Computational and experimental investigation of biofilm disruption dynamics induced by high-velocity gas jet impingement

Peer ReviewedPostprint (published version

An ISFET-based anion sensor for the potentiometric detection of organic acids in liquid chromatography

An ion-selective field effect transistor (ISFET) was applied as a potentiometric detector in liquid chromatography (LC) for the determination of organic acids. The ISFET was prepared by coating the gate insulator of the encapsulated transistor with a poly(vinyl chloride) (PVC) matrix membrane containing methyltridodecylammoniumchloride, which enables the detection of organic anions. The ISFET was tested for its applicability as detector for carboxylic acids in ion-exchange and reversed-phase chromatography. Its analytical characteristics were compared to those of a coated-wire electrode (CWE) and of a conventional type of ion-selective electrode (ISE)

Assessing microbial competition in a hydrogen‐based membrane biofilm reactor (MBfR) using multidimensional modeling

The membrane biofilm reactor (MBfR) is a novel technology that safely delivers hydrogen to the base of a denitrifying biofilm via gas‐supplying membranes. While hydrogen is an effective electron donor for denitrifying bacteria (DNB), it also supports sulfate‐reducing bacteria (SRB) and methanogens (MET), which consume hydrogen and create undesirable by‐products. SRB and MET are only competitive for hydrogen when local nitrate concentrations are low, therefore SRB and MET primarily grow near the base of the biofilm. In an MBfR, hydrogen concentrations are greatest at the base of the biofilm, making SRB and MET more likely to proliferate in an MBfR system than a conventional biofilm reactor. Modeling results showed that because of this, control of the hydrogen concentration via the intramembrane pressure was a key tool for limiting SRB and MET development. Another means is biofilm management, which supported both sloughing and erosive detachment. For the conditions simulated, maintaining thinner biofilms promoted higher denitrification fluxes and limited the presence of SRB and MET. The 2‐d modeling showed that periodic biofilm sloughing helped control slow‐growing SRB and MET. Moreover, the rough (non‐flat) membrane assembly in the 2‐d model provided a special niche for SRB and MET that was not represented in the 1‐d model. This study compared 1‐d and 2‐d biofilm model applicability for simulating competition in counter‐diffusional biofilms. Although more computationally expensive, the 2‐d model captured important mechanisms unseen in the 1‐d model. Biotechnol. Bioeng. 2015;112: 1843–1853. © 2015 Wiley Periodicals, Inc.Competition between denitrifying (DNB) and undesirable sulfate‐reducing bacteria (SRB) and methanogens (MET) were evaluated in a hydrogen‐based, membrane biofilm reactor (MBfR) through 1‐d and 2‐d biofilm modeling studies. The 2‐d model allowed novel mechanisms, not previously described for MBfRs, to be captured.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112211/1/bit25607.pd

Modeling the radiative, thermal and chemical microenvironment of 3D scanned corals

Reef building corals are efficient biological collectors of solar radiation and consist of a thin stratified tissue layer spread over a light scattering calcium carbonate skeleton surface that together construct complex three dimensional (3D) colony structures forming the foundation of coral reefs. They exhibit a vast diversity of structural forms to maximize photosynthesis of their dinoflagellate endosymbionts (Symbiodiniaceae), while simultaneously minimizing photodamage, offer resistance to hydrodynamic stress, reduce attack by predators and increase prey capture and heterotrophic feeding. The symbiosis takes place in the presence of dynamic gradients of light, temperature and chemical species that are affected by the interaction of incident irradiance and water flow with the coral colony. We developed a multiphysics modelling approach to simulate the microscale spatial distribution of light, temperature and O2 in a coral fragment with its morphology determined by 3D scanning techniques. Model results compared well with spatial measurements of light, O2 and temperature under similar flow and light conditions. The model enabled us to infer the effect of coral morphology and light scattering in tissue and skeleton on the internal light environment experienced by the endosymbionts, as well as the combined contribution of light, water flow and ciliary movement on O2 and temperature distributions in the coral

Periodic venting of MABR lumen allows high removal rates and high gas-transfer efficiencies

The membrane-aerated biofilm reactor (MABR) is a novel treatment technology that employs gas-supplying membranes to deliver oxygen directly to a biofilm growing on the membrane surface. When operated with closed-end membranes, the MABR provides 100-percent oxygen transfer efficiencies (OTE), resulting in significant energy savings. However, closed-end MABRs are more sensitive to back-diffusion of inert gases, such as nitrogen. Back-diffusion reduces the average oxygen transfer rates (OTR), consequently decreasing the average contaminant removal fluxes (J). We hypothesized that venting the membrane lumen periodically would increase the OTR and J. Using an experimental flow cell and mathematical modeling, we showed that back-diffusion gas profiles developed over relatively long timescales. Thus, very short ventings could re-establish uniform gas profiles for relatively long time periods. Using modeling, we systematically explored the effect of the venting interval (time between ventings). At moderate venting intervals, opening the membrane for 20 s every 30 min, the venting significantly increased the average OTR and J without substantially impacting the OTEs. When the interval was short enough, in this case shorter than 20 min, the OTR was actually higher than for continuous open-end operation. Our results show that periodic venting is a promising strategy to combine the advantages of open-end and closed end operation, maximizing both the OTR and OTE.Primary funding for this work was from Water Environment Research Foundation (WERF) project U2R14. Additional funding was provided by the Basque Government, partially financing Patricia Pérez, and the Spanish Ministry of Economics and Competitiveness and the European Regional Development Fund (FEDER), project “Innovative Integrated Biological Processes for Nutrients Removal (PBi2)” (CTM2012-36227)

Del MA al mar. El museo de la historia de Andalucía

Un edificio fuerte y radical evocará en su seno la semblanza de una comunidad con un rico pasado cultural que se proyecta hacia el futuro. El arquitecto explica las claves de este centro, levantado en Granada

Multiphysics modelling of photon, mass and heat transfer in coral microenvironments

Coral reefs are constructed by calcifying coral animals that engage in a symbiosis with dinoflagellate microalgae harboured in their tissue. The symbiosis takes place in the presence of steep and dynamic gradients of light, temperature and chemical species that are affected by the structural and optical properties of the coral and their interaction with incident irradiance and water flow. Microenvironmental analyses have enabled quantification of such gradients and bulk coral tissue and skeleton optical properties, but the multi-layered nature of corals and its implications for the optical, thermal and chemical microenvironment remains to be studied in more detail. Here, we present a multiphysics modelling approach, where three-dimensional Monte Carlo simulations of the light field in a simple coral slab morphology with multiple tissue layers were used as input for modelling the heat dissipation and photosynthetic oxygen production driven by photon absorption. By coupling photon, heat and mass transfer, the model predicts light, temperature and O 2 gradients in the coral tissue and skeleton, under environmental conditions simulating, for example, tissue contraction/expansion, symbiont loss via coral bleaching or different distributions of coral host pigments. The model reveals basic structure–function mechanisms that shape the microenvironment and ecophysiology of the coral symbiosis in response to environmental change. </jats:p

REMOVED: A Multi–dimensional Model for Scaling in Reverse Osmosis Devices

This article has been removed: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been removed at the request of the Executive Publisher.This article has been removed because it was published without the permission of the author(s)