Corrosion on piping under thermal insulation is localized corrosion and a problem for plants which are located near the sea shore. Thermal insulation offers a corrosive environment where chloride ions allow concentration and humidity is high by penetrating rain water or splashes from the sea containing chloride ions to the insulation. A visual inspection can detect the corrosion after removing the insulator. However, removing and restoring the insulation needs enormous time and troubles. Therefore, a method for identifying the corrosion without removing the insulation is required. An acoustic emission (AE) method can detect elastic waves emitted by fractures of corrosion product (rust). In this study, AE monitoring was applied to evaluate the corrosion volume on a steel plate in high humidity with MgCl₂ solution. AE activity increased with time from several days later after providing MgCl₂ solution and then decreased. AE activity became high again after providing MgCl₂ solution. While AE activity was high, the thickness of the plate on the corrosion drastically changed. When the thickness did not change, externally low AE activity was detected. The relation between corrosion volume and cumulative AE count from the corrosion showed different linear relation in the early and following stages.

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For membrane pretreatment of seawater reverse osmosis desalination, the degradation of the membrane performance by biofouling is a serious problem. Chitosan hydrogel membranes including silver, which are inorganic antibacterial reagents, were fabricated for the antibacterial activity enhancement of a separation membrane. They were prepared using two methods: the immersion method and the mixture method. We investigated the effects of a membrane preparation method on membrane properties, water permeability and antibacterial activity. We analyzed the obtained membrane with Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), thermogravimetry-differential thermal analysis (TG-DTA). It was found that the hydrogel membrane prepared by the mixture method contained silver particles. On the other hand, the hydrogel membrane prepared using the immersion method contained silver in ion form. The water content of the membrane decreased with increase of the silver content, and the water flux increased with increase of the water content. In addition, we evaluated antibacterial activity of the hydrogel membrane by the conductance method. The chitosan/silver hydrogel membranes showed a distinctive inhibitory effect for growth of Escherichia coli and Staphylococcus aureus. The chitosan/silver hydrogel membranes prepared using to immersion method showed strong antibacterial activity compared with that prepared by the mixture method.

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For the removal of radioactive strontium dissolved in seawater in the harbor near the Fukushima Daiichi Nuclear Power Plant, two kinds of sodium-titanate (ST) -impregnated fiber were prepared by means of radiation-induced graft polymerization and subsequent chemical modifications: one was ST-impregnated fiber, or SSS-ST fiber, originating from cation-exchange fiber that was prepared by grafting sodium styrene sulfonate (SSS) onto a 6-nylon fiber, and the other was DMAEMA-ST fiber originating from anion-exchange fiber prepared by grafting dimethylaminoethyl methacrylate (DMAEMA) onto 6-nylon fiber. In a batch adsorption mode, these ST-impregnated fibers exhibited a higher removal rate of strontium in seawater than commercially available ST adsorbent (SrTreat) in a granulous form. At a mass ratio of seawater to fiber of 100, the percentages for the removal of strontium were 86 ％ and 83 ％ for the SSS-ST and DMAEMA fibers, respectively. From the viewpoint of endurance against alkaline conditions in the preparation scheme, the SSS-ST fiber was judged to be feasible for practical use.

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To calculate forward osmosis (FO) hollow fiber membrane performance driven by osmotic pressure gradient, we developed a model based on both internal concentration polarization (ICP) and dilution in lumen side of the hollow fiber membrane. Comparison between experimental data and simulated results showed good agreement for the water flux and the final concentration of the diluted draw solution (DS) using intrinsic membrane parameters (water permeability of 0.227 LMH/bar, salt permeability of 0.035 LMH and structural parameter of 900 μm). Based on this model, the local permeate flux and local DS concentration inside the FO module were calculated. This study offers knowledge for process optimization and membrane design in large-scale FO operation by hollow fiber membrane modules.

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This study evaluated the fouling of a forward osmosis membrane in a pressure retarded osmosis (PRO) system using Aldrich humic acid (AHA) as a model foulant. Fouling behaviour was evaluated quantitatively by observation of the decline in water permeability in the fouling tests: when AHA and CaCl₂ were added to the feed solution (FS), severe fouling (51 ％ decline) occurred; when only AHA was added to FS, moderate fouling (23 ％ decline) occurred. Photographs of the membrane surfaces after fouling tests indicate that the severe fouling is due to the formation of a dense layer of cross-lined AHAs with Ca^2＋ on the membrane surface of the FS side.

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