Explore the vast range of titles available.

Large quantities of sludge produced from acid mine drainage (AMD) treatment require proper disposal due to their potential environmental impacts. Sludge handling and disposal practices are used to address the environmental concerns, and they represent significant economic liability. As a sustainable management strategy, utilization of AMD sludge for beneficial applications can not only eliminate or alleviate the need of disposal, but create value from the materials. In particular, coal mine drainage sludge (CMDS) can potentially be used for various applications due to its high ferric content. However, conventional coal mine drainage (CMD) treatment and sludge disposal practices do not necessarily produce sludge with optimal properties for the applications. This calls for development and implementation of application-driven treatment and sludge management practices to generate sludge materials tailored for the target applications. This study systematically characterized causal linkages between various CMD treatment and sludge disposal factors and sludge properties reported in literature. It also reviewed and documented optimum sludge properties for beneficial applications including adsorptive pollution control, microbially facilitated ferric reduction, and catalytic degradation of wastes. The systematic understanding was then used to develop CMD treatment and sludge disposal guidelines that would facilitate production of application-specific sludge materials. Such an application-driven CMDS management approach, if successfully implemented, is expected to bring about modernization of waste management infrastructure and create values in mineral producing regions.

This study explicated the functional activities of microorganisms and their interrelationships under four previously reported iron reducing conditions to identify critical factors that governed the performance of these novel iron-dosed anaerobic biological wastewater treatment processes. Various iron-reducing bacteria (FeRB) and sulfate reducing bacteria (SRB) were identified as the predominant species that concurrently facilitated organics oxidation and the main contributors to removal of organics. The high organic contents of wastewater provided sufficient electron donors for active growth of both FeRB and SRB. In addition to the organic content, Fe (III) and sulfate concentrations (expressed by Fe/S ratio) were found to play a significant role in regulating the microbial abundance and functional activities. Various fermentative bacteria contributed to this FeRB-SRB synergy by fermenting larger organic compounds to smaller compounds, which were subsequently used by FeRB and SRB. Feammox (ferric reduction coupled to ammonium oxidation) bacterium was identified in the bioreactor fed with wastewater containing ammonium. Organic substrate level was a critical factor that regulated the competitive relationship between heterotrophic FeRB and Feammox bacteria. There were evidences that suggested a synergistic relationship between FeRB and nitrogen-fixing bacteria (NFB), where ferric iron and organics concentrations both promoted microbial activities of FeRB and NFB. A concept model was developed to illustrate the identified functional interrelationships and their governing factors for further development of the iron-based wastewater treatment systems.

Anaerobic treatment processes have the advantages of cost-effectiveness, energy efficiency, low sludge yield and potential of resource recovery over conventional aerobic treatment methods and have been gaining increasing attention as an approach for future wastewater management. An important feature of anaerobic processes is the use of alternative electron acceptors to oxygen, which renders treatment flexibility in using redox active elements such as iron and sulfate from other waste materials. Co-treatment of acid mine drainage and municipal wastewater, as an example, has been shown to be an effective method for removing organic materials, metals, and phosphate from the both wastes. It also suggested the applicability of ferric reduction process in wastewater treatment. Most of the previous studies on ferric reduction process and iron reducers were conducted in natural systems such as sediments, soils and groundwater. This paper reviews the significance and fundamentals of the ferric reduction process, its utility for organics oxidation, controlling factors, reaction kinetics, microbial processes of iron reduction and its ecology. The paper also evaluates the suitability and discusses future aspects of using iron reduction for wastewater treatment. Knowledge gaps are identified in this paper for developing such innovative wastewater technology and process optimization.

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 anaerobic 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 iron reducers and sulfate reducers contributed to this organic oxidation. Maximum COD oxidation rate, Vmax estimated from Michaelis-Menten model ranged from 0.47 mg/L×min to 1.09 mg/L×min as Fe/S ratio increased from 1 to 3. A positive correlation was also observed between COD oxidation rate and the relative abundance of iron reducers, and both increased with the Fe/S ratio.Long-term continuous wastewater treatment using an anaerobic bioreactor dosed with ferric iron showed satisfactory COD removal of 84 ± 4%, 86 ± 4% and 89 ± 2% under Fe/S molar ratio 0.5, 1 and 2 respectively. Fe/S ratio was also observed to regulate the effluent quality by removing excess sulfide from aqueous phase with increasing quantity of ferrous through ferrous sulfide precipitation. The sludge materials contained both biomass (20-40 w/w%) and inorganic precipitates (80-60 w/w%) with the inorganic fraction increasing with Fe/S ratio. Spectroscopic and chemical elemental analyses indicated that the inorganic fraction of the sludge materials mainly contained FeS and FeS2. Microbiological analyses of the sludge materials identified Geobacter sp., Geothrix sp. and Ignavibacteria sp. as putative iron reducers, and Desulfovibrio sp., Desulfobulbus sp., Desulfatirhabdium sp., Desulforhabdus sp. and Desulfomonile sp. as putative sulfate reducers.

COVID-19 caused a significant public health crisis worldwide and triggered some other issues such as economic crisis, job cuts, mental anxiety, etc. This pandemic plies across the world and involves many people not only through the infection but also agitation, stress, fret, fear, repugnance, and poignancy. During this time, social media involvement and interaction increase dynamically and share one’s viewpoint and aspects under those mentioned health crises. From user-generated content on social media, we can analyze the public’s thoughts and sentiments on health status, concerns, panic, and awareness related to COVID-19, which can ultimately assist in developing health intervention strategies and design effective campaigns based on public perceptions. In this work, we scrutinize the users’ sentiment in different time intervals to assist in trending topics in Twitter on the COVID-19 tweets dataset. We also find out the sentimental clusters from the sentiment categories. With the help of comprehensive sentiment dynamics, we investigate different experimental results that exhibit different multifariousness in social media engagement and communication in the pandemic period.

COVID-19 caused a significant public health crisis worldwide and triggered some other issues such as economic crisis, job cuts, mental anxiety, etc. This pandemic plies across the world and involves many people not only through the infection but also agitation, stress, fret, fear, repugnance, and poignancy. During this time, social media involvement and interaction increase dynamically and share one’s viewpoint and aspects under those mentioned health crises. From user-generated content on social media, we can analyze the public’s thoughts and sentiments on health status, concerns, panic, and awareness related to COVID-19, which can ultimately assist in developing health intervention strategies and design effective campaigns based on public perceptions. In this work, we scrutinize the users’ sentiment in different time intervals to assist in trending topics in Twitter on the COVID-19 tweets dataset. We also find out the sentimental clusters from the sentiment categories. With the help of comprehensive sentiment dynamics, we investigate different experimental results that exhibit different multifariousness in social media engagement and communication in the pandemic period.