Municipal Solid Waste Landfill Sites Selection for Visakhapatnam City under Vision 2020 Using GIS and AHP

Municipal solid waste management is considered as one of the most serious environmental and social issue challenging municipal authorities in all major cities in India. The main problem is selecting a suitable landfill site for Solid Waste Management (SWM). Land filling is now accepted as the most widely used method for addressing this problem in all countries of the world. However, appropriate site selection for land filling is a problem in waste management and therefore needs to be addressed. This study aims at selecting a suitable solid waste landfill site for Visakhapatnam City, India for its future needs. A set of four main criteria and 13 sub criteria are considered for identifying suitable sites. The combination of GIS and the Analytic Hierarchy Process (AHP) has been used to give weights to different criteria. Relative Importance Weightage (RIW) of each parameter over the other is calculated by pair-wise comparison using the 9-point scale. The suitability index (0.1-0.6) values are determined for five classes (excellent, good, moderate, poor and very poor) for land fill siting. The study also aims at generating an optimal route to the suitable sites identified from the waste transfer station by using Network Analyst module of ArcGIS software such that the total system cost can be minimized.

2011). In fact, landfill is an essential part of any waste management system and is a widely used method. (Mahini and Gholamalifard 2006). Of the various techniques of solid waste management, land filling is the most popular and widely prevalent technique in India. According to an estimate, per capita municipal solidwaste generated daily in India ranges from a low of 100 g in small towns to a high of over 500 g in big cities (Jayasheela et al. 2007). This translates into approximately 80,000 metric tonnes daily or 30 million metric tonnes annually. Further, only about 60 to 80% of the waste generated is collected and disposed of at present, while the rest is allowed to decay on the roads, streets, or in the drains etc. This poses serious health and environmental problems for the city dwellers (Sunil Kumar  Visakhapatnam is the second biggest city in undivided Andhra Pradesh after Hyderabad. Once a small fishing village has evolved into major port city in south India over the decades and considered as the fastest growing city in India. The total area of the city is 540 sq.km (GVMV, 2012) and with Greater Visakhapatnam Municipal corporation jurisdiction of 111sq.km with a growing population of more than 30.82 lakhs. The city is the biggest economic hub with both public and private sector undertaking like Visakhapatnam Steel Plant, Visakhapatnam Port, National Thermal Power Corporation, Hindustan Petroleum Corporation, Hindustan Zinc, Hindustan Shipyard, Bharat heavy Plates and Vessels and any more private companies are located in and around the city generating huge amounts of waste. The Public Health and Sanitation Department of GVMC is responsible for collection, transportation and disposal of solid waste generated in Visakhapatnam City.
Among all processes involved in solid-waste management including collection, transportation, processing, recycling and land filling, disposal of waste in a suitable landfill is the most crucial one because wastes dumped in open space or in unsuitable sites are a serious threat to environment and human health (Sunil Kumar et.al 2012). Selection of a ‗landfill-site' is an important component of urban planning, and belongs to the domain of science, social sciences, public health and planning (Yagoub & Buyong ,1998). Selection of a landfill for disposal of solid wastes requires processing and evaluation of a significant amount of spatial data with respect to various parameters governing the suitability of a site (Ojha et al. 2007). . Using GIS and AHP, the present study endeavors to locate best suitable sites for GVMC with a vision for 2020.

Material and methods:
In the present study three different sources are used to collect the required data. The three sources are remote sensing satellite data from National Remote Sensing Agency (NRSA), Survey of India (SOI) topo- sheets and related Government and private agencies for existing data products. The data types, important features and corresponding data sources used in the present study are listed in Table 1. Description of the study area: The study area is located approximately between 82°47'30.8‖ and 83°28'42‖ East Longitude and between 17°26'30‖ & 18°03'52‖ North latitude. The ground levels vary from 2 meters to 600 meters above mean sea level (MSL). Visakhapatnam is the second biggest city in undivided Andhra Pradesh after Hyderabad. Once a small fishing village has evolved into major port city in south India over the decades and considered as the fastest growing city in India. The total area of the city is 540 sq.km (GVMV, 2012) and with Greater Visakhapatnam Municipal corporation jurisdiction of 111sq.km with a growing population of more than 30.82 lakhs. According to GVMC at present the quantity of waste generated is around 737 tons per day with an average per capital solid waste generated by the city works out to around 489 gm/capital/day. The Public Health and Sanitation Department of GVMC is responsible for collection, transportation and disposal of solid waste generated in Visakhapatnam City.

Methodology Adopted for Analysis:
In the wake of a huge amount of wastes coming from different zones, the current disposal site at Kapulapadu disposal site is not only overfilled but also the height of the dumping mound has gone up to nearly 15 m from the ground. An alternate sites for dumping of solid wastes is, therefore, urgently required. In order to locate suitable sites in the vicinity of Visakhapatnam city, Remote Sensing, Geographical Information Systems (GIS) and a Multi criteria decision analysis technique viz., Analytical Hierarchy Process (AHP) model has been used (Thomas L. Saaty 1980). The study also aims at generating an optimal route to the suitable sites identified from the waste transfer station.
For the present study, the spatial -AHP technique was applied to identify and rank potential sites for solid waste disposal. In the first phase, ERDAS and ARC/INFO software are used to generate topographic, thematic and spatial data corresponding to layer including settlements roads, topography, geology, land use, geomorphology, aquifers and surface waters, soil etc. from IRS-P6, LISS-III satellite imagery, Survey of India topo maps, existing datasets and field data. The spatial and attribute digital database generated are further integrated for subsequent data analysis in GIS.
In the second phase, criteria to be considered for municipal solid waste disposal sites selection are identified and broadly grouped into exclusionary and non-exclusionary criteria. Fig:2

Identification of Decision factors:
The primary factors that contribute significantly to the site selection criteria include the topographical information, geological factors, factors ensuring environmental acceptability, hydrological factors, physical feasibility and political restrictions. These factors were classified into two groups, namely, the exclusionary criteria and the non-exclusionary criteria.
Relevant exclusionary criteria were also obtained from the guidelines of Municipal Solid Wastes (Management and Handling) Rules, 2000, Ministry of Environment and Forests, New Delhi. Based on these criteria, buffer maps depicting the unsuitable areas surrounding major roads, rivers, habitation, lineaments, airport etc. for construction of a landfill are prepared.
All the non-exclusionary criteria are arranged in a hierarchical structure. The non-exclusionary criteria are the ones for which the pair-wise comparison of AHP is applicable. The Level I comprises the goal i.e., selection of best site for solid waste disposal which in turn comprises of four decision factors arranged at Level II of this structure viz., geological, topographical, environmental; and hydrological criteria. Geological criteria are in turn divided in to two sub-factors as geology and soil at Level III. Similarly, topographical criteria are subdivided into slope, land use / land cover and geomorphological characteristics; hydrological criteria are classified as ground water potential, infiltration rate and groundwater table; environmental criteria are divided into groundwater quality and air quality at Level III. All the criteria at Level III are converted into spatial maps from satellite imagery and SOI topo sheets using Remote sensing and GIS software. The remaining attributes are placed at level IV and further rated according to their importance for landfill siting using the 9-point scale of Saaty (Wael M. et.al 1996). Fig.3

RIW of Decision criteria at Level I to Level IV:
The criteria placed at level II of the hierarchical structure include the hydrological, topographical, environmental and geological factors. The hydrological parameters comprising of groundwater potential, infiltration rate and groundwater table are given absolute importance over topographical, environmental and geological criteria for selection of landfill site in the present study area. Since the immediate impact of any landfill is the contamination of groundwater resource caused due to leaching of pollutants from the disposal site, hydrological conditions are given higher weightage compared to other criteria. Once an aquifer is polluted, its impact can be felt on the entire fracture zone making the groundwater unsuitable for any further use. Change in climatic conditions also have an impact on the groundwater potential and depth and since the life of a landfill is proposed to be minimum of ten years, utmost care is taken to prevent contamination of underlying groundwater. Topographical criteria comprising of land use / land cover, slope and geomorphology are given secondary importance with respect to site selection, keeping in view the morphological and terrain conditions of the present study area. Once the hydrological conditions is known, the next step is to select a site, which is vacant and not suitable for any development activity and is easily accessible. Environmental criteria viz., groundwater quality and air quality are placed at third level since the impact on the environment is observed only after a landfill is set-up and the waste is dumped. Geological criteria for the present study is given least priority when compared to hydrological, topographical and environmental criteria, since there is very little variation in the geological condition of the study area i.e. 90% of the study area falls under granitic terrain. The relative importance weight assigned to each hierarchy element is determined by normalizing the eigenvector of the decision matrix. Eigenvector values are estimated by multiplying all the elements in a row and taking the Nth root of the product, where N is the number of row elements. Normalization of the eigenvector is accomplished by dividing each eigenvector element by the sum of the eigenvector elements (Siddiqui et al, 1996). The calculation of the estimated Eigen element (EEE) and RIW at different levels of decision hierarchy are prepared. Level 1 and Level II calculation of EEE and RIW are given below.   Aggregating the RIW to Calculate Suitability Index: After the RIW of each element of each theme to be considered for site selection are calculated, the individual weightages are aggregated and evaluated for estimation of the suitability index. The suitability index for each cell is determined and applied in Arc View GIS software for the selection of a final waste disposal site. The suitability index values obtained in the present study ranged in between 0.1046 and 0.5821. The higher the suitability index, the more suited it is for landfill siting. Relative importance weightage (RIW) of each feature of the thematic layers is calculated and used in the estimation of suitability index values. The suitability index is determined by aggregating the RIW at each level of hierarchy. Based on the suitability indices values obtained, entire area is categorized into five classes, as excellent class with suitability index ranging from 0.5 to 0.6, good class with suitability index ranging from 0.4 to 0.5, moderate class with suitability index ranging from 0.3 to 0.4, poor class with suitability index ranging from 0.2 to 0.3 and very poor class with suitability index ranging from 0.1 to 0.2 with respect to landfill siting. Higher the suitability index, the more suited is the site for waste disposal and lower the value, lower is the suitability. The suitability map prepared for the present study is depicted in Fig:4 GIS analysis led to a short list of sites, the attribute evaluation (distance from the point of waste generation, area covered, distance to nearest road or water body, population density surrounding the site etc.) of each of these individual sites was performed to determine which site possessed the best compromise of features for developing a landfill and are selected and ranked accordingly. Therefore, keeping in view the aerial extent of the site, ground water levels, existing land use / land cover, geomorphology and the distance of the site from the point of waste generation, few sites from each of the excellent, good and moderate suitability classes were selected. Apart from the above, the scrub forest is not considered for selection of sites. The list of sites selected in present study is given in table 5