Anaerobic biodegradation of ethylthionocarbamate by the mixed bacteria under various electron acceptor conditions

Effects of terminal electron acceptors on the biodegradation of waste motor oil using Chlorella vulgaris-Rhodococcus erythropolis consortia: Kinetic and thermodynamic windows of opportunity analysis

The Chlorella vulgaris-Rhodococcus erythropolis consortia was constructed for the biodegradation of waste motor oil (WMO), combined with thermodynamic calculations and stoichiometric analyses. The microalgae-bacteria consortium was constructed as C. vulgaris: R. erythropolis = 1:1 (biomass, cell/mL), pH = 7, 3 g/L WMO. Under the same condition, the terminal electron acceptors (TEAs) play a crucial role in the WMO biodegradation, which follows Fe3+ >SO42- > none. The biodegradation of WMO fitted well with the first-order kinetic model under experimental temperatures with different TEAs (R2 >0.98). The WMO biodegradation efficiency reached 99.2 % and 97.1 % with Fe3+ and SO42-as TEAs at 37 °C, respectively. Thermodynamic methanogenesis opportunity windows with Fe3+ as TEA are 2.72 times fold as large as those with SO42-. Microorganism metabolism equations demonstrated the viability of anabolism and catabolism on WMO. This work lays the groundwork for the implementation of WMO wastewater bioremediation and supports research into the biochemical process of WMO biotransformation.

Removal of Flotation Collector O-Isopropyl-N-ethylthionocarbamate from Wastewater

Flotation collector O-isopropyl N-ethylthionocarbamate (IPETC) is widely used for separation of sulfide ores. Its removal from water by several oxidation processes was studied. Photocatalytic oxidation with air in the presence of iron salts, utilizing solar irradiation or artificial UV-A light is very efficient. Oxidation leads through the formation of O-isopropyl N-ethylcarbamate and several other reaction intermediates to total decomposition of organic compound in the final stage in 1 day. Similar results were obtained with a Fenton type oxidation with hydrogen peroxide and iron salts. Treatment with sodium hypochlorite yields mainly O-isopropyl N-ethylcarbamate. The formation of this compound in wastewaters can be of concern, since simple alkyl carbamates are cancer suspect agents.

Anaerobic degradation of xenobiotic organic contaminants (XOCs): The role of electron flow and potential enhancing strategies

In groundwater, deep soil layer, sediment, the widespread of xenobiotic organic contaminants (XOCs) have been leading to the concern of human health and eco-environment safety, which calls for a better understanding on the fate and remediation of XOCs in anoxic matrices. In the absence of oxygen, bacteria utilize various oxidized substances, e.g. nitrate, sulphate, metallic (hydr)oxides, humic substance, as terminal electron acceptors (TEAs) to fuel anaerobic XOCs degradation. Although there have been increasing anaerobic biodegradation studies focusing on species identification, degrading pathways, community dynamics, systematic reviews on the underlying mechanism of anaerobic contaminants removal from the perspective of electron flow are limited. In this review, we provide the insight on anaerobic biodegradation from electrons aspect - electron production, transport, and consumption. The mechanism of the coupling between TEAs reduction and pollutants degradation is deconstructed in the level of community, pure culture, and cellular biochemistry. Hereby, relevant strategies to promote anaerobic biodegradation are proposed for guiding to an efficient XOCs bioremediation.

Vertically aligned Pt/TiO2 nanobelt films on Ti sheets for efficient degradation of a refractory ethyl thionocarbamate collector

Noble metal modified TiO2 nanostructures on a substrate featuring a two-dimensional (2D) morphology are of great interest in wastewater remediation due to high photocatalytic activity and avoidance of separating powder catalysts from water. In this work, vertically aligned Pt/TiO2 nanobelt films (Pt/TNFs) on Ti sheets were fabricated via a synthesis strategy including an alkaline hydrothermal treatment and electrostatic self-assembly. The Pt/TNFs had a BET specific surface area of 93.35 m2 g-1, showing high adsorption capacity in removing an ethyl thionocarbamate (ETC) flotation collector. After the deposition with Pt nanoparticles, the photocatalytic activity of the TNFs increased by 94.98% with the enhanced mineralization of the ETC collector. Moreover, the Pt/TNFs on Ti sheets exhibited strong substrate adhesion enabling superior photocatalytic stability in the cyclic degradation of ETC. The solid phase extraction and gas chromatography-mass spectrometry (SPE/GC-MS) analysis revealed that seven byproducts still remained even when 100% of ETC was degraded, showing the difficulty in the complete mineralization of the ETC collector. The Pt/TNF can serve as a promising photocatalyst to treat mineral flotation wastewaters containing organic reagents.

Efficient natural pyrrhotite activating persulfate for the degradation of O-isopropyl-N-ethyl thionocarbamate: Iron recycle mechanism and degradation pathway

Natural pyrrhotite (NP) shows promising future in activating persulfate (PS) due to its easy availability at a low cost and easy separation. This study discussed the degradation of O-isopropyl-N-ethyl thionocarbamate (IPETC) in NP/PS system. NP-PS system showed the best IPETC mineralization at the initial pH of 6.0 (62.84%). The kinetics study suggested that the IPETC degradation followed the pseudo-first-order equation in the NP-PS system. NP-PS system worked better in bottled water (96.46%) and tap water (85.14%) than river water (31.28%). Combined with Fourier transform-infrared spectroscopy, gas chromatography-mass spectrometry and computational calculation, the degradation products, including acetone, formic acid isopropyl ester and ethylamine, were identified and the degradation pathway of IPETC in NP-PS system was proposed. The S, O and N atoms in IPETC are easier to be attacked by. SO₄^-Ethylamine and reduced S ions coordinately worked to recycle Fe²⁺ in NP/PS/IPETC system.

Combined effects of antimony and sodium diethyldithiocarbamate on soil microbial activity and speciation change of heavy metals. Implications for contaminated lands hazardous material pollution in nonferrous metal mining areas

The combined effects of antimony (Sb) and sodium diethyldithiocarbamate (DDTC), a common organic flotation reagent, on soil microbial activity and speciation changes of heavy metals were investigated for the first time. The results showed that the exchangeable fraction of Sb was transformed to a stable residual fraction during the incubation period, and the addition of DDTC promoted the transformation compared with single Sb pollution, probably because DDTC can react with heavy metals to form a complex. In addition, the presence of DDTC and Sb inhibited the soil microbial activity to varying degrees. The growth rate constant k of different interaction systems was in the following order on the 28th day: control group ≥ single DDTC pollution > combined pollution > single Sb pollution. A correlation analysis showed that the concentration of exchangeable Sb was the primary factor that affected the toxic reaction under combined pollution conditions, and it significantly affected the characteristics of the soil microorganisms. All the observations provide useful information for a better understanding of the toxic effects and potential risks of combined Sb and DDTC pollution in antimony mining areas.

Effects of different electron acceptors on the methanogenesis of hydrolyzed polyacrylamide biodegradation in anaerobic activated sludge systems

The type of electron acceptor was a crucial factor in regulating the methanogenic process of anaerobic hydrolyzed polyacrylamide (HPAM) degradation. The combined methods of biodegradation experiments and thermodynamic calculations were applied to explore the effects of different electron acceptors on methanogenic HPAM degradation. Under the conditions of without electron acceptor, SO₄^2-, Fe³⁺, SO₄^2- and Fe³⁺ as electron acceptors, HPAM biodegradation ratio reached 31.56%, 41.48%, 49.4% and 61.1%, acetate production reached 0.0532, 28.28, 112.7 and 141.95mg·L^-1, CH₄ production reached 0.024, 0.3015, 9.446 and 11.78mg·L^-1, respectively. The synergistic effect of SO₄^2- and Fe³⁺ further promoted methanogenic HPAM biotransformation. Archaeal community analysis revealed that Methanobacteriales, Methanomicrobiales and Methanosarcinales were dominant. Thermodynamic opportunity windows of methanogenesis with Fe³⁺ as electron acceptor are 35 times larger than that with SO₄^2- as electron acceptor. It indicated that acetoclastic methanogenesis was dominant and hydrogenotrophic methanogenesis was inhibited in the methane-producing process of anaerobic HPAM degradation.

Degradation of dichloromethane by an isolated strain Pandoraea pnomenusa and its performance in a biotrickling filter

A strain Pandoraea pnomenusa LX-1 that uses dichloromethane (DCM) as sole carbon and energy source has been isolated and identified in our laboratory. The optimum aerobic biodegradation of DCM in batch culture was evaluated by response surface methodology. Maximum biodegradation (5.35 mg/(L·hr)) was achieved under cultivation at 32.8°C, pH 7.3, and 0.66% NaCl. The growth and biodegradation processes were well fitted by Haldane's kinetic model, yielding maximum specific growth and degradation rates of 0.133 hr(-1) and 0.856 hr(-1), respectively. The microorganism efficiently degraded a mixture of DCM and coexisting components (benzene, toluene and chlorobenzene). The carbon recovery (52.80%-94.59%) indicated that the targets were predominantly mineralized and incorporated into cell materials. Electron acceptors increased the DCM biodegradation rate in the following order: mixed > oxygen > iron > sulfate > nitrate. The highest dechlorination rate was 0.365 mg Cl(-)/(hr·mg biomass), obtained in the presence of mixed electron acceptors. Removal was achieved in a continuous biotrickling filter at 56%-85% efficiency, with a mineralization rate of 75.2%. Molecular biology techniques revealed the predominant strain as P. pnomenusa LX-1. These results clearly demonstrated the effectiveness of strain LX-1 in treating DCM-containing industrial effluents. As such, the strain is a strong candidate for remediation of DCM coexisting with other organic compounds.