Innovative Fe(III)-dosed Anaerobic Biological Treatment System: From Fe and S Biogeochemical Reactions to Engineering Process
Innovative Fe(III)-dosed Anaerobic Biological Treatment System: From Fe and S Biogeochemical Reactions to Engineering Process By Musfique Ahmed In moving toward more sustainable wastewater management, anaerobic treatment is gaining increasing popularity due to its simplicity, low energy requirement, low sludge production and less emission of greenhouse gases compared to typical aerobic wastewater treatment systems. Electron acceptors such as nitrate, sulfate, and CO2 have been used in various
... aerobic processes for removal of organic matters from wastewater under anoxic or anaerobic environments. In energy producing regions, ferric iron, Fe(III), is a predominant element in iron containing wastes such as acid mine drainage (AMD) and coal ash, which can potentially be used as a source of iron in novel anaerobic wastewater treatment. Such an iron-based treatment approach can offer multi-faceted benefits over existing treatment methods including use of ironcontaining wastes, no aeration, unique reaction mechanisms for coagulation, sulfide control, organic micropollutant removal, and useful sludge byproducts. The overall goal of this research was to develop an innovative Fe(III)-dosed anaerobic wastewater treatment process through incorporating known and novel biogeochemical reactions of iron in an engineered biological system. The major research objectives include (1) identifying the critical factors and investigating their effects on the treatment performance of Fe(III)-dosed wastewater treatment; (2) developing a continuous Fe(III)-dosed anaerobic biological treatment system and examining its technical feasibility and potential issues in long-term operations; (3) developing a method for transforming the sludge materials from the Fe(III)-dosed bioreactor into magnetic byproducts; and (4) exploring the applicability of this Fe(III)-dosed treatment method for nutrient removal and recovery. A detail literature review was first conducted to evaluate the suitability of using iron reduction for wastewater treatment and identify critical factors affecting the treatment. Several factors were identified that affect organics oxidation coupled to iron reduction, including the types of the ferric compound, microorganisms, ferric bioavailability and availability of substrate. Amorphous iron materials (e.g. iron sludge from AMD) with large surface areas and high ferric dissolution rates have great potential to be used in Fe(III)-dosed wastewater treatment process to enhance ferric bioavailability to iron reducers. Given the significant levels of sulfate (SO4 2-) in wastewater, sulfate reduction is expected to be co-occurring with iron reduction in the iron-dosed anaerobic treatment. Shift in microbial composition in relation to ferric and sulfate concentrations (expressed as Fe/S ratio) and their effects on organics removal are important knowledge gaps for developing such treatment technology. In particular, there is a need to understand the nature of the relationships between iron reducing bacteria (IRB) and sulfate reducing bacteria (SRB) (i.e., symbiotic or competitive) to identify optimal operating conditions for this type of wastewater treatment. Batch experiments on iron-dosed anaerobic biological treatment of wastewater under three different molar Fe/S ratios (1, 2 and 3) showed positive correlation between organics (chemical oxygen demand, COD) oxidation rate and Fe/S ratio. Microbiological analysis suggested that both Firstly, I would like to thank my Ph.D. supervisor Dr. Lian-Shin Lin, whose professional knowledge, academic experience, guidance, mentorship and continuous support have played the most significant part in my doctoral study and professional career development. His guidance assisted me in designing experiments, writing manuscripts and dissertation and overall in my progress as a researcher. I am truly grateful to Dr. Michael J. Wilkins for his constant support as an external member of my Ph.D committee, specifically while carrying out the microbiological study of my research and during preparing manuscripts. Furthermore, my whole-hearted gratitude goes to my other committee members as well: Dr.