LITERATURE REVIEW
This chapter deals with review of related literature on solid waste management. The literature is reviewed under concept of solid waste, human perception of solid waste, types and sources of solid waste management practices including waste minimization, resource recovery and disposal techniques.
2.2 CONCEPT OF SOLID WASTE
Attewell (1993:5) defined solid waste as mans stream or rise in the air. They are the non liquid, non gaseous residues of our manufacturing, construction, cooking, recreation, agricultural and other activities that are used and then discard materials, included in these category are out dated newspapers, glass, bottles, metal, cans, paper cups, plastic, abandoned automobiles, demolition rubble, mine tailing, dead animals, dewatering sewage sludge and the garbage from kitchen (Mantel 1975:11).
However waste generally refers to any substance which constitutes a scrap material and, or other unisanted sulphur substances arising from the application of any process, and or any substance or article that required to be disposed off as being broken or contaminated but does not include explosive substance within meaning of the Explosive Act 1875.
When something seized to be a useful object it becomes a waste. Waste is therefore a relative term whose meaning depends on what we use and how we use it. Remain food particles from dinner may be cast into garbage or into a garbage container as waste but under another circumstance the bone may be preserved fore soup and presented to an appreciative dog. (Sewell 1988:219).
Sewell (1988:219) further argued that one may use a piece of paper for not then deposit it into a waste basket as trash but later when lacking a convenient scrap out of the waste basket and use the reserve side thus transforming that paper back into a useful object. It therefore implies that the kind and quantity of solid waste today are largely determined by cultural institution (WHO 1989:1). These solid wastes when not properly managed are of grave consequences to the environment. They pose problems such as:
Public healthy hazards
Aesthetic degradation
Occupation of space
Water and air pollution.
Based on the above problems inherited in solid waste generation and mismanagement, Houghton (1993:1) prescribed four stage decision procedure for effective waste management namely:
Avoid creating waste where possible.
Recycling unavoidable waste where possible.
If recycling for materials used is not possible recover energy from them.
Where the above options have been exhausted utilize the best practicable environmental option to dispose of the waste. WHO (1989:1) maintained that solid waste inadequately collected and disposed causes usual degradation of residual area and block drainage channels. Sewell (1988:222) agreed that solid waste constitute a visible and durable blight upon our land scrap. Therefore, broken parts of automobile litter streets and fields, trash and garbage spread along high ways, open dumps often located on the high ways and residential areas generate odour and constitute eye fore to the inhabitant WHO (1987:1) stressed that if garbage litter the street, the opposition group are likely to use that as a political tool against the opponents.
In spite of the above, the periphery of our urban centres are bedeviled with environmental degradation and aesthetic deformation are still evident, for instance, mine waste like coal reduce aesthetic beauty of the area (Sewell 1988:223).
2.3 SOURCES AND TYPES OF SOLID WASTE
From the definition of solid waste. It was observed that solid waste all non-gaseous, liquid residues of our manufacture and other activities (Attwewell 1993:5). It is on this basis that (Sewell 1988:288) classified the basic sources of solid waste as Residential Commercial and municipal, industrial, open area, Treatment Plants and Agricultural. The use and activities of people living in these areas to a large extent affect also the type of waste we can expect to find in each of them, although a particular type of waste could be found in move than one of the sources. For instance we can find food wastes in residential, commercial, municipal and industrial sources of solid waste. The special wastes can also be found in the residential, commercial, municipal and open areas as their sources.
Possession as continuing economic resources, Sewell (1988:220) observed that cans be salvaged and used as containers, while papers can be used, reused and eventually burnt for heat generation. In view of the above (Hardoy 1982:136) emphasized that a greater recognition of the need to develop local solution which match local needs and possibilities should be emphasized because the condition varies so much from city to city in the scale and type of refuse generation as well as local possibilities for recycling.
2.4 WASTE MINIMIZATION AND TREATMENT INCINERATION
For certain types of wastes and for large scale waste disposal, incineration which is the burning of waste in specially constructed chamber, (incineration or combustion chamber)provides one of the simplest and most effective means of disposing of domestic refuse or waste.
Incineration was extensively used in Nigeria during the colonial days for the disposal of domestic wastes. Today the use of incineration is virtually extinct in many parts of Nigeria. Yet incineration is not only simple and efficient, it is capable of adoption for use in variety of situations and size with the possibility of the equipment being made locally to reduce cost. Thus it was the initial high cost of incinerations that discouraged its wide spread application in Nigeria added to the fact that the economics of incineration require large plants that are efficiently operated.
However for incineration plant to be very effective it must be located with great care since its advantages include being extremely, hygienic eliminating many of the problems of tipping such as wind blown refuse strench, rodents flies and other pests. Incineration is the inevitable answer.
2.5 SOLID WASTE MANAGEMENT PRACTICES
Authorities involved in solid waste management solid waste management is as old as human congregation in communities (Mantel 1977:71), but the migrant component or our cities ands the novelty of the urban culture in many of them have created a state of Omuta (1988:78 88) observed that the unprecedented increase in urban population result from the neglect of rural area which created high save of rural urban migration. Such increase, he stressed led to increase in the physical size of the cities and the rate of solid waste generation. In this regard Sada (1988:79), maintain that cities are now regarded as a geographic no mans land where the maintenance of the environment becomes no mans business. In Nigeria, he stressed that two broad systems of solid waste management include public and private responsibility, the former being more conventional. In this case, the solid waste disposal unit is established at the local council level as an operational section of the health Department (Sada 1988:80). In support of the above arrangement Hardoy and Mithin (1992:136) maintained that local based organisations and government are responsible for municipal solid waste management.
In this regard, solid waste management is backed up with laws to ensure its proper execution, since solid waste management is an environmental issue. In Nigeria, Etomi (1990:36) stated that real environmental regulation in Nigeria is the response of National Emergency. That is why the Federal Environmental Protection Agency (FEPA) Decree of 1988, which Created State and Local Agencies in Nigeria, empowered the agencies to ensure healthy environment through proper solid waste management (FEPA 1988, No 58). To maximize public involvement in solid waste management, Sada (1988:84) maintain that community leaders must be fully integrated into the solid waste management policy making process, stressing that traditional rulers should liaise with the grassroots primary generator of solid wastes and urban authorities.
However, instability in government adversely affect the management processes of solid wastes. This is true because, the frequent change in the institutional framework, by the government in power, for solid waste management or the chief executive denies the waste management organisation the benefit of accumulated experience that is very essential in the operation of such institutions. In the same vein, Okpala (1986:68) emphasized that such instabilities contribute substantially to the containing ineffectiveness of solid waste management. He, however, suggested that waste management should be solely, responsibility local government authority in order to give the local government greater autonomy; a single purpose waste management agency for each urban centre to handle all refuse collection and disposal within its area of jurisdiction be created, private contractors with the responsibility of collecting refuse from residence of generators be established. The last option is very important because in many developed countries waste management has from government responsibility to private individuals and companies. This saves the government local or state from huge expenses that could have been involved in this venture.
2.6 RESOURCE RECOVERY
Resource recovery according to Sewell (1988:243) is the retrieval of material from waste stream for some economically useful function. He stressed that the term can refer to the complicated sorting of papers, cans, bottles and other materials from domestic wastes, and subsequent processing unit steel furnace Hester and Harrison (1994:2) David 1981:17) remarked that recovery could be for an equivalent use such as the reprocessing of newsprint (paper recycling), or for a degraded use such as t he recovery of heat or compost from domestic waste.
A brief survey of materials which are collected from municipal pack truck . Refuse depot vary in size, shape and physical characteristics and such heterogeneous material pose considerable difficulties in processing for resource recovery operation (Pavoni 1975:205). He stressed that heterogeneous nature of municipal solid waste materials render some portion that could be retrieved useless since salvaging such waste materials require extract expenditure of money, power and labour in subsequent sorting and separation operation if urban managers are to be able to cope with increased waste now and in the future.
Howbeit, incineration should be located in an industrial district and as close as possible to the centre of population to be served so that collection cost may be reduced to minimum. Also efficient, highly trained and dedicated personnel are necessary to maximize it use. Again, incineration is made3 up of two main methods open and controlled incineration. As a principal for the construction of incineration. As a principal for the construction of incinerator Berfy and Horton (1974) suggested free supply of air, provision fro conservation of heat and provision for effective stocking as necessity for better burning.
It should be such that would burn the daily generated wastes without undue delay. The temperature should be high enough to burn all the combustible starting with the drier portion of the solid wastes.
COMPOSTING
As it is common with all forms of waste disposal, it is one of the good ways by which refuse or waste is converted into humus, organic product that is used as an agricultural fertilizer to improve and sustain good and health growth of agricultural crops as a waste disposal attempt composting reduces the bulk of refuse to about 40 60%. Although in Nigeria any composting that occurs is accidental rather then a conscious effort to utilize the material for agriculture, it has very attractive advantages which include:
It kills diseases because of heat
It is most suitable for organic refuse
It is more naturally assimilated by land
It does not produce air or water pollution.
2.7 DISPOSAL TECHNIQUES
According to Berry and Horton, (1974), in recent years the character refuse has changed because f the new techniques in food packing in home heating and in disposal itself. Notably the advent of the household garbage grinder. The significant effect of these new techniques has been to change the composition of refuse, reducing the proportion of wet garbage and ash and increasing the relative amount of paper for this report six methods that could be used to dispose refuse would be reviewed.
Swine feeding of the garbage portion.
Open dumping (which accounted for 77 percent of all collected solid waste).
Sanitary land fill.
Incineration (Accounts for 10% of domestic solid waste).
Compositing.
The feeding of garbage to swine was at one time a very profitable method of refuse disposal in the united state but not until the outbreaks of vascular exanthema among farm animals that resulted to a substantial economic losses Berry and Horton (1974). There are generally tow types of swine feeding operation: large and small scavengers. (The major obstacles is cooking the refuse and separating the garbage from the inedible materials.
Acording to chanleth (1979:192) from history people have continually struggled to manage their natural environments in order to improve their health and well-being. This method is the simplest method of disposal although it is also the least satisfactory usually open dump is an area where refuse is disposed and allowed to remain exposed tot he atmosphere. The danger of this method is that the dumps form a breeding ground for mosquitoes, rats and encourage the epizortics of fungal and bacterial diseases. Also the outbreak of fire at some dumps created an air pollution problem. Added to this some dumps become swampy and water filled where this occurs the probability of ground water contamination is high. Communicatively both burning refuse and stagnant water causes serious odour and health problems. In every way, the open is both undesirable and an unnecessary hazard to public health. In deed the open dump is a relic of a paste era and cannot be considered unacceptable method of refuse disposal.
SANITARY LANDFILL
A substantial retirement of open dump method. It has the advantage over the open dump method in that:
It does not create a nuisance.
It does not produce odour.
It does not produce air or water pollution.
Infact, an efficient sanitary land fill operation will inhibit flies, mosquitoes and rats will seal in odours; prevent water in filtration and will minimize blowing and scattering. Infact, scholars of urban planning see this method of refuse disposal as a method whereby a community disposal problem may be solved in an economic manner and also provide opportunities to create improved sites and to shape the landscape.
In practice a sanitary landfill operation may involve the preparation of site by digging trenches or cutting into slope with earth moving machinery. The refuse is dumped into the cavities and is covered with a layer of earth taken from either the trench or the slope. Trees can be planted on it.