DESIGN OF AN EFFICIENT SOLID WASTE MANAGEMENT AND DISPOSAL SCHEDULING SYSTEM: A CASE STUDY OF ENUGU METROPOLIS

ABSTRACT

The Design of an Efficient Solid Waste Management and Disposal Scheduling System in a metropolis is hereby presented. The design employed ten landfill sites in contrast to the existing one landfill site in the metropolis. The metropolis was divided into ten zones and a Hungarian mathematical model was used to get the optimal assignment of the proposed landfill sites to the zones. This model was applied to the field data obtained from the road net-work of Enugu metropolis and Enugu State Waste Management Authority. The result gave a 52% decrease in the total disposal cost of solid waste presently generated.

APTER ONE

1.1   Introduction.

For many decades now, different research institutes of many countries, private organisations as well as individuals have been trying to develop or design an effective method of handling the solid wastes generated in their environment. This is because of the conspicuous effects of these wastes which have become a matter of great concern locally, nationally and even globally. The desire to control or handle these solid waste and its attendant problems led to the different waste management methods which exist today.

According to Agunwamba (2003), the problem of solid waste management in Nigeria has become more complex in recent times due to high rate of population growth, urbanisation, and industrialisation. He also stated that increased amount of different kinds of wastes are now being generated. Ajagbe (2004) stated that changes throughout the urban centres in the country over the years, particularly in demographic expansion have brought about phenomenal increase in the volume and diversity of solid waste generated daily in the country (Nigeria). The result of this is that heaps of refuse and garbage are common sight in our cities, urban areas, state capitals and even the Federal capital Territory. Dayo, K (2011) stated that in spite of the people’s expectations, observers note that Abuja, like other cities in the country, still grapples with waste management problems; as some areas, particularly the satellite towns stink because of the refuse heaps by the streets and walkways. It is clear from the above statement that most cities in Nigeria as well as Enugu metropolis are not free from the menace of solid wastes being generated everyday in the metropolis. Also in most Nigerian cities, waste management is being carried out in a disorderly manner (fire-brigade approach) which poses a serious health hazards to their citizens (Osuji, 1994). The reason could be that most of these cities have not embraced modern engineering based approach to waste management. In Enugu metropolis, the trend is also the same.

1.2  Solid Waste.

A good number of great authors have defined waste based on their own perspectives. Tchobanoglous et al (1977), defined waste as any unavoidable material resulting from domestic activities or industrial operation for which there is no economic demand and which must be disposed off. According to Odocha (1994), wastes are those materials which though may no longer be needed here, may become feedstock or raw material elsewhere. It implies that what is a waste to someone may be a raw material for another person. Wastes do not, therefore, altogether apply to worthless substances around us. He also defines waste as those materials which are generated as a result of normal operations over which we have control in terms of their production, disposal or discharge.    Ayaji, K (2008), stated that waste is anything that is no longer of use to the owner, which must be disposed off, of which the owner may not attach any economic value to it. Furthermore, Sridhar (1996), stated that waste is any unavoidable material resulting from domestic activities or industrial operations of which there is no economic demand and which must be disposed off.

Wastes are generally categorized into solid, liquid and gaseous wastes. Solid wastes generated in a city or district is usually called municipal solid wastes (MSW). These wastes can be categorized as follows: hazardous or non-hazardous, combustible or non-combustible, decomposable or non-decomposable, reusable or non-reusable wastes etc. Solid wastes (SW) disposal is the disposal or careful removal of solid or semi-solid materials resulting from human and animal activities that are useless, unwanted or hazardous. Solid wastes (SW) may be classified as follows:

Garbage: Degradeable wastes from food remains.

Rubbish: Non-decomposable wastes; combustible (such as paper, wood, clothes, plastics, rubber, leader etc) or non-combustible (such as metals, glass, stones,

ceramics, bottles etc).

Ashes: Residues of the combustion of solid fuels.

Large wastes: Demolition and construction debris or trees.

Dead animals: Remains of bodies of animals.

Sewage-treatment solids: Material retained on sewage-treatment screens, settled

Solids and biomass sludge.

Industrial wastes: Such as chemicals, paints and sand, computer parts, textile    materials.

Mining wastes: Slag heaps and coal refuse piles.

Agricultural wastes: Farm animals manure and crop materials.

1.2.1   Solid Waste Generation.

The rate at which solid wastes are been generated depends on a good number of factors which includes: the human population of the area under consideration, the living standards of the people, and their attitudes to waste prevention and control. According to Tehbanogolous, George, et al. (1977), solid waste products arise from our ways of life. Smart, N.U (2002), stated that when living standards rise, people consume more and waste increases. Cointreau- Levine, S (1999), in table 1.1 shows the waste generation (in kg/capital/day) of low-income, mid- income and high -income countries. The table 1.2 shows the solid waste generation rate of some cities/ countries of the world while table 1.3 shows the solid waste generation in Nigeria.

Table 1.1: Solid Waste Generation Rate of some Cities/ Countries.

	Waste generation rates (in kg/capital/day)
Low-income		Mid-income	High-income   Country
Country		country
Mixed urban	0.50-0.75	0.55-1.1	0.75-2.2
waste large city   (>500000)
Mixed urban	0.35-0.65	0.45-0.75	0.65-1.5
waste small to medium city (<500000)
Residential	0.25-0.45	0.35-0.65	0.55-1.0
waste only

Source: Cointreau-Levine, S. (1999).

Table1.2: Urban Waste Generation Rates.

S/N	City or country	Kg/person/day
i)	Industrialized countries
1	New Yoke city, USA	1.80
2	Hamburg ,Germany	0.85
3	Rome, Italy	0.69
ii)	Middle– income countries
4	Singapore	0.87
5	Hong Kong	0.85
6	Tunis, Tunisia	0.56
7	Medline, Colombia	0.54
8	Kano, Nigeria	0.46
9	Manila, Philippines	0.50
10	Cairo, Egypt	0.50
iii)	Low-income country
11	Jakarta, Indonesia	0.50
12	Surabaya, Indonesia	0.60
13	Bandung, Indonesia	0.52
14	Lahore, Pakistan	0.55
15	Karachi Pakistan	0.60
16	Calcutta, India	0.50
17	Kanpur, India	0.50

Source: Sandra (Outreach, 1982)

Table 1.3: Municipal Solid Waste Daily Generation in Nigeria.

S/N	State	Metric Tonne
1	Abia	2000
2	Adamawa	800
3	Anambra	2500
4	Akwa-ibom	700
5	Balyesa	600
6	Bauchi	900
7	Benue	800
8	Borno	900
9	Cross River	750
10	Delta	850
11	Ebonyi	600
12	Edo	900
13	Ekiti	800
14	Enugu	1000
15	Gombe	500
16	Imo	1000
17	Jigawa	600
18	Kaduna	1000
19	Kano	2000
20	Kastina	800
21	Kebbi	700
22	Kogi	500
23	Kwara	700
24	Lagos	6000
25	Nassarawa	400
26	Niger	700
26	Ogun	1000
28	Ondo	800
29	Osun	700
30	Oyo	1100
31	Plateau	700
32	Rivers	1500
33	Sokoto	900
34	Taraba	400
35	Yobe	400
36	Zamfara	400
37	FCT	3000

Source: Johnson, E (2006)

1.2.2   Solid Waste Composition.

The composition of solid waste generated from any given area depends on what the people throw away as waste. Uchegbu, S.N (2002), stated that in industrialized countries, packaging of goods contributes about thirty (30) per cent of the waste and fifty (50) per cent of the volume of household waste, food and yard scraps account for the remainder. Furthermore, he stated that in Nigeria, the average mass of waste disposed in big cities is

46kg/person/day.  Aliyu  Baba  Nabegu  (2011),  in  his  journal  (Solid  Waste  and  Its Implications for Climate Change in Nigeria) presented a table 1.4 of waste composition of some zones in Nigeria.

In Delhi- India, Dass Ravi (2007) stated that the solid waste generated in Delhi is approximately  6,000–6,500  MT  per  day  with  a  collection  efficiency  of  95%.  The composition of solid waste in Delhi is shown in Figure 1.1. The chemical characteristics of solid waste are as follows: moisture (43.65%), silt/inert (34%), organic carbon (20.47%), nitrogen (0.85%), potassium (0.69%), and phosphorus (0.34%) (Dass Ravi (2007)). Table

1.5 shows the general composition of waste in Malaysia.

Table 1.4: Percentage waste bulks collected in the three zones

zone waste	Nsukka	Lagos	Makurdi	Kano	Onitsha	Ibadan	Maiduguri
Putrescible	56	56	52.2	43.0	30.7	76	25.8
Plastic	8.4	4	8.2	4.0	9.2	4.0	18.1
Paper	13.8	14.0	12.3	17.0	23.1	6.6	7.5
Textile	3.1	–	2.5	7.0	6.2	1.4	3.9
Metal	6.8	4.0	7.1	5.0	6.2	2.5	9.1
Glass	2.5	3.0	3.6	2.0	9.2	0.6	4.3
others	9.4	19.0	14.0	22.0	15.4	8.9	31.3

Source: Aliyu Baba Nabegu (2011),

Table 1.5: General Composition of Waste in Malaysia.

Materials	% by Weight
Organic	47.0
Paper	15.0
Plastics	14.0
Wood, garden waste	4.0
Metal	4.0
Glass	3.0
Textile	3.0
Other	10.0

Figure 1.1: Composition of Solid Waste of Delhi-India. Source: Dass Ravi (2007)

1.3    The impact of solid wastes in human society.

The impact of solid wastes in human society cannot be over-emphasized. Land, water and air pollutions are all because of the accumulation of solid wastes, which also open doors for disease spread, with consequent suffering and hardship, stunted economic development and diminished productivity. Anupam Khajuria et al (2010) stated that in developing Asian countries, the municipal co-operations are unable to handle the increasing amount of municipal solid waste, which has led to the uncollected waste being spread on roads and in other public areas leading to tremendous pollution and destruction of land and negative impact on human health.  Uchegbu (2002), in his research work stated that “Cholera out- breaks or spread in most part of Nigeria had been as a result of accumulation of solid wastes in our society”. According to him, the life expectancy in developing countries is fifty-three (53) years while that of developed countries is seventy- five (75) years and the reason is that waste management is still very poor in our society when compared to that of developed countries. Most drainage gutters are being blocked with solid wastes; as a result flood now destroys many of our tarred roads, residential houses, farmlands, hospitals, schools etc. From observation, most streams in our society are no longer drinkable because of the poisonous liquid from solid wastes that filters into it.   Dayo (2011), in his article stated that water sources near such waste dumps easily become contaminated and a consequence, explains Dr Ibrahim Idris, an expert in community health, is the spread of gastro-intestinal and parasitic diseases.  The awful odour that comes out of these wastes is irritating to the members of the society.  In  spite  of all  these  problems  associated with solid  wastes  in  our  society,  an appropriate waste  management system if  applied can  handle these problems and  make human environment decent and enjoyable.

1.4   Brief history of was te manage ment in Enugu Metropolis.

Enugu metropolis in Enugu state was used as a case study in this research work because of the solid waste management problems it suffered in the last regime of the state. In 2006, Enugu was regarded as one of the dirtiest cities with over one thousand (1000) metric tonne of waste generated daily (Ezeanyanwu, 2006). Heaps of refuse were like mountains along the roads and streets exposing the environment to severe pollution.

Enugu metropolis is made up of three local government areas namely: Enugu North (State Headquarters), Enugu East and Enugu South. The metropolis occupies an important socio-economic position in Enugu state and Eastern zone of Nigeria. The human population of the metropolis during 2006 census was seven Hundred and twenty-two thousand, six Hundred and sixty-four (722,664). Figure1.2 below shows the  road net-work of Enugu metropolis.

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