ENHANCED BIOMETHANATION FROM MUNICIPAL SOLID WASTE (MSW):CONCENTRATION AND MESH SIZE EFFECTS OF ZERO VALENT IRON (ZVI)-MEDIATED HYDROGEN PRODUCTION

Municipal Solid Waste (MSW) is the collection of everyday items that are discarded by a local community. The waste contains various organic and inorganic items such as food scraps, paper, plastic, and wood. Due to rapid population increases and vast development; MSW is becoming an issue. Many waste management operations are looking into ways to minimize overhead costs, increase the capacity of landfills, and/or enhance biodegradation of the MSW at a faster rate.

Methanogens are microorganisms from the domain Archaea that produce CH₄ in anoxic conditions such as landfills. Certain methanogens can use H₂, including H₂produced by cathodic depolarization-mediated oxidation of native iron to produce methane. In this project, enhancing methanogens by utilizing Zero Valent Iron (ZVI) as an exogenous H₂ source was looked to as a possible solution to this global waste management problem.

In this experiment, triplicate microcosms were prepared with MSW from Salt River Landfill (SRL) located in Scottsdale, AZ that is estimated to be have been buried for ~20 years. The microcosms were operated in semi-batch mode at 90% gravimetric moisture content. Three different mesh sizes of ZVI were utilized; Nano ZVI (NZVI), Micro ZVI, and Near Micro ZVI (C.L. ZVI). Three different concentrations were employed; 0.1 g/L, 1.0 g/L, and 5.0 g/L.

NZVI [mid] had a high CH₄ value of 22.7902 mmol/L, high H₂ value of 8.7664 mmol/L, and high conductivity value of 4573.747 us/cm. NZVI [high] had a high CH₄ value of 22.7902 mmol/L, high H₂ value of 8.7664 mmol/L, and a high Conductivity value of 6301.5337 us/cm.

The data collected suggests that increased surface of the ZVI in among the [high] and [mid] treatments correlate with greater CH₄ volume being generated, optimum pH for biomethanation to occur, and peak H₂ production and conductivity. Deploying NZVI and Micro ZVI at [mid] & [high] and concentrations in between, should further be explored as possible solutions to enhance biomethanation in bioreactor landfill operations.