Diffusion study of municipal solid waste contaminants in compacted lateritic soil treated with bacillus coagulans

Abstract

The diffusion of municipal solid waste (MSW) contaminants in compacted lateritic soil-Bacillus coagulans (B. coagulans) mixture was studied. Diffusion test for single reservoir, decreasing source was adopted. Soil samples were treated with B. coagulans at one-third (1/3) pore volume in stepped suspension density of 0, 1.5 × 10 8 , 6 × 10 8 , 1.2 × 10 9 , 1.8 × 10 9 and 2.4 × 10 9 cells/ml, respectively, before compaction. Specimens were prepared at optimum moisture content (OMC) of British Standard heavy (BSH) compaction energy. Cementation reagent containing 3 g Nutrient broth, 20 g urea, 10 g NH4Cl, 2.12 g NaHCO3 and 2.8 g CaCl2 per litre of distilled water was injected by gravity in three (3) cycles of 6 hours interval into the compacted specimens. Thereafter, the specimens were sealed at the top with plastic sheets with small openings for the sequential introduction of water and leachate for 21 days and 69 days, respectively, to simulate field condition. Results obtained show that diffusion testing water content, pH and electrical conductivity within the soil column decreased with depth. Generally, all the cations considered had diffusion coefficient (D * ) and tortuosity factors (a) values that increased with increase in B. coagulans suspension density. However, Mg 2+ had value that initially decreased from 5.98 × 10 -9 at 0 cells/ml to a minimum value of -4.30 × 10 -8 at 1.5 × 10 8 cells/ml and thereafter increased to 1.64 × 10 -9 at B. coagulans suspension density of 2.4 × 10 9 cells/ml. The apparent D * and a values for the anions considered initially decreased to a minimum and thereafter increased. The pore fluid concentration profile for the numerous chemical classes tested showed that the compacted lateritic soil B. coagulans mixture can attenuate K + and Cl – ions in MSW containment application.