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Iron Particles in Freshwater
Published in Jacques Buffle, Herman P. van Leeuwen, Environmental Particles, 2019
William Davison, Richard De Vitre
Truly steady-state conditions rarely apply in lakes and rivers, but a pseudosteady state may sometimes be approached. Under certain circumstances lakes may permanently stratify. The bottom waters, or hypolimnion, become enriched in dissolved components which provide a density gradient that helps to prevent complete mixing.31,32 Oxygen is completely removed from these bottom waters, allowing Fe(II) to accumulate. An iron cycle is established about the redox boundary in the mid-water region where upwardly diffusing Fe(II) is oxidized. The iron particles which are produced then sink back into the reducing zone where they complete the cycle which Campbell and Torgensen32 have called the “ferrous wheel”. In one well-studied Canadian lake,32 where the deep waters had a mean renewal time of 2.5 years, Fe(II) reached concentrations of 4.2 mmol dm−3. Ninety percent of the Fe(II) diffusing upwards was returned to the hypolimnion via the redox cycle, resulting in a mean residence time for iron in the lake of 15 years. The remaining 10% was lost from the lake by flushing. To preserve steady state this loss must be compensated by a supply of fresh, reducible iron entering the lake. The additional iron stokes the “ferrous wheel” by either dissolving at the redox boundary or at the sediment water interface.
Heavy Metal Bioprecipitation
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Graciana Willis, Edgardo R. Donati
Sulfate-reducing microorganisms play an important role in the geochemical carbon and sulfur cycles. They are widely distributed in a large variety of anaerobic marine, terrestrial, and subterrestrial ecosystems and can coexist along with another anaerobic microorganism. These interactions are particularly important in both oxic/anoxic interface and in the deeper anoxic regions (Thauer et al., 2007). In the last years, several studies on the isolation and identification by molecular approaches of SRM from these environments were reported. Falagan et al. (2014) analyzed the indigenous microbial communities of two extremely acidic and metal-rich stratified pit lakes located in the Iberian Pyrite Belt (Spain), using a combination of cultivation-based and cultured independent approach. SRM belonging to Desulfomonile and Desulfosporosinus genus were isolated from the chemocline zone. Other microorganisms that take part in the iron cycle were also found, such as L. ferrooxidans, A. ferrooxidans, and Acidocella sp. Similar studies performed in other extreme environments, such as acidic hot-spring sediments, the Tinto River and acid mine drainage-affected areas were reported (Alazar et al., 2010; Rowe et al., 2007; Sánchez-Andrea et al., 2012a, 2013; Willis et al., 2013).
Recycling of Electronic Waste
Published in Hong Hocheng, Mital Chakankar, Umesh Jadhav, Biohydrometallurgical Recycling of Metals from Industrial Wastes, 2017
Hong Hocheng, Mital Chakankar, Umesh Jadhav
Taking into account the importance of H+ consumption during bioleaching and to analyze the leaching mechanism, Yang et al. (2014) investigated the kinetics of metal recovery and the relationship between H+ consumption and metal recovery from WPCBs using At. ferrooxidans. The bioleaching efficiency decreased rapidly as the WPCB concentration increased from 15 to 35 g/L. When the WPCB concentration was 15 g/L, Cu (96.8%), Zn (83.8%), and Al (75.4%) were recovered after 72 h by At. ferrooxidans. Experimental results indicated that the metal recovery rate was significantly influenced by acid. In the bioleaching process, metal recovery is related to the metal’s reactivity, and the stronger the metal’s reactivity, the faster and easier the bioleaching. In addition, the alkaline substance of WPCBs (direct consumption) and the oxidation reaction of Fe2+ (indirect consumption) consume H+. Thus, adding acid can maintain the pH of the leaching solution and contribute to improving the leaching efficiency indirectly by ensuring that the iron cycle proceeds well. Moreover, the bioleaching kinetics of metals fits the second-order model (with the addition of acid) well. However, the kinetics would change from the second-order model to the shrinking-core model because the amount of precipitate increases with time (without the addition of acid).
Effect of hydraulic retention time, ZVI concentration, and Fe2+ concentration on autotrophic denitrification efficiency with iron cycle bacterium strain CC76
Published in Environmental Technology, 2021
Jun feng Su, Xiao fen Hu, Ting ting Lian, Li Wei
In this work, we isolated a new type of efficient reducing iron Enterobacter sp.CC76. At the same time, we proposed a way for CC76 to remove nitrate through iron cycle. We studied the nitrate removal capacity of strain CC76 in the iron reduction bacteria immobilization reactor and the zero-valent iron immobilization system was verified by different hydraulic retention time, the amount of ZVI, and the amount of Fe2+. Also, we analysed optimal removal conditions. Furthermore, high-throughput sequencing analysis was used to study microbial community structure and dominant species.
The treatment of high-concentration garlic processing wastewater by UASB-SBR
Published in Environmental Technology, 2023
Wei Li, Xinyu Zhu, Yunhe Hou, Yuqi Wang, Yiming Chen, He Wang
In this experiment, Planctomycetes, Bacteroidetes, Candidatus Saccharibacteria and Actinobacteria gradually became the main bacteria phyla during the operation of the reactor and played their respective roles in pollutants removal. The microbial distribution at the phylum level in SBR was similar to that in other water treatment systems. Bacteroidetes and Proteobacteria were significant and common bacteria in wastewater treatment systems, known for having organic degradation, denitrification and phosphorus removal capabilities [38–40]. In addition, Actinobacteria could contribute to denitrification during anaerobic conditions, and Acidobacteriota had been proved to be related to the iron cycle and able to reduce iron under anaerobic conditions. Candidatus Saccharibacteria was also a dominant phylum in SBR, mainly for organic degradation [41,42]. As shown in Figure 11, comparing H1 and H2, the proportion of Candidatus Saccharibacteria had gradually increased from 0.66% to 24.05%. On the contrary, Proteobacteria, Bacteroidetes and Planctomycetes had decreased, elucidating that the high-concentration wastewater was beneficial to the growth of Candidatus Saccharibacteria, and harmful to the growth of others. The proportion of Proteobacteria, Bacteroidetes and Actinobacteria in H3 was more than those in H2. Among them, Actinobacteria was the most significant, ranging from 1.72% to 18.04%, illustrating that the natural culture method was more beneficial to the growth of Actinobacteria. The proportion of Candidatus Saccharibacteria in the inoculated sludge system was significantly higher than that in the natural culture system. It indicated that the natural culture method of activated sludge was not conducive to the growth of the Candidatus Saccharibacteria and reflected the difference between the two culture domestication methods in the microbial structure.
Treatment of textile matrices using Fenton processes: influence of operational parameters on degradation kinetics, ecotoxicity evaluation and application in real wastewater
Published in Journal of Environmental Science and Health, Part A, 2021
Rayany Magali da Rocha Santana, Daniella Carla Napoleão, Marta Maria Menezes Bezerra Duarte
According to researchers,[34] Fe3+ complexes formed from Fe2+ oxidation in the first step of reaction are capable to absorb photons. Then, these ions are reduced to Fe2+ complexes, restarting the iron cycle. Therefore, there is a continuous production of active oxidizing radicals, which are available to degrade pollutant molecules. Regarding the dye concentration decay through the processes, the kinetic monitoring was performed for both λ (Figure 2).