Jianyong Shi

One-dimensional model for municipal solid waste (MSW) settlement considering coupled mechanical-hydraulic-gaseous effect and concise calculation

A new model entitled the coupled mechanical-hydraulic-gaseous effect and biochemical degradation for municipal solid waste (MSW) is proposed to simulate and predict the MSW settlement in this study. The coupled model can be used to simulate and predict the distributions of gas and water pressure as well as total waste settlement. Model verification indicates that because of degradation, the excess pore gas pressure increases rapidly and reaches a peak value in a short time, and then it dissipates gradually. But the excess pore water pressure may not always increase at the beginning, which depends on hydraulic conductivity of MSW. Dissipation of the excess pore water pressure is slower than that of the excess pore gas pressure. A waste settlement experiment was conducted in the laboratory using a synthetic MSW. The data was used to verify the developed model, which gave satisfactory results. Based on the experimental results, a new formula is proposed to simulate biochemical degradation.

Biodegradation Behavior of Municipal Solid Waste with Liquid Aspects: Experiment and Verification

AbstractA specially designed, large-scale municipal solid waste (MSW) settlement apparatus was used to conduct experiments in this study. The suction for unsaturated waste in different layers also was measured. The test results show that the deeper the sample, the more saturated it will become during testing, although the initial state of the overall sample is almost the same. The pore gas pressure was measured for different depths of the sample. It is shown that the pore gas pressure varies in different layers. Two sets of experiments were conducted to make the comparisons. For one test, water was added to the sample; for the other test, no water was added. Significant differences were observed in the quantity of gas and leachate produced during contrastive tests. A previous theoretical model was updated and extended to be suitable to new boundary conditions with a liquid supply.

The behavior of compression and degradation for municipal solid waste and combined settlement calculation method

The total compression of municipal solid waste (MSW) consists of primary, secondary, and decomposition compressions. It is usually difficult to distinguish between the three parts of compressions. In this study, the odeometer test was used to distinguish between the primary and secondary compressions to determine the primary and secondary compression coefficient. In addition, the ending time of the primary compressions were proposed based on municipal solid waste compression tests in a degradation-inhibited condition by adding vinegar. The amount of the secondary compression occurring in the primary compression stage has a relatively high percentage to either the total compression or the total secondary compression. The relationship between the degradation ratio and time was obtained from the tests independently. Furthermore, a combined compression calculation method of municipal solid waste for all three parts of compressions including considering organics degradation is proposed based on a one-dimensional compression method. The relationship between the methane generation potential L0 of LandGEM model and degradation compression index was also discussed in the paper. A special column compression apparatus system, which can be used to simulate the whole compression process of municipal solid waste in China, was designed. According to the results obtained from 197-day column compression test, the new combined calculation method for municipal solid waste compression was analyzed. The degradation compression is the main part of the compression of MSW in the medium test period.

Analytical Modeling to Simulate Gas Production for Various Tested Landfill Cells

AbstractThe gas extraction wells installed in landfills are used to control gas emission. The degradation of municipal solid waste (MSW) is the main influencing factor for gas production and migration. The symmetric equation of gas migration was established considering the gas extraction wells and peak behavior of the degradation rate. An analytical solution is presented. The peak behavior of degradation rate can be modeled by an equation. The steady degradation ratio of MSW is related to methane generation potential Lo in the LandGEM model. The extraction and injection tests can be well simulated by the symmetric change theory of gas pressure in landfills. From back analysis of the Brogborough test, both the MSW landfill degradation rate and the peak value of gas pressure increased with sludge addition. The degradation time at peak is less than about 700 days. The peak gas pressure in landfill with added sludge increases by 20%.