Biodegradation and biotransformation of wastewater organics as precursors of disinfection byproducts in water

Laboratory experiments were carried out to investigate wastewater organics as the precursors of disinfection byproducts (DBPs) in drinking water supply. The focus was on the change in wastewater DBP precursors during biological degradation under simulated natural conditions. The wastewater and its treated secondary effluent were characterized for DBP formation potential (DBPFP) and DBP speciation profile, including trihalomethanes, haloacetic acids, chloral hydrate, and nitrogen-containing DBPs. Several model organic compounds, including humic acid, tannic acid, glucose, starch, glycine, and bovine serum albumin (BSA), were used to represent the different types of organic pollutants in wastewater discharge. The results show that the DBPFP of wastewater decreased after biodegradation, but the remaining organic matter had a greater DBPFP yield with chlorine. Different model organics displayed different changes in DBPFP during biodegradation. The DBPFP remained largely unchanged for the glycine solution, decreased greatly for the tannic acid and BSA solutions, and increased nearly 3-fold for the glucose and starch solutions after 10d of biodegradation. Meanwhile, the DBPFP yield increased from 3 for glycine to 51μg DBP mg-1 C for its degradation residue, and from 1 for glucose and starch to 87 and 38μg DBP mg-1 C for their organic residues, respectively. Although biodegradation may effectively remove some DBP precursors, biotransformation during the process produces new DBP precursors in the form of soluble microbial products (SMPs). The experimental results reveal that SMPs may be an important source of wastewater-derived DBP precursors in natural waters. © 2010 Elsevier Ltd.postprin

Removal of soluble microbial products as the precursors of disinfection by-products in drinking water supplies

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Ballistic Transport in Monolayer Black Phosphorus Transistors

© 2014 IEEE.We report a comprehensive theoretical investigation of ballistic quantum transport in monolayer black phosphorus (ML-BP) field-effect transistors (FETs). Our calculation is from tight binding atomistic model based on the nonequilibrium Green's function formalism. Several important device properties, including the drain current, ON-OFF ratio, transfer characteristic, short channel effects, intrinsic delay, and power delay product are determined against the channel length, transport direction, bias, and gate voltages. The atomistic simulation provides microscopic understanding of the device physics. Due to the anisotropic band structure of ML-BP, an orientation-dependent transport characteristic manifests itself in the major transistor properties. Comparing device performance in the zigzag and armchair direction (AD), we predict that transport along the AD has higher ON-state current and faster switching speed due to the lighter carrier effective mass. Comparing with ML MoS2 FET, ML-BP FET produces higher current density and faster switching speed, but costs more switching energy. Double gated ML-BP FETs show promising device characteristics that fulfill the international technology roadmap for semiconductors requirements in the 10-year horizon.published_or_final_versio

Quadtree based mouse trajectory analysis for efficacy evaluation of voice-enabled CAD

Voice-enabled applications have caught considerable research interest in recent years. It is generally believed that voice based interactions can improve the working efficiencies and the overall productivities. Quantitative evaluations on the performance boost by using such Human-Computer interactions (HCI) are therefore necessary to justify the claimed efficacies and the usefulness of the HCI system. In this paper, a quadtree based approach is proposed to analyze the mouse movement distributions in the proposed Voice-enabled Computer-Aided Design (VeCAD) system. The mouse tracker keeps a record of all the mouse movement during the solid modeling process, and a quadtree based approach is applied to analyze the mouse trajectory distributions in both the traditional CAD and the VeCAD system. Our experiments show that the mouse movement is significantly reduced when voice is used to activate CAD modeling commands. ©2009 IEEE.published_or_final_versionThe IEEE International Conference on Virtual Environments, Human-Computer Interfaces, and Measurements Systems (VECIMS) 2009, Hong Kong, 11-13 May 2009. In Conference Proceedings, 2009, p. 196-20

Growth of long-period gratings in H₂-loaded fiber after 193-nm UV inscription

2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Movements of genes between populations: are pollinators more effective at transferring their own or plant genetic markers?

The transfer of genes between populations is increasingly important in a world where pollinators are declining, plant and animal populations are increasingly fragmented and climate change is forcing shifts in distribution. The distances that pollen can be transported by small insects are impressive, as is the extensive gene flow between their own populations. We compared the relative ease by which small insects introduce genetic markers into their own and host-plant populations. Gene flow via seeds and pollen between populations of an Asian fig species were evaluated using cpDNA and nuclear DNA markers, and between-population gene flow of its pollinator fig wasp was determined using microsatellites. This insect is the tree's only pollinator locally, and only reproduces in its figs. The plant's pollen-to-seed dispersal ratio was 9.183-9.437, smaller than that recorded for other Ficus. The relative effectiveness of the pollinator at introducing markers into its own populations was higher than the rate it introduced markers into the plant's populations (ratio = 14 : 1), but given the demographic differences between plant and pollinator, pollen transfer effectiveness is remarkably high. Resource availability affects the dispersal of fig wasps, and host-plant flowering phenology here and in other plant-pollinator systems may strongly influence relative gene flow rates

Characterization of soluble microbial products as precursors of disinfection byproducts in drinking water supply

Water pollution by wastewater discharge can cause the problem of disinfection byproducts (DBPs) in drinking water supply. In this study, DBP formation characteristics of soluble microbial products (SMPs) as the main products of wastewater organic biodegradation were investigated. The results show that SMPs can act as DBP precursors in simulated wastewater biodegradation process. Under the experimental conditions, stabilized SMPs had DBPFP (DBP formation potential) yield of around 5.6 mumol mmol(-1)-DOC (dissolved organic carbon) and DBP speciation profile different from that of the conventional precursor, natural organic matter (NOM). SMPs contained polysaccharides, proteins, and humic-like substances, and the latter two groups can act as reactive DBP precursors. SMP fraction with molecular weight of <1 kDa accounted for 85% of the organic carbon and 65% of the DBP formation. As small SMP molecules are more difficult to remove by conventional water treatment processes, more efforts are needed to control wastewater-derived DBP problem in water resource management.postprin

Negative capacitance transistors with monolayer black phosphorus

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