricultural : Solid waste mainly consist of spoiled food grains and vegetables, agricultural remains, litter, etc, generated from fields, orchards, vineyards, farms, etc. etc
Classification of Solid Waste According to Types
Ashes and Residues : These are the substances remaining from the burning of wood, coal, charcoal and other combustible materials used for cooking and heating in the houses, institutes and small industrial establishments. When produced in large quantities, as in power generation plants and factories, these are classified as Industrial wastes. Ashes consist of fine powdery residue, cinders and clinker often mixed with small pieces of metal and glass. Since ashes and residues are almost entirely inorganic they are valuable in landfills.
Street Wastes : These refers to solid waste that are collected from streets, walkways, parks and vacant plots which consist of paper, cardboard, plastic, leaves, and other vegetable matter. Littering in public places is indeed a widespread and acute problem in many countries. solid waste management must address this menace appropriately.
Garbage : This refers to animal and vegetable wastes resulting from the handling, sale, storage, preparation, cooking and serving of food. Garbage comprising these wastes contains rotting organic matter, which produces an obnoxious smell and attracts rats and other vermin. Therefore special attention is required in storage, handling and disposal of this type of solid waste.
Bulky Wastes : These includes large household appliances such as refrigerators, washing machines, furniture, crates, vehicle parts, tyres, wood, trees and branches. Since these household wastes cannot be accommodated in normal storage containers, they require a special collection mechanism.
Biodegradable and Non-Biodegradable Wastes : Biodegradable wastes mainly refer to substances consisting of organic matter such as leftover food, vegetable and fruit peels, paper, textile, wood, etc, which is generated from various household and industrial activities. Because of the action of micro-organisms, these wastes are degraded from complex to simpler compounds. Non-Biodegradable wastes consist of inorganic and recyclable materials such as plastic, glass, cans, metals, etc. Below is the table showing comparison between biodegradable and non-biodegradable wastes with their degeneration time.( time required to break from complex to simple biological form ).
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Combustible and Non-Combustible Wastes : These consist of waste generated from households, institutions, commercial activities, excluding food wastes and other highly rotting materials. Typically, while combustible materials consist of paper, cardboard, textile, rubber, garden trimmings, etc. Non-combustible materials consist items such as glass, crockery, tin, aluminium cans, ferrous and non-ferrous materials and dirt.
Abandoned Vehicles : This includes automobiles, trucks and trailers that are abandoned on streets and other public places. However, abandoned vehicles have significant scrap value for metal and their value to collectors is highly variable.
Dead Animals : With regard to municipal wastes, dead animals are those that die naturally or are accidentally killed on road. Note that this category does not include carcasses and animal parts from slaughter-houses, which are regarded as industrial wastes. Dead animals are divided into two groups – large and small. Among the large animals are horses, cows, goats, sheep, pigs etc. Small animals include dogs, cats, rats, etc. The reason for this differentiation is that large animals require special equipment for lifting and handling when they are removed. If not collected promptly, dead animals pose a threat to public health since they attract flies and other vermin as they decay. Their presence in public places is particularly offensive from the aesthetic point of view as well.
Farm Wastes : These wastes result from diverse agricultural activities such as planting, harvesting, production of milk, rearing of animals for slaughter and the operation of feedlots. In many areas, the disposal of animal waste has become a critical problem, especially from feedlots, poultry farms and dairies.
Hazardous Wastes : These solid wastes are defined as wastes of industrial, institutional or consumer origin that are potentially dangerous either immediately or over a period of time to human beings and the environment. This is due to their physical, chemical and biological or radioactive characteristics like ignitability, corrosivity, reactivity and toxicity. Note that in some cases the active agents may be liquid or gaseous hazardous wastes. These are, nevertheless classified as solid wastes and they are confined in solid containers.
Typical examples of hazardous wastes are empty containers of solvents, paints and pesticides. Certain hazardous wastes may cause explosions in incinerators and fires at landfill sites. Others such as pathological wastes from hospitals and radioactive wastes also require special handling. Effective management practices should ensure that hazardous wastes are stored, collected, transported and disposed of separately, preferably after suitable treatment to render them harmless.
Sewage Wastes : The solid by-products of sewage treatment are classified as sewage wastes. They are mostly organic and derived from the treatment of organic sludge separated from both raw and treated sewage. The inorganic fraction of raw sewage such as grit and eggshells is separated at the preliminary stage of treatment. This is done so that it may entrain putrescible organic matter with pathogens and must be buried without delay. The bulk of treated, dewatered sludge is useful as as soil conditioner but is invariably uneconomical. Solid sludge, therefore enters the stream of municipal wastes, unless special arrangements are made for its disposal.