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In Situ Gentle Remediation Measures for Heavy Metal-Polluted Soils
Published in Norman Terry, Gary Bañuelos, of Contaminated Soil and Water, 2020
S.K. Gupta, T. Herren, K. Wenger, R. Krebs, T. Hari
Different microorganisms have the ability to immobilize heavy metals in soils (Summers, 1992; Frankenberger and Losi, 1995), and it was suggested to use this ability to immobilize metals through the management of specific microbial populations (Morel et al., 1997). Immobilization mediated by microorganisms has the advantage of being more selective in the binding of a unique heavy metal than that associated with synthetic chemical sorbents. Microorganisms are able to stabilize soils by concentrating heavy metals either in an active process, called bioaccumulation, or by uptake processes that do not require energy, called biosorption (Bolton and Gorby, 1995). Furthermore, microorganisms can influence heavy metal solubility by direct or indirect reduction. As an example, Cr(VI) (chromate, CrO4-2) is mobile and toxic, whereas the reduced form, Cr(III), is relatively nontoxic and nonmobile in the environment (Bolton and Gorby, 1995). Similar reactions which precipitate metals were reported for arsenic (As(III) to As(0)), uranium (U(VI) to U(IV)), or selenium (Se(VI) to Se(0)). Sulfate-reducing bacteria are capable of precipitating metals as metal sulfides (Farmer et al., 1995).
Acid Sulfate Soils: Formation
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Soils and Terrestrial Systems, 2020
Martin C. Rabenhorst, Delvin S. Fanning, Steven N. Burch
It is clear that in environments which provide a source of oxidizable carbon and sulfate and which are sufficiently saturated to enhance reducing conditions, sulfate reducing bacteria will generate sulfide. If reactive iron is present, then solid phase ferrous minerals will accumulate. This process of sulfidization[14] is shown schematically in Figure 3. The obvious settings for these processes are coastal marine and brackish environments, where sulfate is abundant. Under permanently submersed conditions, detrital carbon is added by flora and fauna to the sediment. In shallow water settings (<3 m) where various pedogenic processes are at work, these accumulated sediments have been recognized as subaqueous soils[15] and are classified to reflect the sulfide components.
Anoxic Prokaryotes
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
Dissimilatory sulfate-reducing bacteria are obligate anaerobes that use organic acids, alcohols, and hydrogen as donors of electrons and sulfate or other oxoanions of sulfur as acceptors of electrons, for example: CH3COOH+SO42−→2CO2+H2S+2OH−4H2+SO42−→H2S+2H2O+2OH−
Influence of the nutrition substrate concentration on sulfate reduction in denitrifying biofilter point of use
Published in Indian Chemical Engineer, 2023
Viktor Gevod, Ivan Borysov, Liliya Frolova, Akmaral Issayeva
According to equation (28), the dosage of ethanol in supplied water 125 mg/dm3 exceeds the amount (74 mg/dm3) required by the denitrifying bacteria. As a result, ethanol also becomes available to sulfate-reducing bacteria, whose colonies occupy the space after the settlements of denitrifying bacteria. Sulfate-reducing bacteria produce hydrogen sulfide by cleaving oxygen from sulfate ions for respiration. The equation of sulfate reduction with the participation of ethanol as an electron donor in this process has the form [20]: The amount of hydrogen sulfide released into the water in the sulfate reduction zone is proportional to the ethanol residues not consumed by denitrifying bacteria. When hydrogen sulfide-containing samples have exposed to atmospheric air, this gas evaporates. The driving force is the difference in concentrations (partial pressures) in the sample volume and the atmospheric air. The process accelerates by the convective transfer of dissolved hydrogen sulfide to the water-atmosphere interface during the mixing and purging samples with air.
Microbial induced calcite precipitation for self-healing of concrete: a review
Published in Journal of Sustainable Cement-Based Materials, 2023
Rishav Garg, Rajni Garg, Nnabuk Okon Eddy
Furthermore, this type of healing agent can protect steel reinforcement against corrosion, acting as an oxygen diffusion barrier, because aerobic bacteria consume oxygen in the metabolic conversion pathway [75]. The nitrate reducing bacteria namely Diaphorobacter nitroreducens, and Pseudomonas aeruginosa encapsulated with granular activated carbon, diatomaceous earth, and expanded clay have been found to exhibit better survival and inhibit the corrosion of steel at controlled pH conditions [62]. Reinforced concrete specimens containing Sporosarcina pasteurii and cured in the urea–calcium lactate medium showed improved corrosion resistance with increased electrical resistance than compared to concrete specimens without steel reinforcement as well those containing Bacillus subtilis. An increase of calcite sediments inside concrete pores was credited for both a reduction in porosity and an increase in conductivity [84]. Researchers found that a new bio-concrete made from anaerobic granular sludge showed great promise in reducing sewer corrosion. The sulfate reducing bacteria in the sludge promoted the sulfur cycle between aerobic and anaerobic sub-layers of the corrosion leading to a net reduction in biogenic sulfuric acid generation. Consequently, corrosion rate was almost decreased to half as compared in conventional samples [85].
Photocatalytic degradation of Congo Red by zinc sulfide quantum dots produced by anaerobic granular sludge
Published in Environmental Technology, 2022
Jaya Mary Jacob, Arindam Sinharoy, Piet N. L. Lens
Reactors treating sulfate rich waters develop biofilms containing sulfate reducing, acidogenic and acetogenic bacteria and methanogenic archae [5]. These microbial groups produce extracellular polymeric substances (EPS) around their cells that help them to attach to each other and form large aggregates [6]. Sulfate Reducing Bacteria (SRB) possess a unique anaerobic respiratory and metal reducing capacity [7]. Under anaerobic conditions, sulfate reducing bacteria couple the oxidation of organic compounds to sulfate reduction, during which sulfate is reduced to sulfide. In the presence of heavy metals, sulfides precipitate as metal sulfides [8]. The above prospect opens up an alternative to the chemical or physical approaches to produce metal sulfide quantum dots (QDs), along with the treatment of heavy metal contaminated waste water.