Temporary feeding shocks increase the productivity in a continuous biohydrogen-producing reactor

Continuous hydrogen production stability and robustness by dark fermentation were comprehensively studied at laboratory scale. Continuous bioreactors were operated at two different hydraulic retention times (HRT) of 6 and 10 h. The reactors were subjected to feeding shocks given by decreases in the HRT, and therefore the organic loading increases, during 6 and 24 h. Results indicated that the H₂ productivity was significantly improved by the temporary organic shock loads, increasing the hydrogen production rate up to 40%, compared to the rate obtained at the steady-state condition. Besides, it was observed that after the shock load, the stability of the reactor (measured as the hydrogen production rate) was recovered attaining the values observed before the feeding shocks. The bioreactor operated at shorter HRT (6 h) showed better H₂ productivity (17.3?±?1.1 L H₂/L-d) in comparison with the other one operated at 10-h HRT (12.4?±?1.6 L H₂/L-d).     

Chemical Modeling of Acid-Base Properties of Soluble Biopolymers Derived from Municipal Waste Treatment Materials

This work reports a study of the proton-binding capacity of biopolymers obtained from different materials supplied by a municipal biowaste treatment plant located in Northern Italy. One material was the anaerobic fermentation digestate of the urban wastes organic humid fraction. The others were the compost of home and public gardening residues and the compost of the mix of the above residues, digestate and sewage sludge. These materials were hydrolyzed under alkaline conditions to yield the biopolymers by saponification. The biopolymers were characterized by ¹³C NMR spectroscopy, elemental analysis and potentiometric titration. The titration data were elaborated to attain chemical models for interpretation of the proton-binding capacity of the biopolymers obtaining the acidic sites concentrations and their protonation constants. The results obtained with the models and by NMR spectroscopy were elaborated together in order to better characterize the nature of the macromolecules. The chemical nature of the biopolymers was found dependent upon the nature of the sourcing materials.     

Potential of the renewable energy development in Jammu and Kashmir,India

The future economic growth for India is likely to result in rapid and accelerated surge in energy demand, with expected shortages in terms of supply. Many of its current policies and strategies are aimed at the improvement and possible maximization of energy production from the renewable sector. It is also clear that while energy conservation and energy efficiency can make an important contribution, renewable energies will be essential to the solution and are likely to play an increasingly important role for providing enhanced energy access, reducing consumption of fossil fuels, and helping India pursue its low-carbon progressive pathway. However, most of the states in India, like the northernmost state of Jammu and Kashmir, have experienced an energy crisis over a sustained period of time and the government both at center and state level has to embark upon with these pressing issues in a more sustainable manner and accordingly initiate various renewable energy projects within these states. This paper will provide a broad-spectrum view about the energy situation within Jammu and Kashmir and will highlight the current policies along with future strategies for the optimal utilization of renewable energy resources.     

Biofuels in Spain: Market penetration analysis and competitiveness in the automotive fuel market

For several years the European Union (E.U.) has been promoting the use of biofuels due to their potential benefits such as the reduction of dependence on foreign energy imports (the raw materials can be produced within the E.U.), the more stable fossil fuel prices (they can replace fossil fuels on the market), the greenhouse gas (GHG) reduction (biofuels’ raw materials fix CO₂ from the atmosphere) and the fact that they can represent an additional source of income for the primary sector (biofuels’ raw materials are vegetables that can be grown and harvested).Despite the public aids (direct and indirect), biofuels are not competitive with fossil fuels at present, but it is possible that in the future the environment conditions change and biofuels might become competitive. It is difficult to assess whether this will happen or not, but it is possible to make an assessment of a future situation.This article presents two analyses with one objective: to determine if biofuels might become competitive in the future. The first analysis examines the dependencies of two quotations which have a strong relationship with fuels: the crude oil quotation and the CO₂ bond quotation. The analysis of these relationships may help to forecast the future competitiveness of biofuels. For instance, biofuels’ future competitiveness will be higher if their raw material costs are not related to crude oil quotations or if they are related in a negative way (the higher the crude oil quotations the lower the raw material biofuels’ cost). The second analysis focuses on the market penetration of biofuels in the Spanish market. There are data related to biofuels monthly consumption in Spain since 2007 and it is possible to know if biofuels are gaining market quota since then.     

On the distribution and performance implications of filteredinterferometric crosstalk in optical WDM networks

The distribution and performance implications of filtered interferometric crosstalk in optical networks is theoretically and experimentally studied. The probability density function is estimated by using a maximum entropy approach based on analytically derived statistical moments. The theoretical results are confirmed by relevant experimental data obtained from an amplitude shift keying direct detection (ASK/DD) system using directly, and externally modulated light sources. Power penalties are measured for both types of source modulation. The experimental results are in good agreement with theory     

Corrosion of API XL 52 steel in presence of Clostridium celerecrescens

During the characterization of sediments formed in pipelines transporting hydrocarbons, the knowledge of the microbiological diversity becomes very interesting, especially when it is related to microbiologically influenced corrosion (MIC). The presence of microorganisms is considered as one of the factors that affect the corrosion processes occurring at the pipeline; therefore, their corrosiveness must be determined. In this way, the identification of new species affecting the MIC processes is still considered relevant. In this work, the effect of Clostridium celerecrescens upon the corrosion of API KL 52 steel was evaluated. This microorganism was isolated and identified from the sediments collected during the inner cleaning procedures of a gas pipeline. The polarization resistance (PR) and electrochemical impedance spectroscopy (EIS) techniques were considered to estimate the microorganism behavior during the corrosion process. The results were complemented with a metal surface analysis, using a scanning electron microscope (SEM). The resistance values induced by the presence of the microorganisms clearly indicated that C. celerecrescens has an effect on the corrosion process occurring at the API XL 52 steel surface.     

Simultaneous degradation of atrazine and simazine by a binary culture of Stenotrophomonas maltophilia and Arthrobacter sp. in a two‐stage biofilm reactor

BACKGROUND: The impact of mixtures of chloro‐triazinic herbicides, such as atrazine and simazine, on aquatic ecosystems is of environmental concern. To study their biodegradation under various operational conditions, a binary community comprising Stenotrophomonas maltophilia and Arthrobacter sp. attached to the porous support of a packed bed reactor, was evaluated. RESULTS: The genetic analysis of the two atrazine‐degrading strains revealed that genes atzA, atzB, atzC are present in both bacteria, but only S. maltophilia possess atzD. Thus, by cultivating Arthrobacter sp. on these herbicides, cyanuric acid accumulation was observed. When the binary community was cultivated in the biofilm reactor, at all the loading rates probed, both herbicides were entirely removed. However, complete biodegradation of cyanuric acid was not achieved. CONCLUSIONS: Even with a two‐stage reactor, cyanuric acid was only partially removed. This fact could be attributed to the absence, in the second stage, of an easily degradable energy source, required by S. maltophilia for the uptake and cometabolic degradation of the recalcitrant heterocyclic ring. Responding to differences in nutritional conditions prevailing at each reactor stage, local differences in species' predominance were clearly detected by microbiological and molecular biology methods. Copyright © 2010 Society of Chemical Industry     

Hybrid RSOA and fibre Raman amplified long reach feeder link for WiMAX-on-fibre

A distributed fibre Raman amplified long reach optical access feeder link using a reflective semiconductor optical amplifier in the remote base station is experimentally demonstrated for supporting WiMAX-over-fibre transmission. The measured values for the error vector magnitude for quadrature phase shift keying and 16-ary quadrature amplitude modulation after 40 km of fibre transmission meet the IEEE 820.16 standard requirements.