Benzene removal with vertical‐flow constructed treatment wetlands

BACKGROUND: Twelve vertical‐flow experimental wetlands have been constructed using different compositions, and were operated in batch‐flow mode to reduce pumping costs. Six wetlands were located indoors and six outdoors. Benzene was used as a representative example substance to assess the removal of low molecular weight petroleum compounds. RESULTS: Findings indicate that the constructed wetlands remove benzene (inflow of approximately 1.3 g L^?1) from hydrocarbon‐contaminated wastewater streams with better indoor (controlled environment) than outdoor treatment performances. Overall mean removal efficiencies for the experimental rig placed outside were as follows: benzene 85%, chemical oxygen demand (COD), 70%; ammonia‐nitrogen, 83%; nitrate‐nitrogen, 88%; ortho‐phosphate‐phosphorus, 58%. In comparison, removal efficiencies for the experimental rig placed indoors were higher: benzene 95%, COD, 80%; ammonia‐nitrogen, 90%; nitrate‐nitrogen, 94%; ortho‐phosphate‐phosphorus, 66%. Benzene removal was predominantly due to volatilization after 1 day of retention time. CONCLUSION: The use of aggregates (sand and gravel) and the presence of Phragmites australis (Cav.) Trin. ex Steud. resulted in no significant difference in terms of benzene, redox potential, dissolved oxygen, 5‐day at 20 °C N‐allylthiourea biochemical oxygen demand, COD and nutrients removal. Statistical differences were assessed by analysis of variance and Tukey HSD tests (P < 0.05). Copyright © 2007 Society of Chemical Industry     

Poly(L-lactide)-degrading activity of a newly isolated bacterium

A new strain exhibiting poly(L -lactic acid) (PLLA)-degrading activity was isolated from the compost loaded with low-molecular weight PLLA. The strain was rod-shaped gram positive bacterium and was identified to be Bacillus licheniformis by the 16S rDNA sequence analysis. It degraded not only low-molecular weight PLLA but also other PLLAs having higher molecular weight. The lower the molecular weight of PLLA, the faster the biodegradation rate. And thereby 45% and 81% of PLLAs with weight average molecular weight of 256,000 and 5,000, respectively, were metabolized into CO₂ after 40 days of biodegradation at 58°C in the sterilized compost inoculated with the bacterium. According to the 16S rDNA sequence analysis, B. licheniformis PLLA-2 belonged to Bacillus spp. phylogenetically. However, there existed almost no phylogenetic relationship between B. licheniformis PLLA-2 and the previously reported PLLA-degrading strains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Formaldehyde biodegradation in the presence of methanol under denitrifying conditions

Simultaneous formaldehyde and methanol biodegradation and also denitrification were studied in batch assays and in a continuous laboratory‐scale reactor. In batch assays, high formaldehyde concentrations (up to 1360 mg dm^?3) were removed under anoxic conditions in the presence of methanol. It was found that formaldehyde biodegradation produced methanol and formic acid as products. The denitrification process was affected by the initial formaldehyde concentration. In the continuous reactor, the biodegradation of different concentrations of formaldehyde (1500–275 mg dm^?3) and methanol (153–871 mg dm^?3) took place, maintaining the organic loading rate at 0.84 g COD dm^?3 d^?1 (COD/N 4). However, each increase in the methanol concentration in the influent caused a decrease in the denitrification level. An adaptation period to methanol was necessary before the denitrification percentage could be recovered. In contrast with batch assays, in the continuous reactor methanol and formic acid were not detected in the effluent. Moreover, in the continuous reactor the denitrification percentages were higher and the nitrite accumulation was lower. Copyright © 2005 Society of Chemical Industry     

淀粉——聚乙烯降解体系的分析与设计

研究了淀粉-聚乙烯降解体系中相容剂、增塑剂对材料力学性能的影响,分析了淀粉的填料特性以及与普通无机填料的区别,讨论了淀粉在加工过程中发生的变化,为得到较高机械性能的淀粉-聚乙烯降解材料提供了途径。     

Thermally treated low density polyethylene biodegradation by Penicillium pinophilum and Aspergillus niger

Differential scanning calorimetry (DSC), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to determine morphological, structural and surface changes (biodegradation) on thermo‐oxidized (80°C, 15 days) low‐density polyethylene (TO‐LDPE) incubated with Aspergillus niger and Penicillium pinophilum fungi, with and without ethanol as cosubstrate for 31 months. TO‐LDPE mineralization by fungi was also evaluated. Significantly morphological and structural final changes on biologically treated TO‐LDPE samples were observed. Decreases to three units on crystallinity and crystalline lamellar thickness (0.4–1.8 Å), and increases in small‐crystals content (up to 3.2%) and mean crystallite size (8.4–14 Å) were registered. An oxidation decrease (almost twice) on samples without ethanol with respect to the control was observed, while in those with ethanol it was increased (up to 2.5 times). Double bond index increased more than twice from 21 to 31 months. The higher TO‐LDPE changes and fungi‐LDPE interaction was observed in samples with ethanol, suggesting that ethanol favors the TO‐LDPE biodegradation, at least in case of P. pinophilum, probably by means of a cometabolic process. Mineralization of 0.50 % and 0.57 % for A. niger, and of 0.64 % and 0.37 % for P. pinophilum were obtained, for samples with and without ethanol, respectively. A model to explain morphological and structural changes on biologically treated TO‐LDPE is also proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 305–314, 2002     

竹纤维/聚己内酯复合化的研究

探讨了竹纤维／聚己内酯复舍化的方法，调制了相溶剂，通过在聚己内酯中添加不同比例的竹纤维和一定量的相溶剂，制成了竹纤维／聚己内酯复合材料．测试分析认为，添加竹纤维使复合材料拉伸强度先下降，后升高，使伸长率从大于900％下降至15％左右；相溶剂的添加提高了复合材料的耐水性和热稳定性．     

磁性生物陶瓷降解机理的研究

采用生理盐水对磁性生物陶瓷进行了体外模拟实验，并进行了相关的动物实验。对侵蚀后的材料的抗折强度、饱和磁矩及浸液进行了分析与测试。根据实验结果分析了影响磁性生物材料降解的因素并探讨了其降解机理。     

SP 淀粉塑料膜的制造、性能与应用

本文介绍了 ST/PVA 淀粉塑料薄膜的制造、性能和应用情况,该薄膜是当今世界新型高分子材料之一,具有原料丰富,成本较低和可自然降解无污染的特点,为解决塑料污染全球性问题提供一条可靠途径,属国内首创产品,有良好的开发前景。     

生物降解处理地下有机污染物的模型研究

本文综合多学科的研究结果，阐明了多孔介质中有机污染物和细菌微生物运动的形式，规律及其相互作用。采用二重孔隙介质模型，给出在裂隙含水层中建立其运动方程组与推导孔隙及裂隙交界面上交换关系的原则。以好氧菌及厌氧菌共存系统为例，得出具体的控制方程系统和交换关系式，并进行了数值模拟，得到了有用的结果。     

The specificity and the ability of Aspergillus feruloyl esterase to release p‐coumaric acid from complex cell walls of oat hulls

p‐Coumaric acid (4‐hydroxycinnamic) and ferulic acid (4‐hydroxy‐3‐methoxycinnamic), two major hydroxycinnamic acids found in the complex cell walls of oat hulls, act as cross‐linking agents between lignin and polysaccharides or between polysaccharides. As such, they are inhibitory to the biodegradation of cell walls by microorganisms. A previous study showed that Aspergillus feruloyl esterase with Trichoderma xylanase was able to break the ester linkage between ferulic acid and the attached sugar, releasing ferulic acid from the cell wall. The objective of this study was to investigate the specificity and the ability of Aspergillus feruloyl esterase to release p‐coumaric acid from oat hulls. The results show there was no extensive release of p‐coumaric acid in both the absence and presence of Trichoderma xylanase by Aspergillus feruloyl esterase. This indicates a specificity of Aspergillus feruloyl esterase, which is more active only on esters of certain hydroxycinnamic acids; in this case, Aspergillus feruloyl esterase will only sufficiently break the ester‐linked feruloyl group but not the p‐coumaroyl group in the complex cell walls of oat hulls. Copyright © 2004 Society of Chemical Industry