Simultaneous removal of TOC and TSS in swine wastewater using the partial nitritation process

BACKGROUND: Considering biological nitrogen removal, the partial nitritation connected with the anaerobic ammonium oxidation (anammox) process is a promising alternative for nitrogen elimination at high loading rates. The objective of the present study was to evaluate the establishment and operation of a partial nitritation process in an airlift reactor with simultaneous removal of total organic carbon and suspended solids using swine wastewater. RESULTS: The partial nitritation reactor was inoculated with a nitrifying sludge at 2.1 gTSS L^?1 and fed with an UASB reactor effluent. High organic carbon loading rates, above 2 kgTOC m^?3 d^?1 have been shown to be potential inhibitors of the partial nitritation process due to competition between autotrophic and heterotrophic bacteria. In this study, the partial nitritation process was established using undiluted swine wastewater, with HRT of 24 h, 1.84 mgO₂ L^?1 (SD = 0.41) DO, loading rate of 1.14 gTOC L^?1 d^?1 and 0.91 gN‐NH₃ L^?1 d^?1 for more than 100 consecutive days. At the same time, the system proved to be an effective tool in TOC and TSS removal, reaching 84.9% (SD = 9.3) and 83.1% (SD = 0.1), respectively. CONCLUSION: This result enhances partial nitritation application as a technology for high load nitrogen converting, and allows the possibility of connection with anammox reactors. Copyright © 2012 Society of Chemical Industry     

Effects of ultrasonic pulsation of the welding current on the geometry of the fusion zone and heat-affected zone in submerged arc welding

This paper proposes investigation of an arc ultrasonic excitation technique in the SAW process in order to evaluate the main parameters’ influence associated with pulsed current on weld beads, such as the frequency and amplitude of ultrasonic excitation current. Therefore, an experimental bench was assembled, which consists of two power sources: a conventional welding source and another able to provide pulse current at ultrasonic frequencies. During the tests two ultrasonic excitation current amplitudes were employed, 25 A and 50 A, each one in three different pulse frequencies, 20, 50 and 80 kHz. Macrographs of these welds are observed, and width, penetration, molten area and heat-affected zone area (HAZ) are measured. As a result, contrary to information available in the literature, there were no significant changes in weld bead geometry, as well as in the HAZ, that could be attributed to the current excitation in studied frequencies.     

Falling film distillation column with heat transfer by means of a vapor chamber. Part II: operation with a temperature profile

Based on previous results and a new proposal for the configuration of falling film distillation columns heated by a vapor chamber operating at atmospheric pressure, the present study analyzed a different application for heat transfer by means of an the axial temperature profile in the same vapor chamber, generated by the presence of non-condensable gases. Experimental tests were performed with an ethanol–water mixture by varying the feed flow rate and vapor chamber temperature. This new heat transfer proposal allowed the formation of a temperature gradient inside the distillation tube (similarly to the isothermal proposal previously reported), thus indicating that this heat transfer method is feasible for a distillation unit. The results demonstrated that higher flow rates are suitable for the distillation of ethanol and water in this new proposal; the temperature profile operation shows the feasibility of this new heat transfer proposal in falling film distillation columns and encourages further studies on the optimization of the process and the evaluation of the energy consumption.     

Production,storage, fuel stations of hydrogen and its utilization in automotive applications-a review

Fossil fuels are responsible for a significant portion of the emissions of greenhouse gases. As the need to find renewable and environmentally friendly energy solutions grows, the tendency is for these sources increase in the vehicle matrices, gradually. Because of this, hydrogen appears as a potential alternative to fossil fuels. Hydrogen is one of the most abundant elements on the planet and can be obtained from numerous sources, such as water, biomass, natural gas, ethanol, among others. To be used in fuel cell vehicles or in internal combustion engines, hydrogen needs to go through stages such as production, storage and distribution. All of these steps need to be feasible in terms of technology, economics and also from the environmental point of view. Therefore, the objective of this study was to review the feasibility and impacts of all stages from production to final use of hydrogen as a resource for mobility purposes. This article provides a general discussion of the path which the hydrogen goes through from its source until its usage, approaching technological, economic and environmental issues that are essential for the viability of this economy. Moreover, it also presents the main challenges and research fields that need greater engagement by researchers and political decision-makers. The results indicate that hydrogen production techniques need more development in order to be competitive. Production methods that show the best average results are hybrid production methods, followed by thermal and photonic. The main difficulty in terms of storage is to obtain a good volumetric density. The volumetric density of the current compression storage is about 5,7 wt percent capacity (wt%). Fuel cells need to achieve better results in terms of system durability (current durability is approximately 120,000 km) and costs.     

Liposomal Delivery of Newly Identified Prophage Lysins in a Pseudomonas aeruginosa Model

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterium that presents resistance to several antibiotics, thus, representing a major threat to human and animal health. Phage-derived products, namely lysins, or peptidoglycan-hydrolyzing enzymes, can be an effective weapon against antibiotic-resistant bacteria. Whereas in Gram-positive bacteria, lysis from without is facilitated by the exposed peptidoglycan layer, this is not possible in the outer membrane-protected peptidoglycan of Gram-negative bacteria. Here, we suggest the encapsulation of lysins in liposomes as a delivery system against Gram-negative bacteria, using the model of P. aeruginosa. Bioinformatic analysis allowed for the identification of 38 distinct complete prophages within 66 P. aeruginosa genomes (16 of which newly sequenced) and led to the identification of 19 lysins of diverse sequence and function, 5 of which proceeded to wet lab analysis. The four purifiable lysins showed hydrolytic activity against Gram-positive bacterial lawns and, on zymogram assays, constituted of autoclaved P. aeruginosa cells. Additionally, lysins Pa7 and Pa119 combined with an outer membrane permeabilizer showed activity against P. aeruginosa cells. These two lysins were successfully encapsulated in DPPC:DOPE:CHEMS (molar ratio 4:4:2) liposomes with an average encapsulation efficiency of 33.33% and 32.30%, respectively. The application of the encapsulated lysins to the model P. aeruginosa led to a reduction in cell viability and resulted in cell lysis as observed in MTT cell viability assays and electron microscopy. In sum, we report here that prophages may be important sources of new enzybiotics, with prophage lysins showing high diversity and activity. In addition, these enzybiotics following their incorporation in liposomes were able to potentiate their antibacterial effect against the Gram-negative bacteria P. aeruginosa, used as the model.     

A Weighted Delaunay Triangulation Framework for Merging Triangulations in a Connectivity Oblivious Fashion

Simplicial meshes are useful as discrete approximations of continuous spaces in numerical simulations. In some applications, however, meshes need to be modified over time. Mesh update operations are often expensive and brittle, making the simulations unstable. In this paper we propose a framework for updating simplicial meshes that undergo geometric and topological changes. Instead of explicitly maintaining connectivity information, we keep a collection of weights associated with mesh vertices, using a Weighted Delaunay Triangulation (WDT). These weights implicitly define mesh connectivity and allow direct merging of triangulations. We propose two formulations for computing the weights, and two techniques for merging triangulations, and finally illustrate our results with examples in two and three dimensions.