Project Abstract

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

Project Overview

<p> 1.1 Introduction.<br>For many decades now, different research institutes of many countries, private<br>organisations as well as individuals have been trying to develop or design an effective<br>method of handling the solid wastes generated in their environment. This is because of<br>the conspicuous effects of these wastes which have become a matter of great concern<br>locally, nationally and even globally. The desire to control or handle these solid waste<br>and its attendant problems led to the different waste management methods which exist<br>today.<br>According to Agunwamba (2003), the problem of solid waste management in Nigeria<br>has become more complex in recent times due to high rate of population growth,<br>urbanisation, and industrialisation. He also stated that increased amount of different<br>kinds of wastes are now being generated. Ajagbe (2004) stated that changes throughout<br>the urban centres in the country over the years, particularly in demographic expansion<br>have brought about phenomenal increase in the volume and diversity of solid waste<br>generated daily in the country (Nigeria). The result of this is that heaps of refuse and<br>garbage are common sight in our cities, urban areas, state capitals and even the Federal<br>capital Territory. Dayo, K (2011) stated that in spite of the people’s expectations,<br>observers note that Abuja, like other cities in the country, still grapples with waste<br>management problems; as some areas, particularly the satellite towns stink because of<br>the refuse heaps by the streets and walkways. It is clear from the above statement that<br>most cities in Nigeria as well as Enugu metropolis are not free from the menace of solid<br>wastes being generated everyday in the metropolis. Also in most Nigerian cities, waste<br>management is being carried out in a disorderly manner (fire-brigade approach) which<br>poses a serious health hazards to their citizens (Osuji, 1994). The reason could be that<br>most of these cities have not embraced modern engineering based approach to waste<br>management. In Enugu metropolis, the trend is also the same.<br>2<br>1.2 Solid Waste.<br>A good number of great authors have defined waste based on their own perspectives.<br>Tchobanoglous et al (1977), defined waste as any unavoidable material resulting from<br>domestic activities or industrial operation for which there is no economic demand and<br>which must be disposed off. According to Odocha (1994), wastes are those materials which<br>though may no longer be needed here, may become feedstock or raw material elsewhere. It<br>implies that what is a waste to someone may be a raw material for another person. Wastes<br>do not, therefore, altogether apply to worthless substances around us. He also defines waste<br>as those materials which are generated as a result of normal operations over which we have<br>control in terms of their production, disposal or discharge. Ayaji, K (2008), stated that<br>waste is anything that is no longer of use to the owner, which must be disposed off, of<br>which the owner may not attach any economic value to it. Furthermore, Sridhar (1996),<br>stated that waste is any unavoidable material resulting from domestic activities or industrial<br>operations of which there is no economic demand and which must be disposed off.<br>Wastes are generally categorized into solid, liquid and gaseous wastes. Solid wastes<br>generated in a city or district is usually called municipal solid wastes (MSW). These wastes<br>can be categorized as follows: hazardous or non-hazardous, combustible or non-combustible,<br>decomposable or non-decomposable, reusable or non-reusable wastes etc. Solid wastes (SW)<br>disposal is the disposal or careful removal of solid or semi-solid materials resulting from<br>human and animal activities that are useless, unwanted or hazardous. Solid wastes (SW) may<br>be classified as follows:<br>Garbage: Degradeable wastes from food remains.<br>Rubbish: Non-decomposable wastes; combustible (such as paper, wood, clothes, plastics,<br>rubber, leader etc) or non-combustible (such as metals, glass, stones,<br>ceramics, bottles etc).<br>Ashes: Residues of the combustion of solid fuels.<br>Large wastes: Demolition and construction debris or trees.<br>Dead animals: Remains of bodies of animals.<br>Sewage-treatment solids: Material retained on sewage-treatment screens, settled<br>Solids and biomass sludge.<br>3<br>Industrial wastes: Such as chemicals, paints and sand, computer parts, textile materials.<br>Mining wastes: Slag heaps and coal refuse piles.<br>Agricultural wastes: Farm animals manure and crop materials.<br>1.2.1 Solid Waste Generation.<br>The rate at which solid wastes are been generated depends on a good number of factors<br>which includes: the human population of the area under consideration, the living standards of<br>the people, and their attitudes to waste prevention and control. According to Tehbanogolous,<br>George, et al. (1977), solid waste products arise from our ways of life. Smart, N.U (2002),<br>stated that when living standards rise, people consume more and waste increases. Cointreau-<br>Levine, S (1999), in table 1.1 shows the waste generation (in kg/capital/day) of low-income,<br>mid- income and high -income countries. The table 1.2 shows the solid waste generation rate<br>of some cities/ countries of the world while table 1.3 shows the solid waste generation in<br>Nigeria.<br>Table 1.1: Solid Waste Generation Rate of some Cities/ Countries.<br>Source: Cointreau-Levine, S. (1999).<br>Waste generation rates (in kg/capital/day)<br>Low-income<br>Country<br>Mid-income<br>country<br>High-income<br>Country<br>Mixed urban<br>waste large city<br>(&gt;500000)<br>0.50-0.75 0.55-1.1 0.75-2.2<br>Mixed urban<br>waste small to<br>medium city<br>(&lt;500000)<br>0.35-0.65 0.45-0.75 0.65-1.5<br>Residential<br>waste only<br>0.25-0.45 0.35-0.65 0.55-1.0<br>4<br>Table1.2: Urban Waste Generation Rates.<br>Source: Sandra (Outreach, 1982)<br>S/N City or country Kg/person/day<br>i) Industrialized countries<br>1 New Yoke city, USA 1.80<br>2 Hamburg ,Germany 0.85<br>3 Rome, Italy 0.69<br>ii) Middle- income countries<br>4 Singapore 0.87<br>5 Hong Kong 0.85<br>6 Tunis, Tunisia 0.56<br>7 Medline, Colombia 0.54<br>8 Kano, Nigeria 0.46<br>9 Manila, Philippines 0.50<br>10 Cairo, Egypt 0.50<br>iii) Low-income country<br>11 Jakarta, Indonesia 0.50<br>12 Surabaya, Indonesia 0.60<br>13 Bandung, Indonesia 0.52<br>14 Lahore, Pakistan 0.55<br>15 Karachi Pakistan 0.60<br>16 Calcutta, India 0.50<br>17 Kanpur, India 0.50<br>5<br>Table 1.3: Municipal Solid Waste Daily Generation in Nigeria.<br>Source: Johnson, E (2006)<br>S/N State Metric Tonne<br>1 Abia 2000<br>2 Adamawa 800<br>3 Anambra 2500<br>4 Akwa-ibom 700<br>5 Balyesa 600<br>6 Bauchi 900<br>7 Benue 800<br>8 Borno 900<br>9 Cross River 750<br>10 Delta 850<br>11 Ebonyi 600<br>12 Edo 900<br>13 Ekiti 800<br>14 Enugu 1000<br>15 Gombe 500<br>16 Imo 1000<br>17 Jigawa 600<br>18 Kaduna 1000<br>19 Kano 2000<br>20 Kastina 800<br>21 Kebbi 700<br>22 Kogi 500<br>23 Kwara 700<br>24 Lagos 6000<br>25 Nassarawa 400<br>26 Niger 700<br>26 Ogun 1000<br>28 Ondo 800<br>29 Osun 700<br>30 Oyo 1100<br>31 Plateau 700<br>32 Rivers 1500<br>33 Sokoto 900<br>34 Taraba 400<br>35 Yobe 400<br>36 Zamfara 400<br>37 FCT 3000<br>6<br>1.2.2 Solid Waste Composition.<br>The composition of solid waste generated from any given area depends on what the<br>people throw away as waste. Uchegbu, S.N (2002), stated that in industrialized countries,<br>packaging of goods contributes about thirty (30) per cent of the waste and fifty (50) per cent<br>of the volume of household waste, food and yard scraps account for the remainder.<br>Furthermore, he stated that in Nigeria, the average mass of waste disposed in big cities is<br>46kg/person/day. Aliyu Baba Nabegu (2011), in his journal (Solid Waste and Its<br>Implications for Climate Change in Nigeria) presented a table 1.4 of waste composition of<br>some zones in Nigeria.<br>In Delhi- India, Dass Ravi (2007) stated that the solid waste generated in Delhi is<br>approximately 6,000–6,500 MT per day with a collection efficiency of 95%. The<br>composition of solid waste in Delhi is shown in Figure 1.1. The chemical characteristics of<br>solid waste are as follows: moisture (43.65%), silt/inert (34%), organic carbon (20.47%),<br>nitrogen (0.85%), potassium (0.69%), and phosphorus (0.34%) (Dass Ravi (2007)). Table<br>1.5 shows the general composition of waste in Malaysia.<br>Table 1.4: Percentage waste bulks collected in the three zones<br>Source: Aliyu Baba Nabegu (2011),<br>zone<br>waste<br>Nsukka Lagos Makurdi Kano Onitsha Ibadan Maiduguri<br>Putrescible<br>56 5 6 52.2 43.0 30.7 76 25.8<br>Plastic<br>8.4 4 8.2 4.0 9.2 4.0 18.1<br>Paper<br>13.8 14.0 12.3 17.0 23.1 6.6 7.5<br>Textile<br>3.1 – 2.5 7.0 6.2 1.4 3.9<br>Metal<br>6.8 4.0 7.1 5.0 6.2 2.5 9.1<br>Glass<br>2.5 3.0 3.6 2.0 9.2 0.6 4.3<br>others<br>9.4 19.0 14.0 22.0 15.4 8.9 31.3<br>7<br>Table 1.5: General Composition of Waste in Malaysia.<br>Materials % by Weight<br>Organic 47.0<br>Paper<br>15.0<br>Plastics<br>14.0<br>Wood, garden waste<br>4.0<br>Metal<br>4.0<br>Glass 3.0<br>Textile 3.0<br>Other 10.0<br>Source: Huszain Huzin (2004).<br>Figure 1.1: Composition of Solid Waste of Delhi-India.<br>Source: Dass Ravi (2007)<br>8<br>1.3 The impact of solid wastes in human society.<br>The impact of solid wastes in human society cannot be over-emphasized. Land, water and air<br>pollutions are all because of the accumulation of solid wastes, which also open doors for<br>disease spread, with consequent suffering and hardship, stunted economic development and<br>diminished productivity. Anupam Khajuria et al (2010) stated that in developing Asian<br>countries, the municipal co-operations are unable to handle the increasing amount of<br>municipal solid waste, which has led to the uncollected waste being spread on roads and in<br>other public areas leading to tremendous pollution and destruction of land and negative<br>impact on human health. Uchegbu (2002), in his research work stated that “Cholera outbreaks<br>or spread in most part of Nigeria had been as a result of accumulation of solid wastes<br>in our society”. According to him, the life expectancy in developing countries is fifty-three<br>(53) years while that of developed countries is seventy- five (75) years and the reason is that<br>waste management is still very poor in our society when compared to that of developed<br>countries. Most drainage gutters are being blocked with solid wastes; as a result flood now<br>destroys many of our tarred roads, residential houses, farmlands, hospitals, schools etc. From<br>observation, most streams in our society are no longer drinkable because of the poisonous<br>liquid from solid wastes that filters into it. Dayo (2011), in his article stated that water<br>sources near such waste dumps easily become contaminated and a consequence, explains Dr<br>Ibrahim Idris, an expert in community health, is the spread of gastro-intestinal and parasitic<br>diseases. The awful odour that comes out of these wastes is irritating to the members of the<br>society. In spite of all these problems associated with solid wastes in our society, an<br>appropriate waste management system if applied can handle these problems and make<br>human environment decent and enjoyable.<br>9<br>1.4 Brief history of waste management in Enugu Metropolis.<br>Enugu metropolis in Enugu state was used as a case study in this research work because<br>of the solid waste management problems it suffered in the last regime of the state. In 2006,<br>Enugu was regarded as one of the dirtiest cities with over one thousand (1000) metric tonne<br>of waste generated daily (Ezeanyanwu, 2006). Heaps of refuse were like mountains along the<br>roads and streets exposing the environment to severe pollution.<br>Enugu metropolis is made up of three local government areas namely: Enugu North<br>(State Headquarters), Enugu East and Enugu South. The metropolis occupies an important<br>socio-economic position in Enugu state and Eastern zone of Nigeria. The human population<br>of the metropolis during 2006 census was seven Hundred and twenty-two thousand, six<br>Hundred and sixty-four (722,664). Figure1.2 below shows the road net-work of Enugu<br>metropolis.<br>Figure 1.2: Road Net-Work of Enugu Metropolis.<br>Source: Map data Europa Technologies (2009).<br>10<br>According to Frank Egwu (2008), the history of waste management in Enugu and<br>Nigeria at large can be traced by the Local Government administration on sanitation. Before<br>creation of the taskforce in charge of sanitation, Local Government Areas were responsible<br>for environmental cleanliness as entrenched in 1979 constitution of Nigeria. This continued<br>until 1985 when the waste management leadership of Enugu changed baton. The then<br>military governor of Anambra State, Navy Captain Monday Ikpeazu launched a taskforce on<br>environmental cleanliness as a complementary to the decree of War Against Indiscipline<br>(WAI) by Major General Buhari through Lt. Ideagbo, the then officer in charge of WAI. The<br>people reacted negatively to the WAI because of the forceful and brutal nature of the<br>military. This was a problem and solid waste management in the metropolis was still very<br>poor. In 1985, the Anambra State Environmental Sanitation Agency (ASESA) was<br>established by Edit No: 15 of 1985 and their activities were enhanced by the introduction of<br>the World Bank Project in 1985 (Agunwamba, 2003). They were responsible for the<br>collection and disposal of solid waste generated in Enugu metropolis using container trucks,<br>tippers, side loaders and rear loading compaction trucks used for collection of wastes from<br>bins placed at different positions, municipal containers and built-up dumps placed at<br>strategic positions. Disposal of the solid waste was mainly at a sanitary landfill or controlled<br>landfill site.<br>ASESA used the method of built-up temporary dumps which gave rise to indiscriminate<br>dumping of wastes, environmental pollution and spread of diseases in the metropolis.<br>ASESA also used a more civilized approach in their management which empowered the<br>citizens to participate in the maintenance and cleaning of the environment. ASESA<br>continued to be in charge of environmental sanitation in the metropolis until 1991 when<br>Enugu State was created (Egwu, 2008). Assets and liabilities of ASESA were shared among<br>Enugu and Anambra State. This affected the number of available solid waste management<br>equipment for Enugu metropolis. The World Bank Assisted Project (WBAP) on sanitation<br>based at Onitsha then, collected all their waste management equipment and this helped to<br>compound waste management problem in Enugu metropolis.<br>As a result of this lack of equipment, Enugu state established a new agency (ENSEPA)<br>that will be responsible for managing all the environmental problems including collection<br>and disposal of solid wastes generated in the state. Enugu State Environmental Protection<br>11<br>Agency (ENSEPA) procured new equipment which includes three compactors and some<br>cubic-containers, but these were not sufficient for handling the volumes of wastes generated.<br>As a result of this, the agency divided Enugu into zones and officers were recruited to man<br>each zone. The agency made use of built-up refuse dumps or temporary transfer stations<br>where wastes were gathered for a certain period of time and then, transferred to the sanitary<br>landfill. ENSEPA also made use of managing director cum chief executive officer unlike<br>ASESA that used general manager, and this actually gave boost to waste management in<br>Enugu state as a whole. Enugu continued to suffer the lack of waste disposal equipment.<br>In 2004, there was a noticeable problem of waste management in the country, so, the<br>federal government created the Ministry of Environment and Mineral Resources (Egwu,<br>Frank (2008). This ministry will be in charge of managing environmental problems which<br>include: land pollution, land degradation, erosion control, deforestation etc, while other<br>environmental protection agencies will take care of solid and liquid wastes problems of the<br>environment. It was at this period that Enugu State Waste Management Authority<br>(ESWAMA), an off-shoot of ENSEPA, which now manages both solid and liquid wastes<br>generated in Enugu state, was established.<br>ESWAMA was established in 2004 through Decree number 8 of 2004 constitution and<br>was officially launched on 25th January, 2005 (Ayaji, 2008). This agency inherited both the<br>assets and the liabilities of ENSEPA, but since then, a lot of innovations had been put in<br>place to improve solid waste management in the state. ESWAMA started its innovation<br>activities by first of all re-organizing its organizational structure as shown in figure 1.3. New<br>offices were created and more staffs were recruited to man these offices. The agency also<br>divided Enugu metropolis into ten (10) zones: (1) Abakpa, (2) GRA, (3) Trans-Ekulu, (4)<br>New Haven/ Emene, (5) New Layout, (6) Ogui/Asata, (7) Coal Camp/Agbani Road, (8) Idaw<br>River/Garriki, (9) Achara Layout, (10) Independence Layout zone (see figure 1.4 below).<br>The operation bag your waste and Private Sector Participation (PSPs) were introduced.<br>Bagging of waste was introduced because it is portable, hygienic, reduces litter and stops<br>odour spread. The PSPs collect wastes from streets and zones assigned to them, sensitize the<br>people in the area and collect revenue from the people residing in the area, street or zones.<br>The PSPs no longer collect fees or revenues from the people because of some<br>misappropriation of revenues collected. ESWAMA revenue unit handles this exclusively.<br>12<br>The ESWAMA also procured one thousand (1000) waste collection buckets or dumpsters;<br>nine hundred and thirty (930) of it was given to Enugu metropolis, while seventy (70) of it<br>was distributed to other parts of the state. Fourteen compactors were procured, and one of<br>them is being used at Nsukka Local Government Area (Greg, 2009). The responsibilities of<br>waste management in Enugu state is now being shared by ESWAMA, the PSPs and the<br>general public. According to Anyaegbudike (2009), ESWAMA is partly funded by the<br>government and internally generated revenue, but eighty-five per cent (85%) of the money is<br>gotten from the inhabitants of the metropolis.<br>FIGURE 1.3: Proposed Draft Structure for ESWAMA<br>SOURCE: Egwu Frank (2008).<br>13<br>Figure 1.4: Map of Enugu Metropolis Road Network Showing the Ten Zones<br>and the only Official Landfill Site (Ugwuaji Land Fill Site)<br>1.5<br>The chequered history of Enugu state waste management was briefly explained in the<br>back-ground study of this research work. The management had suffered lack of waste<br>management equipment, inadequate funding and man-power to handle the various activities<br>of the agency. In an interview granted by the Public Relation Officer of the ESWAMA, Mr.<br>Egwu Frank (2007), he stated that the major challenges facing the management are<br>inadequate funding and operational logistics. In addition to these, he stated that the people’s<br>negative attitude towards waste disposal contributes to the problems of the agency. The<br>operational manager of ESWAMA, Ayaji (2008), in an interview stated that the problems of<br>the agency include: lack of important waste management equipment like excavators,<br>Statement of problem.<br>14<br>bulldozers, pail-loader, tippers and compactors, insufficient buckets (dumpsters),<br>insufficient funds and operational logistics. This problem of insufficient dumpsters is also<br>prevalent in Accra, Ghana (See appendix 41). The available compactors cannot collect all the<br>solid wastes being generated in the metropolis daily. He further stated that the welfare of the<br>workers is not properly considered especially during the last regime of the former<br>administrator of Enugu state (Ayaji, 2008).<br>The Managing Director and Chief executive officer of the ESWAMA, Engr. Greg<br>Anyaegbudike, stated that it costs the agency more than one hundred and forty million<br>(N 140,000,000) nairas to keep the Enugu metropolis clean in a year excluding staff salaries<br>(Anyaegbudike, 2009). The agency at present has one thousand buckets; nine hundred and<br>thirty are being used at Enugu and the other seventy are being used in other parts of the state,<br>eleven compactors, one pay-loader and a tipper. One compactor is being used at Nsukka<br>while the other ten are distributed to the ten zones of the metropolis.<br>Despite all these efforts made by the chief Executive Manager of ESWAMA, the agency<br>still have logistic problems which causes in-efficiency in waste disposal in the metropolis.<br>One unique problem of the agency is that it has only one landfill site located at<br>Ugwuaji (figure 1.4) along Port Harcourt road. Just as it is in Uganda, according to Michael<br>K. Nganda (2007) about half of the waste generated in Kampala, the capital city of Uganda,<br>is collected and disposed of at the only landfill at Kiteezi and as a result of this, less than half<br>of the waste were left in the open, which litters the city whenever the wind blows and<br>whenever rain falls. This explains the incidence of the annual cholera outbreaks during the<br>rainy seasons and the terrible stench from the city areas where the waste accumulated<br>decays. This is the same for Enugu metropolis. All the compactors collecting waste in the<br>metropolis will only empty its content at Ugwuaji landfill site. This had caused the inability<br>of the compactors to collect all the solid wastes generated in the metropolis, which are<br>evident by the open dumps here and there along the roads and filled-up dumpsters are not<br>collected for more than three weeks. Some of these mountains of wastes are seen along<br>major roads in Enugu (see appendix 11 – 53). In some areas, it causes partial or total<br>blockage of main roads resulting to unnecessary traffic jams (appendix 42, 45, 51,52) and<br>also blockage of drainage gutters (appendix 44) The odor oozing out of the wastes irritates<br>inhabitants of the metropolis (appendix 11, 12). Some of the rivers that flow through the<br>15<br>metropolis are contaminated with solid wastes (appendix 23, 31, 32). Also, some good<br>agricultural lands are impoverished by these solid wastes (appendix 24, 25).<br>The compactors are over-used which causes their constant breaks-down, worn-out tyres,<br>burst hydraulic pipes and air pipes, and engine knock (appendix 4-10). The result would be<br>high maintenance cost and inefficiency. Despite all these problems, a good solid waste<br>management approach will help to improve the efficiency of the agency by reducing the long<br>distances travelled by the compactors, thereby reducing maintenance and operational costs.<br>1.6 Objectives of the study.<br>The main objective of this research work is to design an effective waste management<br>system that will reduce the operational cost of ESWAMA and improve its waste disposal<br>efficiency. These specific objectives are:<br>1. To establish nine more landfill sites other than the former one at Ugwuaji which will<br>help to reduce the long distances travelled by the compactors.<br>2. To develop a solid waste disposal schedule that will minimize cost of transporting the<br>waste generated in the metropolis using a mathematical model.<br>3. To compare the result with the existing schedule with respect to efficiency and cost.<br>4. To suggest the use of other waste management methods that will help to reduce the<br>quantity or volume of solid waste that go into the landfill sites.<br>1.7<br>The rate at which solid wastes are beginning to accumulate in Enugu metropolis again is<br>alarming and if nothing is done very fast, Enugu metropolis may become the dirtiest city in<br>Nigeria. The deplorable state of these newly acquired compactors as a result of over-usage is<br>alarming. This study if applied will go a long way in solving the problem of long distances<br>travelled by these compactors in such a way that the operational (transportation) cost will be<br>minimized and the life span of the compactors improved. In addition, this will help the<br>Planning Department of ESWAMA to plan on how to schedule the transportation of the<br>Significance of the study.<br>16<br>waste generated in the metropolis in the future. Finally, this research work will<br>demonstrate how industrial engineering knowledge can be used to solve solid waste disposal<br>problems.<br>1.8 Scope of the Research Work.<br>This research work is designed for solid waste management in Enugu metropolis. It will<br>examine the effect of the population of the metropolis with the waste generation of the area.<br>It will also examine other solid waste management approaches that can help to reduce the<br>amount of wastes that go into the landfill sites.<br>The work will examine the effect of creating nine more landfills on cost of transporting<br>wastes and the efficiency of the new waste disposal method. An appropriate scheduling<br>system will be used to analyse the cost effectiveness of this method from collecting sites to<br>disposal sites. The average distance from the centre of each zone to the landfill site will be<br>used.<br>1.8.1 Some Important Assumptions.<br>In the cause of this research, some important assumptions were made. These assumptions<br>include:<br>1) A centre for each zone was chosen by observation from which measurements of distances<br>(along the roads) were taken from each zone to each landfill site.<br>2) Also, the position of the landfill site in each zone was chosen after considering the factors<br>affecting the establishment of a landfill site.<br>3) The compactors are working at its full capacity and the trucks are assumed to be<br>fully loaded upon leaving the waste collection points.<br>4) Each landfill site can take care of a zone in the metropolis for forty (40) years.<br>5) A centre for each zone was chosen by observation from which measurement of<br>distances were taken from each zone to each landfill site..<br>17 <br></p>