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Contaminant Removal Capabilities of Wetlands Constructed to Treat Coal Mine Drainage
Published in Gerald A. Moshiri, Constructed Wetlands for Water Quality Improvement, 2020
This buffering reaction is important in mine drainage treatment systems because it maintains circumneutral pH. The pH of the water influences both the mechanism and the kinetics of iron oxidation processes. For aerobic waters with pH values greater than 4, the removal of iron is limited by the oxidation process (Equation 4). At pH values greater than 6, abiotic oxidation processes dominate over bacterial oxidation processes, while at pH values below 5 the relationship is reversed.13 In natural systems, the kinetics of the abiotic mechanism under circumneutral conditions can be 5 to 10 times faster than the biological mechanism at lower pH.
Mercury Toxicity
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Mohammed H. Abu-Dieyeh, Kamal Usman, Haya Alduroobi, Mohammad Al-Ghouti
Biological oxidation of Hg (0) received the least attention in the biogeochemical cycle of mercury (Barkay et al., 2003). Bacterial oxidation was demonstrated to be facilitated by peroxidases, however, even when mutant strains of the enzyme were subjected, low level oxidation was observed and hence the suggestion that other bacterial oxidases exists (Smith et al., 1998). The same authors report high oxidation activity against mercury by soil bacteria, Streptomyces and Bacillus as a recurring event in the element’s environmental cycling.
Inhibitory Effect of Solvent Extractants on Growth and Metabolism of Acidophiles
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Roozbeh Saneie, Hadi Abdollahi, Seyed Ziaedin Shafaei, Amirhossein Mohammadzadeh
The assessments of τB (Figure 8) revealed a high positive inter-correlation between the OPC and pH for both cultures. Various researchers have reported that the presence of organic compounds hinders the metabolism of the microorganism and their interaction with energy sources (Jafari et al. 2019b, 2019c). At high concentrations, the possible adsorption of organic extractant on the surface of elemental sulfur might reduce the sulfur oxidation rate and production of sulfuric acid in the culture media (Equation (3)). The negative correlation between pH and ORP for mesophiles (τB = −0.615) and moderate thermophiles (τB = −0.649) is one of the best-known bacterial metabolism indicators. Bacterial oxidation of sulfur and ferrous iron simultaneously reduces the pH and increases the oxidation potential of the medium (Chen and Lin 2004; Panda et al. 2018). The strong negative correlation between OPC and bacterial count of mesophiles (τB = −0.819) and moderate thermophiles (τB = −0.877) indicates the toxicity of organic chemicals to acidophiles. Although the increase in OPC resulted in a decline in both cultures, mesophiles were more resistant to the presence of extractants at 0.2% v/v than moderate thermophiles. It has been reported that acidophiles that grow in the exposure of organic compounds become shortened and have an abnormal cytoplasmic membrane and cell walls (Liu et al. 2015). The disorder in the bacterial shape and structure can lengthen the duplication of cells. For both cultures, there is a positive correlation between Ca and pH. Also, the significant negative correlation between Ca and ORP can be justified by the fact that a higher number of active cells resulted in a faster bio-oxidation of sulfur and Fe2+, leading to a lower pH and higher ORP.