Stabilization of Expansive Soil Using Biomedical Waste Incinerator Ash

Expansive soils undergo high volume change due to cyclic swelling and shrinkage behavior during the wet and dry seasons. Thus, such problematic soils should be completely avoided or properly treated when encountered as subgrade materials. In the present study, the biomedical waste incinerator ash and lime combination was proposed to stabilize expansive soil. Particle size analysis, Atterberg limits, free-swell, compaction, unconfined compression strength, and California bearing ratio tests were conducted on the natural soil and blended with 3%, 5%, 7%, 9%, and 11% biomedical waste incinerator ash (BWIA). The optimum content of BWIA was determined based on the free-swell test results. To further investigate the relative effectiveness of the stabilizer, 2% and 3% lime were also added to the optimum soil-BWIA mixture and UCS and CBR tests were also conducted. In addition, scanning electron microscopy (SEM) tests for representative stabilized samples were also conducted to examine the changes in microfabrics and structural arrangements due to bonding. The addition of BWIA has a promising effect on the index properties and strength of the expansive soil. The strength of the expansive soil significantly increased when it was blended with the optimum content of BWIA amended by 2% and 3% lime.

Numerical modeling of clogging of landfill leachate collection systems with co-disposal of municipal solid waste (MSW) and incinerator ash

The influence of co-disposal of municipal solid waste (MSW) and incinerator ash used as daily cover on the clogging of leachate collection systems (LCSs) from landfills is examined. The “BioClog” model is used to simulate the fate and transport of the nine leachate constituents most responsible for clogging the LCSs as they move through the porous media. It then calculates the thicknesses of five films that attach to the porous media and the effect of this clog mass–volume on the porosity and hydraulic conductivity of the granular material. Then it models the consequent growth in the leachate mound with increasing clog mass over time until the service life of the LCS is reached. The modeling shows that the concentrated source of leachable minerals in the incinerator ash accelerates the clogging rate and reduces the service life of the LCSs compared to inert daily cover. If an LCS is not designed to accommodate these higher concentrations of cations in the influent leachate during the landfill operating period, the ash can significantly reduce the LCS service life. Means of extending LCS service life are discussed. A practical technique is also utilized to estimate the service life of LCSs with conservative and reasonable agreement with BioClog.