Bioremediation of Mechanically and Biologically Treated Waste Of Bangalore City: An Experimental and Numerical Study

Abstract

Remediation of the existing MSW dumpsites has received considerable attention these days and there is an urgent need to address this issue in order to maintain the over hygiene of the urban environment. An approach consisting of experimental and numerical studies to understand the behavior of the waste to be remediated is essential in this regard. In this study, laboratory scale experimental studies were carried out to characterize the mechanically and biologically treated (MBT) waste of Bangalore city. The physical composition, index, engineering and biochemical properties of the waste which are essential for the design of a bioreactor landfill were estimated. The moisture retention characteristics (MRC) and the hydraulic conductivity of the waste influence the design and performance of the leachate recirculation system in a bioreactor landfill. Estimation of MRC and hydraulic conductivity of waste were carried out under varying conditions of overburden stress and density. Their behavior in the fresh and degraded waste was also estimated to predict its influence on LRS as a function of time. Laboratory scale bioreactor studies to assess the biodegradability of the MBT waste under aerobic and anaerobic conditions were carried out. The performance of the bioreactors in terms of the organic content of waste, the gas generated, leachate characteristics and the settlement were evaluated for around 574 days. Experimental studies representing the methane oxidation process in the biocover systems were studied using anaerobically digested MBT waste as the cover material by means of column studies. The modeling studies consisted of the validating the experimental results of the laboratory scale anaerobic bioreactor using a Landfill Degradation and Transport model (LDAT). Parametric study was conducted using the model to study the influence of various parameters such as the growth rates, initial biomass concentration, pH, moisture content, recirculation rate, ambient temperature, heat transfer coefficients on the biogas production. An approach to incorporate the influence of temporal changes on the performance of the LRS due to variations in the MRC and hydraulic conductivity of waste is proposed. The methodology was verified by performing the hydraulic performance of the LRS using HYDRUS-2D model. The application of both the experimental and numerical studies for remediating an existing MSW dumpsite in Bangalore City is given. This involved studying the existing site conditions, modeling studies to understand the influence of installation of the LRS using HELP model, design of the leachate collection and recirculation system and the control of landfill gas emissions using biocover systems. The overall aim of the study was to explore the possibilities of implementing sustainability practices in landfilling.