Anaerobic Biodegradation of Blends Based on Polyvinyl Alcohol

The presented work deals with blends composed of polyvinyl alcohol (PVA) and biopolymers (protein hydrolysate, starch, lignin). PVA does not belong to biologically inert plastics but its degradation rate (particularly under anaerobic conditions) is low. A potential solution to the issue problem lies in preparation of blends with readily degradable substrates. We studied degradation of blow-molded films made of commercial PVA and mentioned biopolymers in an aqueous anaerobic environment employing inoculation with digested activated sludge from the municipal wastewater treatment plant. Films prepared in the first experimental series were to be used for comparing biodegradation of blends modified with native or plasticized starch; in this case effect of plasticization was not proved. The degree of PVA degradation after modification with native or plasticized starch increases in a striking and practically same manner already at a starch level as low as approximately 5 wt.%. Films of the second experimental series were prepared as additionally modified with protein hydrolysate and lignin. Only lignin-modified samples exhibited a somewhat lower degree of biodegradation but regarding the measure of lignin present in blend this circumstance is not essential. Level of biodegradation with all discussed films differed only slightly—within range of experimental error.     

Analysis of emergency situations at municipal solid waste landfills

Journal of Material Cycles and Waste Management - This work focuses on the issue of emergency prevention in the operation of municipal solid waste landfills. In this work, an emergency is...     

A side-by-side comparison of two systems of sequencing coupled reactors for anaerobic digestion of the organic fraction of municipal solid waste.

The objective of this work was to compare the performance of two laboratory-scale, mesophilic systems aiming at the anaerobic digestion of the organic fraction of municipal solid wastes (OFMSW). The first system consisted of two coupled reactors packed with OFMSW (PBR1.1-PBR1.2) and the second system consisted of an upflow anaerobic sludge bed reactor (UASB) coupled to a packed reactor (UASB2.1-PBR2.2). For the start-up phase, both reactors PBR 1.1 and the UASB 2.1 (also called leading reactors) were inoculated with a mixture of non-anaerobic inocula and worked with leachate and effluent full recirculation, respectively. Once a full methanogenic regime was achieved in the leading reactors, their effluents were fed to the fresh-packed reactors PBR1.2 and PBR2.2, respectively. The leading PBR 1.1 reached its full methanogenic regime after 118 days (Tm, time to achieve methanogenesis) whereas the other leading UASB 2.1 reactor reached its full methanogenesis regime after only 34 days. After coupling the leading reactors to the corresponding packed reactors, it was found that both coupled anaerobic systems showed similar performances regarding the degradation of the OFMSW. Removal efficiencies of volatile solids and cellulose and the methane pseudo-yield were 85.95%, 80.88% and 0.109 NL CH4 g(-1) VS(fed) in the PBR-PBR system; and 88.75%, 82.61% and 0.115 NL CH4 g(-1) VS(fed0 in the UASB-PBR system [NL, normalized litre (273 degrees K, 1 ata basis)]. Yet, the second system UASB-PBR system showed a faster overall start-up.     

Michoacán centre for science and technology education a summary of the project

Summary This paper looks at the problems of science and technology education in Mexico, and proposes ways in which the quality of education at every level can be improved. It advocates an interdisciplinary approach, and from that approach to science education, the development of environmental education.Prof. Gutiérrez-Vázquez received his training in microbiology and biochemistry in the National Polytechnic Institute in his native Mexico City, receiving his degree in 1954. He went from instructor to assistant professor (1950–1960), becoming a full professor, deputy dean and then dean of the Faculty of Biology in the same Institute (1961–1969); he published two books and some 20 papers dealing with the physiology of tubercle bacillus and other mycobacteria, as well as with other topics on microbiology. More recently (1970 to date), he became a full professor in the Center for Advanced Studies of the same Institute, where he has been head of the Department of Educational Research (1972–1981) and carried out research and development projects on science education for children and adolescents. During this period he has published some 20 more books and 30 odd papers, and written more than 80 science programmes for commercial television.     

Colonization of surfaces by phenolic compounds utilizing microorganisms

The aim of the present study is to determine optimal adhesive interaction of phenolic compounds utilizing Candida maltosa and Rhodococcus erythropolis when adhering to kaolin, silicone, synthetic foil (Steriking R40) and fluorinated silicones, comparing cell and support surface hydrophobicity. In parallel, the interfering effect of detergents was investigated. Data obtained show that the less hydrophobic supports display high initial cell adhesion when contacted with the cell type with a lower surface hydrophobicity (yeast cell) but most stable yeast biofilms are those formed on highly hydrophobic fluorinated silicones. On the other hand, support hydrophobicity has no effect on bacterial cell detachment; however, bacterial biofilms are denser when growing on more hydrophobic supports. Both detergents interfere (independently on the cell type) with the early and late phases of biofilm development.     

Economic Underdevelopment And Sustainable Development In The World:Conditioning Factors,Problems And Opportunities

This paper deals with the various factors that condition underdevelopment in the world. It suggests some alternatives and points out the potential opportunities that both the developed and the underdeveloped world will have in the coming years to change the gloomy prospects that we see today. The present paper outlines the trends in historical priorities in development, changing as they pass from economic development to social development to ecological conservation – the three pillars of Sustainable Development.The paper analyses the importance of geography, a very relevant and often neglected conditioning factor. Also, it analyses the role of socio-economic conditioning factors like political immaturity, demographics, land ownership and external debt.Furthermore, the current opportunities for economic take-off are presented, from cash surpluses to low interest rates, from natural resource management to tourism or migration, from the Information Revolution to liberalisation of agricultural markets. Current obstacles are also analysed. The paper, on the basis of current facts and figures, reaches the conclusion that there is a structural need for sustained development aid for most poor countries, but it must be distributed in a more rational way.Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.