Waste plastics recycling by an entrained-flow gasifier

We studied an entrained-flow gasification process which efficiently converts waste plastics to energy at a high energy recovery rate. Waste plastics, after being shredded to <8 mm or <14 mm, were fed into an entrained-flow gasifier with air and oxygen. In the gasifier, organic substances were pyrolyzed, partially combusted, and then converted into synthetic gas (CO, H₂) at a high temperature (over 1600 K). The clarified gasification characteristics were that the lower heat value (LHV) of the product gas was over 4.2 MJ/Nm³ and the cold gas efficiency was approximately 60%. Other inert substances in the wastes such as ashes and metals were melted into slag and condensed on bag filters. The bag filters and a water scrubber removed impurities such as dusts, heavy metals, and hydrogen halides from the product gases. Solid hydrocarbons, which include char and soot, were removed at a hot cyclone and on the bag filters. Received: July 19, 2000 / Accepted: October 3, 2000     

Dietary contribution of the microphytobenthos to infaunal deposit feeders in an estuarine mudflat in Japan

The food sources of benthic deposit feeders were investigated at three stations in an estuarine mudflat (Idoura Lagoon, Sendai Bay, Japan) during July and August 2005, using δ¹³C and δ¹⁵N ratios. Sediment at the stations was characterized by low chlorophyll (chl) a content (0–1 cm depth, <4 μg cm⁻²) and the dominance of riverine–terrestrial materials (RTM) in the sediment organic matter (SOM) pool. Surface-deposit feeders (Macoma contabulata, Macrophthalmus japonicus, and Cyathura muromiensis) exhibited much higher δ¹³C values (−18.4 to −12.4‰) than did the SOM pool (<−25‰). A δ¹³C-based isotopic mixing model estimated that benthic diatoms comprised 45–100% (on average) of their assimilated diet, whereas RTM comprised a lesser fraction (29% maximum). The major diet of the deep-deposit feeding polychaetes Notomastus sp. and Heteromastus sp. was benthic diatoms and/or marine particulate organic matter (POM), with little RTM assimilated (39% maximum). The consumers appeared to lack specific digestive enzymes and to use detritus-derived carbon only after its transfer to the microbial biomass. The isotopic mixing model also showed that the dietary contribution of RTM increased slightly (15% maximum) in the vicinity of freshwater input, suggesting that spatial changes in RTM supply affect the dietary composition of deposit feeders. These results clearly demonstrate that deposit feeders selectively ingest and/or assimilate the more nutritious microalgal fractions in the SOM pool. Such adaptations may allow enhanced energy gain in estuarine mudflats that are rich in vascular plant detritus with low nutritive value.     

Fitness of occupational exposure data to inverse Gaussian distribution

Short-term exposure datasets of 10 workers exposed to organic solvents and daily average exposure datasets of seven workers exposed to cobalt and organic solvents were analyzed in order to clarify whether these exposure data fit an inverse Gaussian distribution. The goodness-of-fit test showed that time-weighted average (TWA) values with averaging times of 30 min, 60 min and 8 hours can be described by an inverse Gaussian distribution, but not those with averaging times of 7.5 min and 15 min.     

Novel metabolic pathways of organochlorine pesticides dieldrin and aldrin by the white rot fungi of the genus Phlebia

White rot fungi can degrade a wide spectrum of recalcitrant organic pollutants, including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated biphenyls (PCBs). In this experiment, 20 white rot fungi, belonging to genus Phlebia, were investigated for their ability to degrade dieldrin. Based on the screening results, we further investigated Phlebia acanthocystis, Phlebia brevispora, and Phlebia aurea to determine their degradation capacity and metabolic products towards dieldrin and aldrin. The three fungi were able to remove over 50% of dieldrin in a low nitrogen medium, after 42 d of incubation. Three hydroxylated products were detected as metabolites of dieldrin, suggesting that in Phlebia strains, hydroxylation reactions might play an important role in the metabolism of dieldrin. In contrast to dieldrin, aldrin exhibited higher levels of degradation activity. Over 90% of aldrin was removed after 28 d of incubation, and several new metabolites of aldrin in microorganisms, including 9-hydroxyaldrin and two carboxylic acid products, were detected in fungal cultures. These results indicate that the methylene moiety of aldrin and dieldrin molecules might be prone to enzymatic attack by white rot fungi. In this study, we describe for the first time a new metabolic pathway of both compounds by fungi of genus Phlebia.     

Perfluorooctanesulfonate and perfluorooctanoate in raw and treated tap water from Osaka, Japan

Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) have been recognized as emerging environmental pollutants because of their ubiquitous occurrence in the environment, biota, and humans. PFOS and PFOA have been detected in water in Japan. Nevertheless, occurrence of PFOS and PFOA in potable water from municipal water treatment plants is not clearly known. We analyzed PFOS and PFOA in raw and tap water samples collected from 14 drinking water treatment plants in winter and summer seasons in Osaka to determine the concentrations of PFOS and PFOA in raw and potable tap water samples. PFOS and PFOA were detected in all raw water samples. Concentration ranges of PFOS and PFOA in raw water were 0.26-22 ng/l and 5.2-92 ng/l, respectively. Whereas the concentrations PFOS in raw water from Osaka were similar to those in other areas in Japan, the concentrations of PFOA were higher than in other areas. Concentration ranges of PFOS and PFOA in potable tap water were 0.16-22 ng/l and 2.3-84 ng/l, respectively. There were positive correlations between PFC concentrations in raw water and tap water samples. Therefore, the removal efficiency of PFCs by the present water treatment may be low. Based on the current action value reported by U.S. Environmental Protection Agency, PFOA concentrations found in tap water in Osaka is not expected to pose health risks.     

Exoenzymes of Trametes versicolor can metabolize coplanar PCB congeners and hydroxy PCB

Two fractions containing the oxidase activity toward 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) were obtained using ion-exchange DEAE-Sepharose column chromatography of the culture fluid of white-rot fungus, Trametes versicolor. These two fractions can reduce the level of coplanar PCB congeners (Co-PCBs). The ABTS oxidase in the first fraction passed through the DEAE-Sepharose column. The ABTS oxidase in the second fraction was adsorbed to the column at 相似文献