Leachate characteristics: Potential indicators for monitoring various phases of municipal solid waste decomposition in a bioreactor landfill

Abstract

Leachate is a contaminated liquid generated during the bio-chemical decomposition processes of municipal solid waste (MSW) that occurred at semi-solid or solid-state in a bioreactor landfill (BLF). Conceptually, leachate from a BLF is analogous to the urine generated in the 'human body', on which the medical practitioners rely to diagnose and remediate ailments. In line with this practice, to monitor the complex MSW decomposition processes, prolonged investigations were performed to establish the temporal variation of different chemical parameters (such as pH, electrical conductivity, chemical oxygen demand, organic- and inorganic carbon, nitrate- and ammonium-nitrogen, sugars and volatile fatty acids) of the leachate collected from different cells (age≈ 6-48 months) of a fully functional BLF in Mumbai, India. Furthermore, to understand the effect of the climate, MSW composition and landfill operating conditions on the rate of the decomposition process, chemical parameters of the leachate obtained from a landfill located in the central part of Poland were compared with the BLF. The study reveals that the chemical parameters, except for the pH, evince a rapid reduction with time and attain a constant value, which indicates the 'stabilized MSW'. Also, native microorganisms that are an integral part of MSW consume volatile fatty acids within a year in the BLF, which facilitate the rapid transformation of the decomposition process from acidogenesis and acetogenesis to the methanogenesis phase. It is worth iterating here that based on the long-term field study, a convenient and efficient methodology, which is currently missing from the literature, has been established to understand the kinetics of different phases of anaerobic decomposition. This study would be very helpful to the landfill operators, who are interested in accelerating MSW decomposition by augmenting leachate properties.

Keywords: Bio-chemical decomposition; Bioreactor landfill; Leachate characterization; Municipal solid waste.