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A case study on establishing the state of decomposition of municipal solid waste in a bioreactor landfill in India

Estimation of temporal changes undergone by municipal solid waste (MSW) in its physico–chemico–geomechanical properties in a bioreactor landfill (BLF) is essential for: (i) efficient landfilling, (ii) establishing the state of decomposition of MSW with time and (iii) deciding upon the appropriate time to initiate landfill mining. To achieve this, a series of destructive (DTs) and non-destructive tests (NDTs) can be conducted on the MSW samples in the BLF. With this in view, several DTs were conducted on these samples retrieved from different depths of the two cells of a fully operational BLF in Mumbai, India. Subsequently, the physical and chemical properties of these samples such as composition, moisture content, volatile solids (VS), elemental content, lignocellulosic content (i.e. cellulose, hemicellulose and lignin content) and bio-methanation potential, were determined by following the laboratory testing, as a function of time. Also, NDTs such as cone penetration test and multichannel analysis of surface waves were conducted on these cells of BLF to obtain geomechanical parameters (viz. cone resistance, sleeve resistance, friction ratio and shear wave velocity) of the MSW. Based on the data obtained from these tests, and reported in the literature, it has been observed that the VS, elemental content, lignocellulosic content and bio-methanation potential of MSW exhibits very well-defined trends, as compared to the geomechanical parameters, with time. Furthermore, it has been observed that the VS, hydrogen-, carbon- and nitrogen-content reduce significantly (≈62%, 70%, 50% and 30%, respectively), following an exponential decay, until the critical time (tcr) (≈4 years) has been achieved. As, beyond tcr these parameters remain practically unchanged, which corresponds to the ‘stabilized MSW’, mining of the BLF can be initiated without further delay.