1.1. Background of the study
In the world, an averagely about 4 billion tons of municipal solid wastes, MSW are discharged, and an amount of US$ 410 billion per year is spent from collection to recycling of solid waste [1]. The environmental values in rapid economic development, urbanization, and improving life level in cities leads to an increase in the quantity and complexity of generated waste, that representing a phenomenal challenge [2].
Municipal Solid Waste Management, MSWM is the proper management of various components such as generation from source, collection system, storage, transfer and transport, processing and treatment, and final disposal to landfill or dumping site [3]. Solid wastes contain heterogeneous contents of discharge from the urban community as well as the more accumulation of commercial, industrial, residential wastes, and other waste generators.
A mismanaged solid waste transportation has a negative impact on the environment and ecology heath in the community. These are a growing problem for national and local governments to ensure effective management of environmental sanitation and lack of controlled waste management [4]. 2003 WHO report indicated that the total health-care waste per person per year in most low-income countries is anywhere from 0.5 to 3 kg which is one of the cases for increases in health problems to citizens of low-income countries like Ethiopia.
Failure of the municipal solid waste management highly affects public health. It contaminates groundwater as well as surface water and increases air pollutants, leading to uncomfortable living conditions. Therefore an immediate demand to look into the issues of SWM and also improve the capability of town administration to manage SWM with the least cost as much as possible are necessary. Because the solid waste transport cost alone comes to more than half of the total costs incurred in integrated solid waste management, ISWM in major cities of the world [1].
Now a days, integrated GIS technology with a prepared database provides an advanced modeling framework for decision-makers that analyze and simulate various problems related to solid waste management, SWM such as transportation route optimization. Inaddition GIS has been used to model various problems in waste management such as siting of landfills, optimizing the collection and transportation, and others [5].
1.1.1. Existing Municipal Solid Waste Disposal System in Jimma Town
The report of Jimma sanitary landfill environmental and social impact assessment 2013 indicated that the municipal solid waste, MSW of the town collected by the municipal truck openly dumped at southeastern part of the city near the Jimma airport on Bonga road. The dump site is located at about 4 km from the city center which is local name ‘Qofe’. The municipal trucks dispose waste both to the right and left side Bonga road over a length of several hundreds of meters. During dry season the trucks go off road some hundreds of meters, whereas; during rainy season the trucks hardly go off roads; rather dump their load along the road left and right. It is also reported that some farmers request for wastes to be dumped on their farmland as fertilizer and soil enhancement.
1.1.2. ArcGIS Based Solid Waste Management
A geographical information system, GIS is a computerized system that permits to map, model, query, and analyze a large quantity of data within a single database according to their geographical location. It has the capability of making maps that integrate information visualize scenarios present powerful ideas, and develop effective solutions for various purposes. [3].
Solid waste management has used the ArcGIS tools model for the reduction of environmental and geographic related problems [4] by preparing an appropriate database. These reduced environmental problems are such as pollution, erosion problems, health problem, and others. Nikolaos [6], discussed that the model for the municipal solid waste generation and collection is a part of an extended solid waste management system and use a spatial geodatabase, integrated into a GIS environment. [7, 9 and 8] concluded that GIS can assist in analyzing coverage and reallocation of community bins by superimposing service or command area of bins over land-use imagery to find potential placing spots which could later be field checked for suitability and conformation to guidelines.
ArcGIS also used in simulating spatial data for facilitatating collection operations, analyzing optimal locations for transfer stations, and optimizing routes for vehicles transporting waste from residential [7, 10]. The application of this software currently helps in the simulation of reality for a particular phenomenon. A solid waste management, SWM is one of the problematic areas where the problems arise from day to day rapidly. The town municipalities were unable to provide a fully efficient system and even are not able to reach an efficiency of more than half percent [1]. The geographical information system, GIS extension networkanalyst tool, NA toolbox contains tools that achieve the activities of network analysis and network dataset maintenance. It is a powerful extension of ArcGIS that provides network-based spatial analysis including routing, travel direction, closest facility, and service area analysis [12] and used for transportation route optimization in the present study.
1.2. statement of the problem
Urban transportations, particularly the phenomenon of congestion and pollution are the major problem of society [13]. The globalization of the economy leads to a rapidly growing exchange of goods, disposing of wastes, and other purposes by transportation on our planet. Collection and transportation of MSW was constituting more than 75% of the total SWM budget [14]. Therefore there is a high demand for cost reduction by using optimization techniques were the present study use a network analyst tool, NA to optimize solid waste, SW transportation route optimization.
In the town, there was an overflow of MSW due to improper transportation frequency to the disposal site (Fig. 1). This frequency of transportation affected by various factors and the main affecting factor is the existing transportation route was not properly designed. According to the information obtained from a government authority, Jimma town municipality has no design for the transportation route and frequency of transportation of the waste.