Effects of integrated fixed film activated sludge media on activated sludge settling in biological nutrient removal systems

Integrated fixed film activated sludge (IFAS) is an increasingly popular modification of conventional activated sludge, consisting of the addition of solid media to bioreactors to create hybrid attached/suspended growth systems. While the benefits of this technology for improvement of nitrification and other functions are well-demonstrated, little is known about its effects on biomass settleability. These effects were evaluated in parallel, independent wastewater treatment trains, with and without IFAS media, both at the pilot (at two solids residence times) and full scales. While all samples demonstrated good settleability, the Control (non-IFAS) systems consistently demonstrated small but significant (p < 0.05) improvements in settleability relative to the IFAS trains. Differences in biomass densities were identified as likely contributing factors, with Control suspended phase density > IFAS suspended phase density > IFAS attached phase (biofilm) density. Polyphosphate content (as non-soluble phosphorus) was well-correlated with density. This suggested that the attached phases had relatively low densities because of their lack of anaerobic/aerobic cycling and consequent low content of polyphosphate-accumulating organisms, and that differences in enhanced biological phosphorus removal performance between the IFAS and non-IFAS systems were likely related to the observed differences in density and settleability for the suspended phases. Decreases in solids retention times from 8 to 4 days resulted in improved settleability and increased density in all suspended phases, which was related to increased phosphorus content in the biomass, while no significant changes in density and phosphorus content were observed in attached phases.     

Invertebrate mercury bioaccumulation in permanent, seasonal, and flooded rice wetlands within California's Central Valley

We examined methylmercury (MeHg) bioavailability in four of the most predominant wetland habitats in California's Central Valley agricultural region during the spring and summer: white rice, wild rice, permanent wetlands, and shallowly-flooded fallow fields. We sampled MeHg and total mercury (THg) concentrations in two aquatic macroinvertebrate taxa at the inlets, centers, and outlets of four replicated wetland habitats (8 wetlands total) during two time periods bounding the rice growing season and corresponding to flood-up and pre-harvest (96 total samples). In general, THg concentrations (mean ± standard error) in Notonectidae (Notonecta, back swimmers; 1.18 ± 0.08 µg g^− 1 dry weight [dw]) were higher than in Corixidae (Corisella, water boatmen; 0.89 ± 0.06 µg g^− 1 dw, MeHg: 0.74 ± 0.05 µg g^− 1 dw). MeHg concentrations were correlated with THg concentrations in Corixidae (R² = 0.80) and 88% of THg was in the MeHg form. Wetland habitat type had an important influence on THg concentrations in aquatic invertebrates, but this effect depended on the sampling time period and taxa. In particular, THg concentrations in Notonectidae, but not Corixidae, were higher in permanent wetlands than in white rice, wild rice, or shallowly-flooded fallow fields. THg concentrations in Notonectidae were higher at the end of the rice growing season than near the time of flood-up, whereas THg concentrations in Corixidae did not differ between time periods. The effect of wetland habitat type was more prevalent near the end of the rice growing season, when Notonectidae THg concentrations were highest in permanent wetlands. Additionally, invertebrate THg concentrations were higher at water outlets than at inlets of wetlands. Our results indicate that although invertebrate THg concentrations increased from the time of flood-up to draw-down of wetlands, temporarily flooded habitats such as white rice, wild rice, and shallowly-flooded fallow fields did not have higher THg or MeHg concentrations in invertebrates than permanent wetlands.     

Electrospun ultrathin nylon fibers for protective applications

Electrospun nylon 6 fiber mats were deposited on woven 50/50 nylon/cotton fabric with the motive of making them into protective material against submicron‐level aerosol chemical and biological threats. Polymer solution concentration, electrospinning voltage, and deposition areal densities were varied to establish the relationships of processing‐structure‐filtration efficiency of electrospun fiber mats. A high barrier efficiency of greater than 99.5% was achieved on electrospun fiber mats without sacrificing air permeability and pressure drop. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Life-cycle carbon and cost analysis of energy efficiency measures in new commercial buildings

Energy efficiency in new building construction has become a key target to lower nation-wide energy use. The goals of this paper are to estimate life-cycle energy savings, carbon emission reduction, and cost-effectiveness of energy efficiency measures in new commercial buildings using an integrated design approach, and estimate the implications from a cost on energy-based carbon emissions. A total of 576 energy simulations are run for 12 prototypical buildings in 16 cities, with 3 building designs for each building-location combination. Simulated energy consumption and building cost databases are used to determine the life-cycle cost-effectiveness and carbon emissions of each design. The results show conventional energy efficiency technologies can be used to decrease energy use in new commercial buildings by 20-30% on average and up to over 40% for some building types and locations. These reductions can often be done at negative life-cycle costs because the improved efficiencies allow the installation of smaller, cheaper HVAC equipment. These improvements not only save money and energy, but reduce a building’s carbon footprint by 16% on average. A cost on carbon emissions from energy use increases the return on energy efficiency investments because energy is more expensive, making some cost-ineffective projects economically feasible.     

Coupled mechanical and chemical processes in engineered geothermal reservoirs with dynamic permeability

A model is developed to represent mechanical strain, stress-enhanced dissolution, and shear dilation as innately hysteretic and interlinked processes in rough contacting fractures. The model is incorporated into a numerical simulator designed to examine permeability change and thermal exchange in chemically active and deformable fractured reservoirs. A candidate engineered geothermal reservoir system (EGS) is targeted. The mechanistic model is able to distinguish differences between the evolution of fluid transmission characteristics of (1) small scale, closely spaced fractures, and (2) large-scale, more widely spaced fractures. Alternate realizations of fracture frequency and scale, exhibiting identical initial bulk permeability, lead to significantly different conclusions regarding permeability evolution and thermal drawdown within the reservoir. Reactivation, primarily through mechanical shear, of pervasive, large-scale fractures is shown capable of causing both hydraulic and thermal short circuiting. Small variations in fracture scale impact the balance between the efficiency of thermal transfer and the rate of fluid circulation. Stress-enhanced chemical dissolution, initially at equilibrium within the reservoir, may be reactivated as fractures are forced out of equilibrium during hydraulic fracturing. At the conditions examined (250 °C reservoir with 70 °C injection), however, shear dilation exerts dominant control over changes to permeability. Heterogeneity in permeability, generated from a normal distribution of fracture spacing, impacts thermal breakthrough times at the withdrawal well, as well as withdrawal rates. For the given conditions, spatial variability over ～1 order of magnitude leads to a reduction of ～10% in withdrawal rates compared to a spatially uniform system. Permeability is a strongly dynamic property and at geothermal conditions is influenced by the full suite of THMC interactions.     

Revisiting the Worksite in Worksite Health Campaigns: Evidence From a Multisite Organ Donation Campaign

This article advances the beginnings of a general theory of organizational features to aid in understanding why health campaigns that work well in one organization may be ineffectual in another organization. The physical, social, and information structures of organizations are theorized to create an interaction environment that is distinct to each organization and that influences health campaigns. To test this argument, an organ donation campaign was conducted in 46 organizations. Multilevel modeling yielded mixed findings. Physical structure was negatively associated with signing an organ donor card. Social structure and information structure were positively associated with communication with coworkers about donation and communicative peer influence. Industry type was positively associated with knowledge change.     

Simple model to predict gel formation in olefin‐diene copolymerizations catalyzed by constrained‐geometry complexes

We have developed an analytical model to predict the onset of gel formation in ethylene/1‐octene/1,9‐decadiene terpolymerizations using constrained‐geometry catalysts. The model relies on three kinetic parameters to characterize the catalyst response. Polymer resins have been synthesized in a continuous stirred‐tank reactor to determine the model parameters, and to validate the model predictions for polymer properties and for the onset of gel formation and reactor fouling. The experimental results indicate that the free double bonds in 1,9‐decadiene are as reactive as those found in 1‐octene, and that the reactivity of 1,9‐decadiene double bonds decreases after the 1,9‐decadiene molecules become part of a polymer chain. The model predictions of polymer properties agree well with chromatographic, density, and mass‐balance data. Moreover, the model was successful in preventing unintended reactor fouling during the duration of the experimental campaign. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Parameter identification and model based predictive control of temperature inside a house

HVAC (Heating, Ventilation and Air Conditioning) systems used for heating or cooling buildings, consume a considerable amount of energy. To optimize the energy consumption, the behavior of occupants must be changed. This can be achieved by providing information and suggestions to occupants. A first step is developing of a less expensive and non-invasive measurement system and metering of the electricity and heat consumed. Based on collected experimental data, it can identify the parameters of a thermal model of the house. The model obtained will be used to simulate different aspects that can help to reduce the energy consumption. This paper presents a simple solution for thermal modeling of a house which includes experimental identification of the model's parameters. Such data are used to simulate the thermal behavior of the house and to obtain solutions to reduce energy consumption. In simulation, the control of the thermal system is performed using a model based predictive control algorithm.