ABSTRACT

The study was carried out at Uyo Municipal Solid Waste (MSW) dumpsite to investigate the effects of MSW leachate on soil and water quality as well as modeling of leachate transport in soil at Uyo waste dumpsite. Samples were collected in both wet and dry season. A total of nine composite MSW samples were collected in each season and characterized.  A total of twenty- seven leachate, stream and borehole water samples were collected in each season for laboratory analyses to test for seasonal effects of leachate transport in the soil. Two sets of soil samples were collected; samples for soil quality analysis and samples for leachate transport modeling. Samples for soil quality analysis were collected at five intervals namely 0m (dumpsite), 10m, 30m, 50m and 200m away from dumpsite which were represented by L1, L2, L3, L4 and L5 and at three designated depths of 0.3m, 0.6m and 0.9m also represented by D1, D2 and D3 respectively.  Infiltration runs were conducted beside each of the three leachate monitoring pits within the dumpsite with synthetic leachate and thereafter, core samples were collected beside each infiltration points from nine designated depths with core cylinders measuring 0 – 0.10, 0 - 0.20, 0 - 0.30, 0 - 0.40, 0 - 0.50, 0 - 0.60, 0 - 0.70, 0 - 0.80 and 0 - 0.90m in height and 0.82cm internal diameter for modeling leachate transport in the soil. Data collected were subjected to descriptive and inferential statistics while the least square regression analysis was employed in validation of the leachate transport model. Results showed that vegetable/ food wastes accounted for 42.79 % of MSW in the dumpsite followed by nylon with 23.24 % to plastics with 11.02 % while glasses had the least (4.88 %).  Chemical analysis of leachate revealed that it is acidic with high concentration of anions and cations. Physicochemical properties of stream water within the dumpsite environment were below the World Health Organization (WHO) standards in terms of hydrogen ion concentration (pH), electrical conductivity, nitrate, phosphate, sulphur and the heavy metals while properties of borehole water namely pH, minerals and heavy metals were within WHO permissible limits. The findings also showed that soils of L1 and L2 were not significantly different (p>0.05) in physical properties but were significantly different (p>0.05) from that of L3, L4 and L5 in chemical properties. Also, correlation results showed that there was significant relationship between particle size fractions and moisture content with other soil properties in the dumpsite soil.  The result also showed that transport of leachate and contaminants in the dumpsite soil is in the form  (  leachate flux, C is the transmissivity coefficient,  is the thickness of the soil, n is the non linear exponent) while their validation equations showed that the observed leachate flux predicted the estimated ones perfectly with very high R² of over 95 %. With high cost of field experiment, the model is therefore recommended for use in Uyo soil and locations with similar hydraulic conditions like Uyo.