Impact of Landfill Leachate on Iron Release from Northwest Florida Iron Rich Soils

• Other Authors: Subramaniam, Pawan Kumar (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Civil engineering; Environmental engineering
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-1519

Landfill leachate is blamed for elevated levels of iron in the groundwater monitoring wells downgradient of unlined landfills. It is suspected that the geochemical and geomicrobial iron reduction/oxidation processes are responsible for the iron release to the groundwater. When conditions permit, microbial mediated iron reduction and release may be the mechanism for elevated iron observations in the groundwater. In regions near the landfills, there is also a possibility of iron release due to the oxidation of metallic iron, especially, near the C&D landfills, which can occur under both aerobic and anaerobic conditions. The objective of this research is to investigate whether, and to what extent, microbial activities are responsible for iron release in the regions near landfills in Northwest Florida. For microbial mediated iron reaction processes, we want to testify whether it is an iron reducing process or sulphate reducing process (iron oxidation). In addition, we want to quantify the iron reduction/oxidation rate to provide evidence which mechanism is dominating and responsible for iron release in Northwest Florida. The methodology of this research is to react simulated leachate with soils collected from Northwest Florida in the absence and presence of microbial species cultured from landfill regions where elevated groundwater iron concentrations have been observed. Sixteen landfills of fifteen Northwest Florida counties were sampled and the soil iron content of these samples was quantified. Iron release experiments were then carried out using the sampled soil reacting with leachate samples in the presence of iron reducing bacteria that was pre-cultured using iron rich soil as the base consortia. The variations in pH throughout the experiments were monitored to study the correlation between iron concentration and pH. Iron release was most pronounced for soil samples collected from Walton County Central landfill reacting with the corresponding landfill leachate. The iron release for this site was as high as 275 mg/L within 5 days. On the contrary, minimal iron release was observed for the control, i.e., in the absence of iron reducing bacteria. These observations demonstrated that iron release nearby landfills in Northwest Florida was a microbial mediated iron reduction process. Though this research is focused on Northwest Florida, the results of this research can be applied beyond local perspectives to any region with iron rich soils. === A Thesis Submitted to the Department of Civil and Environmental Engineering in Partial Fulfillment of the Requirements for the Degree of Master of Science. === Fall Semester, 2007. === October 23, 2007. === Engineering, Iron, Ferrous ferric, Landfill, Florida, Northwest, Mineral salt media, Spectrophotometer, Soil iron content, Groundwater, Environmental, Bacterial, Characterization, pH, Quantification, Aerobic, Anaerobic, Artificial leachate, plte counts, C&D Landfills === Includes bibliographical references. === Gang Chen, Professor Directing Thesis; Amy Chan Hilton, Committee Member; Tarek Abichou, Committee Member.