Bioremediation of oil-contaminated soil using Candida catenulata and food waste

Even though petroleum-degrading microorganisms are widely distributed in soil and water, they may not be present in sufficient numbers to achieve contaminant remediation. In such cases, it may be useful to inoculate the polluted area with highly effective petroleum-degrading microbial strains to augment the exiting ones. In order to identify a microbial strain for bioaugmentation of oil-contaminated soil, we isolated a microbial strain with high emulsification and petroleum hydrocarbon degradation efficiency of diesel fuel in culture. The efficacy of the isolated microbial strain, identified as Candida catenulata CM1, was further evaluated during composting of a mixture containing 23% food waste and 77% diesel-contaminated soil including 2% (w/w) diesel. After 13 days of composting, 84% of the initial petroleum hydrocarbon was degraded in composting mixes containing a powdered form of CM1 (CM1-solid), compared with 48% of removal ratio in control reactor without inoculum. This finding suggests that CM1 is a viable microbial strain for bioremediation of oil-contaminated soil with food waste through composting processes.     

Photodechlorination of octachlorodibenzothiophene and octachlorodibenzofuran: comparison of experimental degradation pathways with degradation pathways predicted by DFT

Polychlorodibenzothiophenes (PCDTs) are sulfur analogues of polychlorodibenzofurans (PCDFs) and have been detected in environmental samples. We used density functional theory calculations (Gaussian 98W) to predict the photodechlorination pathways of octachlorodibenzothiophene (OCDT) and octachlorodibenzofuran (OCDF) in hexane, and we compared the predicted pathways with those observed during UV irradiation experiments. OCDT and OCDF were observed to degrade through first-order dechlorination processes, and the rate constant for OCDT was less than one-third that for OCDF. The main experimental photodechlorination pathways of OCDT and OCDF led to hexachlorinated and tetrachlorinated congeners, respectively; that is, the photodechlorination pathway of OCDT differed from that of OCDF. On the assumption that the dechlorination mechanisms involved radical reactions, we used DFT calculations to estimate bond-dissociation energies and single-point energies of OCDT and OCDF and their dechlorinated congeners, and we used the resulting information, along with hypotheses regarding the rate-controlling step of the degradations, to predict theoretical degradation pathways. We propose that reaction of dechlorinated radicals with a hydrogen donor was the rate-controlling step for OCDT and that C-Cl bond dissociation by UV light was the rate-controlling step for OCDF.     

Trace metal contamination in commercial fish and crustaceans collected from coastal area of Bangladesh and health risk assessment

Environmental Science and Pollution Research - Trace metals contamination in commercial fish and crustaceans have become a great problem in Bangladesh. This study was conducted to determine seven...     

Gas reforming and tar decomposition performance of nickel oxide (NiO)/SBA-15 catalyst in gasification of woody biomass

In the gasification of biomass, it is necessary to limit the amount of by-product tar and increase the yields of hydrogen (H₂) and carbon monoxide (CO) (syngas). Therefore, we conducted gasification and reforming experiments on woody biomass using an electric tubular furnace, to evaluate the gas reforming and tar decomposition performance of a NiO/SBA-15 catalyst. As a result, we found that this catalyst is effective for H₂ production. It is believed that the increase in H₂ volume due to the catalyst occurs through a steam reforming reaction involving hydrocarbons, including methane (CH₄), and the water-gas shift reaction. With respect to the influence of the gasifying agent on the reforming effect of the catalyst, the amount of generated carbon dioxide (CO₂) and hydrogen (H₂) increases because the shift reaction is promoted by supplying steam. On the other hand, it was inferred that the shift reaction rarely occurred because it approaches equilibrium by supplying O₂. Furthermore, it is suggested that light aromatic hydrocarbons are decomposed by the catalyst.

Implications: The mesoporous silica catalyst NiO/SBA-15 was highly effective for H₂ production and decomposition of light aromatic compounds in the gasification of woody biomass. In the catalyst reaction, supplying steam promoted H₂ production. From thermodynamic analysis and discussion, it was also inferred that supplying O₂ might prevent the water gas shift reaction. The results are useful for designing a process needed for rich H₂ production and gas refining process for further use of syngas.     

Identification of microbial populations contributing to nitrification-associated nitrous oxide emission during cattle manure composting process with forced aeration

Journal of Material Cycles and Waste Management - This study was conducted to clarify the fates of whole nitrogen cycle-associated microorganisms during laboratory-scale composting of cattle manure...     

Analyzing flood risk and related impacts to urban communities in central Vietnam

This study aims at understanding flood risks and their impact on a community, in order to enhance communities’ resilience and adaptive capacity to these threats. It also investigates the possibility of looking at and handling risk from a resilience point of view. Therefore, while a conventional risk management process is employed in this study, social, physical, economic, and institutional dimensions of resilience are also included in order to grasp the extent of risks and the ways in which communities face, cope with, and recover from flooding. Findings showed that there was no significant difference in the perception of flood risk among household heads educated up to secondary school level, suggesting that they believe floods are purely natural events. Those with a higher level of education (high school and above) (82.7 % of respondents) were aware that flood disasters are the result of hazard and vulnerability combined. In addition, social dynamics were apparently strengthened by such disasters, which resulted in cohesion and mutual help following floods in some wards. Also, households with more sources of income and more savings appear to recover faster than others after a flooding event. With regard to governance and networks, greater efforts have to be made by local institutions to ensure basic functioning during and after disaster events and to invest more into risk reduction activities. However, further studies need to be conducted to clarify the understanding of the impact flood disasters have on the environment and community lives and livelihoods in general, as traditional coping strategies, although still practical, no longer suffice in the face of changes in climate and environment.     

Synthesis and characterizations of Zr(IV)-loaded orange waste for effective sequestration of Mo(VI) and W(VI) from water

Journal of Material Cycles and Waste Management - An efficient and environmentally benign biosorbent for Mo(VI) and W(VI) sequestration was developed by loading Zr(IV) ions onto Saponified Orange...     

Measurements of short-lived cosmic-ray-produced radionuclides in rainwater

Cosmic-ray-produced (CP) nuclides with half-lives shorter than 21h were measured in rainwater by ultra-low-background gamma spectrometry at Ogoya Underground Laboratory. As levels of CP nuclides are extremely low and their half-lives are very short, quick sampling methods for a large volume of rainwater and rapid chemical separations by ion exchange method were developed. The nuclides measured were short-lived (24)Na, (28)Mg, (38)S, (38)Cl, (39)Cl, as well as nuclides with longer half-lives (7)Be and (22)Na. The number of atoms of CP nuclides in rainwater were evaluated to range from 30 to 1500L(-1) for (24)Na (n=16, mean; 520 [6.7mBqL(-1)]), 80 to 600L(-1) for (28)Mg (n=13, mean; 260 [2.4mBqL(-1)]), 400 to 1900L(-1) for (39)Cl (n=6, mean; 1200 [250mBqL(-1)]), 1x10(6) to 4x10(7)L(-1) for (7)Be (n=16, mean; 7x10(6) [1.05BqL(-1)]) and 2x10(3) to 1x10(5)L(-1) for (22)Na (n=9, mean; 2x10(4) [0.2mBqL(-1)]).     

Decolorization of Orange II using an anaerobic sequencing batch reactor with and without co-substrates

We investigated the decolorization of Orange II with and without the addition of co-substrates and nutrients under an anaerobic sequencing batch reactor (ASBR). The increase in COD concentrations from 900 to 1750 to 3730 mg/L in the system treating 100 mg/L of Orange II-containing wastewater enhanced color removal from 27% to 81% to 89%, respectively. In the absence of co-substrates and nutrients, more than 95% of decolorization was achieved by the acclimatized anaerobic microbes in the bioreactor treating 600 mg/L of Orange II. The decrease in mixed liquor suspended solids concentration by endogenous lysis of biomass preserved a high reducing environment in the ASBR, which was important for the reduction of the Orange II azo bond that caused decolorization. The maximum decolorization rate in the ASBR was approximately 0.17 g/hr in the absence of co-substrates and nutrients.     

Bacterial community succession during the enrichment of chemolithoautotrophic arsenite oxidizing bacteria at high arsenic concentrations

To generate cost-effective technologies for the removal of arsenic from water, we developed an enrichment culture of chemolithoautotrophic arsenite oxidizing bacteria (CAOs) that could effectively oxidize widely ranging concentrations of As(III) to As(V). In addition, we attempted to elucidate the enrichment process and characterize the microbial composition of the enrichment culture. A CAOs enrichment culture capable of stably oxidizing As(III) to As(V) was successfully constructed through repeated batch cultivation for more than 700 days, during which time the initial As(III) concentrations were increased in a stepwise manner from 1 to 10-12 mmol/L. As(III) oxidation activity of the enrichment culture gradually improved, and 10-12 mmol/L As(III) was almost completely oxidized within four days. Terminal restriction fragment length polymorphism analysis showed that the dominant bacteria in the enrichment culture varied drastically during the enrichment process depending on the As(III) concentration. Isolation and characterization of bacteria in the enrichment culture revealed that the presence of multiple CAOs with various As(III) oxidation abilities enabled the culture to adapt to a wide range of As(III) concentrations. The CAOs enrichment culture constructed here may be useful for pretreatment of water from which arsenic is being removed.