Fate of dissolved organic nitrogen in two stage trickling filter process

Dissolved organic nitrogen (DON) represents a significant portion of nitrogen in the final effluent of wastewater treatment plants (WWTPs). Biodegradable portion of DON (BDON) can support algal growth and/or consume dissolved oxygen in the receiving waters. The fate of DON and BDON has not been studied for trickling filter WWTPs. DON and BDON data were collected along the treatment train of a WWTP with a two-stage trickling filter process. DON concentrations in the influent and effluent were 27% and 14% of total dissolved nitrogen (TDN). The plant removed about 62% and 72% of the influent DON and BDON mainly by the trickling filters. The final effluent BDON values averaged 1.8 mg/L. BDON was found to be between 51% and 69% of the DON in raw wastewater and after various treatment units. The fate of DON and BDON through the two-stage trickling filter treatment plant was modeled. The BioWin v3.1 model was successfully applied to simulate ammonia, nitrite, nitrate, TDN, DON and BDON concentrations along the treatment train. The maximum growth rates for ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria, and AOB half saturation constant influenced ammonia and nitrate output results. Hydrolysis and ammonification rates influenced all of the nitrogen species in the model output, including BDON.     

Quantum dot-based screening system for discovery of g protein-coupled receptor agonists

Cellular imaging has emerged as an important tool to unravel biological complexity and to accelerate the drug-discovery process, including cell-based screening, target identification, and mechanism of action studies. Recently, semiconductor nanoparticles known as quantum dots (QDs) have attracted great interest in cellular imaging applications due to their unique photophysical properties such as size, tunable optical property, multiplexing capability, and photostability. Herein, we show that QDs can also be applied to assay development and eventually to high-throughput/content screening (HTS/HCS) for drug discovery. We have synthesized QDs modified with PEG and primary antibodies to be used as fluorescent probes for a cell-based HTS system. The G protein-coupled receptor (GPCR) family is known to be involved in most major diseases. We therefore constructed human osteosarcoma (U2OS) cells that specifically overexpress two types of differently tagged GPCRs: influenza hemagglutinin (HA) peptide-tagged κ-opioid receptors (κ-ORs) and GFP-tagged A3 adenosine receptors (A3AR). In this study, we have demonstrated that 1) anti-HA antibody-conjugated QDs could specifically label HA-tagged κ-ORs, 2) subsequent treatment of QD-tagged GPCR agonists allowed agonist-induced translocation to be monitored in real time, 3) excellent emission spectral properties of QD permitted the simultaneous detection of two GPCRs in one cell, and 4) the robust imaging capabilities of the QD-antibody conjugates could lead to reproducible quantitative data from high-content cellular images. These results suggest that the present QD-based GPCR inhibitor screening system can be a promising platform for further drug screening applications.     

Electrochemical assembly of MnO(2) on ionic liquid-graphene films into a hierarchical structure for high rate capability and long cycle stability of pseudocapacitors

Hierarchical nanostructures are of prime importance due to their large surface area, easy accessibility to reaction sites, fast ion and electron transport, and mechanical integrity. Herein, we demonstrate the synthesis of hierarchically structured MnO(2)/ionic liquid-reduced graphene oxide (IL-RGO) nanocomposites through the electrochemical self-assembly. The structures of MnO(2)/IL-RGO nanocomposites and their formation mechanism are investigated by spectroscopic methods and as a consequence, correlated with the electrochemical behaviours. The specific capacitance (511 F g(-1)) of conformally MnO(2)-deposited IL-RGO composites is significantly higher than 159 F g(-1) of pure MnO(2) film. High rate capability (61% retention at 30 A g(-1)) of the MnO(2)/IL-RGO composite is attributed to the facilitated ion diffusion and electron transport, whereas its long cycle life (95% retention after 2000 cycles) is related to the mechanical robustness. These results provide a new insight into the rational design of hierarchical and complex heterostructures consisting of carbon nanomaterials and metal oxides for applications in energy conversion and storage.     

Highly ordered large-area colloid templates for nanostructured TiO2 thin film gas sensors

We report a novel process that uses highly ordered colloidal templating to fabricate nanostructured TiO2 thin film gas sensors. An O2 plasma treatment is used to decrease the contact angle of a water droplet on a SiO2/Si substrate from 46 degrees to 3 degrees. The formation of this hydrophilic surface enhances the adhesion of polystyrene microspheres to the substrate during the spin coating of the colloidal solution, leading to a large-area colloid template of closely packed monolayer microspheres on the substrates. Embossed TiO2 thin film gas sensors fabricated through highly ordered colloidal templating using O2 plasma exhibit substantially enhanced gas sensing performance as compared to those without surface treatments prior to colloidal templating.     

Importance and measurement of decay rate when assessing nitrification kinetics.

Nitrification kinetics are important for process design, optimization and capacity rating of activated sludge wastewater treatment plants. Assessment of nitrification behaviour historically has focused on measuring the nitrifier maximum specific growth rate, micro(AUT). Very little attention has been directed at the of nitrifier organism rate has been assumed negligible. However, incorrect assessment of decay rate leads to errors in the micro(AUT) estimate; the magnitude of the error depends on the micro(AUT) measurement method employed. This paper illustrates why decay rate is important when measuring micro(AUT), and that the decay rate is significant. The paper also explains why measurement methods for nitrifier decay may have underestimated the decay rate. Results from an experiment incorporating improvements to previously suggested methods and data analysis are presented.     

Human–machine function allocation: a functional modelling approach

Function allocation between humans and systems is an important factor regarding safety, reliability and efficiency of industrial processes. One should allocate functions in order to maximise the operator's situation understanding and ability to handle unexpected events. Functional models can be used to study function allocation in a process control environment, because they explicitly describe functions and tasks of both the plant and the operator. The Halden Reactor Project is currently engaged in such a project called function allocation methods (FAME), aimed specifically at the work in a nuclear power plant control room. This paper describes the main features of the approach, and discusses how functional modelling can be used to address the issue of how much information is necessary for the operator, and thereby give a basis for how functions should be allocated.     

Health survey of former workers in a Norwegian coke plant: Part. 1. Estimation of historical exposures

OBJECTIVE: To estimate historical exposure levels at a coke plant for all agents considered to be of importance for epidemiological studies of mortality and cancer incidence. METHODS: Time weighted average exposure (8 h TWA) was estimated based on personal measurements for polycyclic aromatic hydrocarbons (PAHs) and carbonaceous particulates. Exposure to quartz was estimated relative to the concentration of carbonaceous particulates. These estimates were adjusted for the use of airstream helmets. Exposure to other agents were estimated qualitatively (asbestos, benzene, and arsenic) or semi-quantitatively (carbon monoxide (CO) and heat) based on measurements and other indicators of exposure. RESULTS: Exposure to PAHs was highest for those who worked at the top of the ovens (300 micrograms/m3) in the period from 1970-6. The estimated PAH exposure was reduced to an average of 65 micrograms/m3 after the introduction of exposure control measures in 1976. The estimates for carbonaceous particulates ranged from 1 to 16 mg/m3, with the highest exposure for workers at the top of the ovens and at the coke screening station. CONCLUSIONS: The exposure of greatest concern in this study is to PAHs, but exposures to carbonaceous particulates and CO may also be of importance. The major limitations of this study are the lack of personal measurements before 1975 and the total lack of measurements for some of the exposed categories of workers. Despite these limitations, we think that this assessment reflects the actual exposures for most of the former employees. The assessment thus provides a reasonable tool for the subsequent epidemiological study and for future epidemiological follow up studies at the coke plant.     

Polypropylene in the melt state as a medium for in situ synthesis of copper nanoparticles

Copper nanoparticles were in situ synthesized into a polypropylene matrix in the melt state. Three different routes were studied depending on the method used for the addition of a copper salt: (1) directly as powder; (2) dissolved in water; and (3) dissolved in water with a reducing agent. The first route produced microcrystal, whereas the second route allowed the synthesis of nanoparticles (～20 nm) homogeneously dispersed in the polymer matrix. By changing the concentration of the reducing agent in the copper solution (third route), a control of the copper structure in the polymer was possible and salt‐based or metal/oxide nanoparticles could be obtained. All these composites were able to release copper ions depending on the characteristic of the nanoparticles present in the polymer. Noteworthy, the resulting polymer/copper composites displayed strong antimicrobial behavior against Escherichia coli. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3406–3411, 2014