Influences of Combined Organic Fouling and Inorganic Scaling on Flux and Fouling Behaviors in Forward Osmosis

This study investigated the influence of combined organic fouling and inorganic scaling on the flux and fouling behaviors of thin-film composite (TFC) forward osmosis (FO) membranes. Two organic macromolecules, namely, bovine serum albumin (BSA) and sodium alginate (SA), and gypsum (GS), as an inorganic scaling agent, were selected as model foulants. It was found that GS scaling alone caused the most severe flux decline. When a mixture of organic and inorganic foulants was employed, the flux decline was retarded, compared with when the filtration was performed with only the inorganic scaling agent (GS). The early onset of the conditioning layer formation, which was due to the organics, was probably the underlying mechanism for this inhibitory phenomenon, which had suppressed the deposition and growth of the GS crystals. Although the combined fouling resulted in less flux decline, compared with GS scaling alone, the concoction of SA and GS resulted in more fouling and flux decline, compared with the mixture of BSA and GS. This was because of the carboxyl acidity of the alginate, which attracted calcium ions and formed an intermolecular bridge

Membrane and Electrochemical Processes for Water Desalination: A Short Perspective and the Role of Nanotechnology

In the past few decades, membrane-based processes have become mainstream in water desalination because of their relatively high water flux, salt rejection, and reasonable operating cost over thermal-based desalination processes. The energy consumption of the membrane process has been continuously lowered (from >10 kWh m(-3) to similar to 3 kWh m(-3)) over the past decades but remains higher than the theoretical minimum value (similar to 0.8 kWh m(-3)) for seawater desalination. Thus, the high energy consumption of membrane processes has led to the development of alternative processes, such as the electrochemical, that use relatively less energy. Decades of research have revealed that the low energy consumption of the electrochemical process is closely coupled with a relatively low extent of desalination. Recent studies indicate that electrochemical process must overcome efficiency rather than energy consumption hurdles. This short perspective aims to provide platforms to compare the energy efficiency of the representative membrane and electrochemical processes based on the working principle of each process. Future water desalination methods and the potential role of nanotechnology as an efficient tool to overcome current limitations are also discussed

CRISPR elements provide a new framework for the genealogy of the citrus canker pathogen Xanthomonas citri pv. citri

Background: Xanthomonads are an important clade of Gram-negative bacteria infecting a plethora of economically important host plants, including citrus. Knowledge about the pathogen's diversity and population structure are prerequisite for epidemiological surveillance and efficient disease management. Rapidly evolving genetic loci, such as Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), are of special interest to develop new molecular typing tools. Results: We analyzed CRISPR loci of 56 Xanthomonas citri pv. citri strains of world-wide origin, a regulated pathogen causing Asiatic citrus canker in several regions of the world. With one exception, 23 unique sequences built up the repertoire of spacers, suggesting that this set of strains originated from a common ancestor that already harbored these 23 spacers. One isolate originating from Pakistan contained a string of 14 additional, probably more recently acquired spacers indicating that this genetic lineage has or had until recently the capacity to acquire new spacers. Comparison of CRISPR arrays with previously obtained molecular typing data, such as amplified fragment length polymorphisms (AFLP), variable-number of tandem-repeats (VNTR) and genome-wide single-nucleotide polymorphisms (SNP), demonstrated that these methods reveal similar evolutionary trajectories. Notably, genome analyses allowed to generate a model for CRISPR array evolution in X. citri pv. citri, which provides a new framework for the genealogy of the citrus canker pathogen. Conclusions: CRISPR-based typing will further improve the accuracy of the genetic identification of X. citri pv. citri outbreak strains in molecular epidemiology analyses, especially when used concomitantly with another genotyping method

Pre-Concentration of Iron-Rich Sphalerite by Magnetic Separation

With the rise in metal prices and the growing importance of metallic minerals in the South Korean economy, there has been a steadily increasing demand to redevelop metal mines that have been shut down since the 1990s. However, it is not possible to ensure that such plans are economically feasible by using conventional mining processes, mainly flotation, because of low ore grade and complex mineral compositions. To improve the efficiency, and to reduce the operating cost of the entire process, pre-concentration by magnetic separation of Pb–Zn deposits has been investigated to reduce the mass and improve the grade of feed samples that are loaded into the flotation system. The results show that the response of sphalerite to magnetic separation varied as a function of its iron content: iron-rich sphalerite was recovered at magnetic intensities below 0.65 T, and relatively pure sphalerite was recovered at magnetic intensities above 0.85 T. Therefore, Pb–Zn ore could be sufficiently pre-concentrated by magnetic separation between 0.65 and 0.85 T to remove low-grade target elements. As a result, the mass of the sample fed into the flotation system was reduced almost by half, and the grade of zinc, lead, and copper was enhanced by 65%, 55%, and 33%, respectively. Therefore, it is possible to improve the efficiency of the entire process by reducing the amount of the sample to be fed to subsequent processes, such as grinding and flotation, while minimizing loss of the target mineral through magnetic separation

Numerical model-based analysis of energy-efficient reverse osmosis (EERO) process : performance simulation and optimization

We conducted a feasibility study of the energy-efficient reverse osmosis (EERO) process, which is a multi-stage membrane system that integrates single-stage reverse osmosis (SSRO) and a countercurrent membrane cascade with recycle (CMCR). To this end, we developed a numerical model for the 1-2 EERO process (one SSRO stage with two stages in CMCR: one nanofiltration (NF) stage followed by one terminal RO stage), then validated the model using performance data obtained from commercial RO projection software. Retentate recycle ratio was one of the key parameters to determine energy efficiency of EERO. In addition, the implementation of NF membranes in the first stage of CMCR yielded additional improvement in EERO performance and played an important role in determining optimum salt rejection. An optimal design of the NF stage was successfully achieved by hybridization of different NF membranes in a vessel (internally staged design, ISD). Under the conditions optimized, EERO exhibited not only greater energy efficiency (3–25%), but lower concentration polarization (CP) and potentials of membrane fouling than conventional SSRO for ≥55% overall recoveries because of reduced water flux in the lead elements (averagely 34%). These findings can thus provide insight into optimal design and operation of the EERO process.NRF (Natl Research Foundation, S’pore)Accepted versio

Phosphorus uptake, partitioning and redistribution during grain filling in rice

BACKGROUNDS AND AIMS: In cultivated rice, phosphorus (P) in grains originates from two possible sources, namely exogenous (post-flowering root P uptake from soil) or endogenous (P remobilization from vegetative parts) sources. This study investigates P partitioning and remobilization in rice plants throughout grain filling to resolve contributions of P sources to grain P levels in rice. METHODS: Rice plants (Oryza sativa \u27IR64\u27) were grown under P-sufficient or P-deficient conditions in the field and in hydroponics. Post-flowering uptake, partitioning and re-partitioning of P was investigated by quantifying tissue P levels over the grain filling period in the field conditions, and by employing (33)P isotope as a tracer in the hydroponic study. KEY RESULTS: Post-flowering P uptake represented 40-70 % of the aerial plant P accumulation at maturity. The panicle was the main P sink in all studies, and the amount of P potentially remobilized from vegetative tissues to the panicle during grain filling was around 20 % of the total aerial P measured at flowering. In hydroponics, less than 20 % of the P tracer taken up at 9 d after flowering (DAF) was found in the above-ground tissues at 14 DAF and half of it was partitioned to the panicle in both P treatments. CONCLUSIONS: The results demonstrate that P uptake from the soil during grain filling is a critical contributor to the P content in grains in irrigated rice. The P tracer study suggests that the mechanism of P loading into grains involves little direct transfer of post-flowering P uptake to the grain but rather substantial mobilization of P that was previously taken up and stored in vegetative tissues

Physically-assisted removal of organic fouling by osmotic backwashing coupled with chemical cleaning

Membrane filtration is a robust water treatment method against membrane fouling driven by natural organic matters for drinking water production and wastewater reclamation. Despite recent studies revealing that osmotic backwashing (OBW) can effectively remove organic fouling from the membrane, the mechanism of fouling removal and the supportive effect of OBW remains unexplored. Here, we performed a comparative analysis of chemical cleaning and OBW-assisted chemical cleaning to remove organic fouling from the reverse osmosis membrane. Natural organic matters such as humic acid, sodium alginate, and tannic acid were used as model foulants. Various in-situ monitoring and ex-situ characterization methods were used to evaluate direct and in-direct effects on membrane cleaning. Using OBW increased the water permeability coefficient of the fouled membrane compared to using chemical cleaning solely, improving the water flux up to 10.8%. Notably, in-situ monitoring revealed that pore generation below the fouling layer readily dissociated the fouling layer and helped the cleaning agent encounter foulants rapidly. The characterization of the fouled membrane demonstrated that applying OBW before chemical cleaning could enhance the membrane cleaning efficiency

The knowns and unknowns of phosphorus loading into grains, and implications for phosphorus efficiency in cropping systems

Inefficient use of phosphorus (P) in agriculture adds to production costs, increases the risk of eutrophication of waterways, and contributes to the rapid depletion of the world’s non-renewable rock phosphate supplies. The removal of large quantities of P from fields in harvested grains is a major driver in the global P cycle, but opportunities exist to reduce the amount of P in harvested grains through plant breeding. Using rice (Oryza sativa L.) as a model crop, we examine our current understanding of the process of P loading into grain and its regulation by genetic and environmental factors. We expose a dearth of knowledge on the physiological processes involved in loading P into grains, poor resolution of the genes and networks involved in P mobilization from vegetative tissues to grains, and limited understanding of genetic versus environmental contributions to variation in grain P concentrations observed among genotypes. We discuss potential breeding strategies and highlight key research gaps that should be addressed to facilitate these breeding approaches. Given the strong economic and environmental incentives for a low grain P trait, we suggest that some of the investment and resources currently directed to determining the molecular regulation of P starvation responses in model plant species should be diverted to resolving the physiology, genetics, and molecular regulation of P loading into cereal grains

Simultaneous dechlorination and disinfection using vacuum UV irradiation for SWRO process

The dechlorination effectiveness of ultraviolet (UV) irradiation and its effects on marine biofilm community were investigated in a pilot-scale seawater reverse osmosis (SWRO) process. Lab-scale feasibility tests were conducted for three sources of low-pressure UV (LPUV), vacuum UV (VUV) and medium-pressure UV (MPUV) lamps. As a result, a VUV lamp was chosen for the pilot process because this lamp ensured efficient dechlorination in raw seawater at UV dose < 700 mJ/cm(2). In a pilot plant test, the VUV irradiation successfully dechlorinated the seawater without damaging the reverse osmosis membrane. The VUV irradiation decreased the bacterial diversity of biofilm community. The results indicate that simultaneous dechlorination and disinfection were successfully achieved using VUV irradiation for SWRO. Therefore, the VUV irradiation can be used as an alternative dechlorination strategy in SWRO. This paper also provides the niche information of the UV-resistant microbial community; this information may be useful to guide the disinfection strategy further. (C) 2016 Published by Elsevier B.V