Impact of Solid Wastes on Groundwater Quality in Dandora, Nairobi County, Kenya

Abstract

Management of solid waste and related environmental impacts presents a challenge to both developing and developed countries. Dumpsites facilities are responsible for the gradual quality degradation of groundwater reservoirs due to leachate generation and percolation. Dandora dumping site is not considered to be well managed and there is a potential of such observed impacts which contribute to further damage of groundwater quality. This research was conducted in Dandora dumpsite, Dandora division, Nairobi. The general objective of the study was to assess the impact of solid wastes on groundwater quality in Dandora. The study specific objectives were i) to assess the levels of pollutants in leachate produced by Dandora dumpsite and groundwater as compared to National Environment Management Authority guidelines for effluent discharge and Kenya bureau of standards and World Health Organization guidelines for drinking water quality; ii) evaluate the effects of dry and wet seasons on pollutants concentration in groundwater and finally iii) establish the correlation between levels of pollutants in groundwater with respect to distance from dumpsite. The study employed purposive sampling whereby during dry season (Sept-October) and wet season (Nov- December) 36 groundwater samples and 4 leachate composite samples were collected from nine wells and the dumpsite respectively. Physicochemical and biological parameters in leachate and groundwater were analyzed in accordance with standard procedures. Data obtained were analyzed using single-sample t test, dependent t test and the Pearson correlation. The study found that in groundwater the levels of electrical conductivity (p= 0.001), Biochemical oxygen demand (p= 0.02), Lead (p= 0.004), Escherichia coli (p= 0.001) and total coliforms (p= 0.001) were significantly higher than Kenya bureau of standards and/or World health organization guideline for drinking water quality, this makes water unsuitable for consumption. Leachate results indicated that Dandora dumpsite was in anaerobic conditions of waste decomposition characterized by increase of pH, decline of sulphate and organic compounds in leachate: The results also showed that during wet season the levels were higher for Conductivity (p= 0.001), Total dissolved solids (p= 0.002), pH (p= 0.001), Nitrate (p= 0.002), Cadmium (p= 0.05), Lead (p= 0.002) and Chromium (p= 0.02) as compared to dry season. This can be attributed to flushing and infiltration effect of rain water that washed out chemicals contained in refuse. The study further revealed that the levels of pH (r= - 0.70, p= 0.03), Biochemical oxygen demand (r= - 0.95, p= 0.001), Chemical oxygen demand (r= - 0.95, p= 0.001), Phosphate (r= - 0.77, p= 0.01), Chloride (r= - 0.88, p= 0.001), Cadmium (r= - 0.81,p= 0.008), Lead (r= - 0.86,p= 0.003) and Chromium (r=- 0.80, p= 0.009) significantly correlated with distance between wells and dumpsite. Groundwater in Dandora is polluted by solid wastes; therefore it is recommended that groundwater should not be used for human consumption.