Use of geospatial technologies in the selection of suitable sites for a Wastewater Treatment Plant Case Study: Loitokitok town

Abstract

The County Governments began operations in the year 2013 and this has led to rapid population growth in the county and sub-county headquarters. Due to the increased population, water, soil and air pollutions have been detected in some urban centers including Loitokitok town. The town does not have a sewerage system and the existing methods of handling wastewater, including solid-waste by use of pit-latrines, soak pits and septic tanks are proving inefficient. This research project used geospatial technologies such as GIS modeling processes and Multi criteria decision analysis to locate suitable areas for a wastewater treatment plant in Loitokitok town. The study considered ten variables; major roads, dwelling houses, soils, slope, altitude of the town, distance from the town, water bodies, land use land cover, location of the airstrip and the country borderline with Tanzania. The relevant datasets were collected and processed to cover the study area. The relative weights of the variables where determined through questionnaire responses from experts. Nineteen respondents participated and the resultant weights were computed through the Analytic Hierarchy process. Water bodies’ variable was found to have the highest level of significance at 21%, the country borderline had the lowest at 4% while the other variables had varying significance levels ranging from 5% to 17%. The site location criteria were identified from existing sewerage and sanitation manuals and other previous researches. GIS modeling and analysis were executed to determine the suitability maps for each criterion and the overall suitability map. The overall suitability map depicted that, out of the 246km2 area coverage of the study area; 88.6% of the study area was found to be unsuitable for siting the plant, 10.7% had high suitability level, 0.5% had very high suitability level and 0.2% had moderate suitability level. Eight most suitable sites (Site1 to Site8) were realized and they fall within Kimana, Loolopon and Kuku sub locations in Loitokitok sub-county. The selected sites were compared with previously proposed sites by Wanjohi Consulting Engineers in 2009 and Runji & Partners Consulting Engineers in 2015. Site 5 was found to be near the two sites and the best location for siting the plant. The study achieved it overall objective of determining the most suitable site(s) for a wastewater treatment plant for Loitokitok town.