Journal of Water and Environment Technology
Online ISSN : 1348-2165
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Original Articles
  • Mayumi Suzuki, Tomohiro Kose, Hitoshi Tamaki, Kuniaki Kawata
    Type: Original Article
    Volume 16 (2018) Issue 1 Pages 1-17
    Released: February 10, 2018
    JOURNALS FREE ACCESS

    A tsunami generated by The Great East Japan Earthquake inundated 3.1 − 5.4 km inland of the low-lying coastal areas of the Tohoku district, Japan, leaving sand and silt deposits over parts of the inundated areas. Applying cluster analysis to the deposits to ascertain their heavy metal compositions, we tried to estimate the tsunami deposit origin and attempted to ascertain their characteristics and distribution based on the shoreline topography and the land use of the backland. Cluster analysis results revealed that most tsunami deposits have similar metal compositions to those of marine sediments. The results suggest dominant marine sediment origin. The tsunami deposits showing soil origin of a unique location were subjected to strong tsunami waves because of the topography of surrounding areas. Moreover, a unique location around a building that disturbed the tsunami wave water currents showed soil origin. The silt contents in tsunami deposits were influenced by differences in tsunami wave water currents attributable to differences in shoreline topography. The metal compositions of tsunami deposits reflected both the mineralogical characteristics of the sediment and pollution profiles of the backland land use.

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  • Keerthi Katam, Kota Maetani, Toshiyuki Shimizu, Jun Nakajima, Debraj B ...
    Type: Original Article
    Volume 16 (2018) Issue 1 Pages 18-29
    Released: February 10, 2018
    JOURNALS FREE ACCESS

    Consumption of detergents containing linear alkyl benzene sulfonate (LAS) and fluorescent whitening agents (FWAs) is increasing rapidly in Asian countries. A respirometric oxygen uptake method was conducted to examine the aerobic biodegradability of some of the commercially available laundry and dishwashing detergents of India, Japan, Indonesia, and Thailand. Indian detergents and Japanese detergents showed 95–100% of LAS removal. However, the three-dimensional fluorescent spectra results indicated the presence of residual metabolites such as sulfophenyl carbonate. Indonesian detergents and Thai detergents showed less LAS removal, but the progress of benzene ring cleavage of LAS in these detergents was observed from the test results. The FWAs were observed mainly in laundry detergents. The removal of FWAs during biodegradation test was observed to be between 12.4 and 78.8%. The complex changes in oxygen uptake curve during the test period suggested the presence of various organic compounds in the detergents. The tested detergents were classified into three clusters based on the relationship between the total organic carbon and the fluorescence (220/290 nm) removals. The diverse biodegradation results among the tested detergents from different Asian countries suggested the effects of various ingredients present in the detergents.

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  • Hitoshi Tamaki, Daisuke Muraoka, Tetsunori Inoue
    Type: Original Article
    Volume 16 (2018) Issue 1 Pages 30-39
    Released: February 10, 2018
    JOURNALS FREE ACCESS

    Effect of water disturbance on grazing by the sea urchin with the refuge habitat was estimated. We tested the hypothesis that sea urchins ceased feeding and remained in refuge habitat for protection against disturbance even though water flows were not high to inhibit their grazing. Fecal density from sea urchins was positively related to their residence time under the undisturbed condition. This result suggested that the fecal density is a useful criterion for understanding the residence time of sea urchins in the calm condition. Five types of structure (L-shaped, cave shaped, crack-shaped, smaller and larger rectangular structure) as refuge habitats were deployed in the undisturbed tank with sea urchins and the fecal densities at each structure were measured to examine the habitat forms which sea urchins prefer. This experiment indicated that the crack-shaped form was used for sea urchins as the refuge habitat. Feeding rate of sea urchins inversely corresponded to water flow. Feeding rates with the refuge habitat were lower than in the absence of habitat, although water disturbances were almost the same. The presence of refuge habitat seemed to be a factor responsible for the reduction of their grazing, because sea urchins sheltered to avoid water disturbances.

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  • Phuc-Nguon Hong, Chanreaksmey Taing, Phuong-Thanh Phan, Ryo Honda
    Type: Original Article
    Volume 16 (2018) Issue 1 Pages 40-53
    Released: February 10, 2018
    JOURNALS FREE ACCESS

    Extracellular polymeric substances (EPS) are reported to be the major foulant in membrane bioreactor (MBR) processes. It is important to understand the EPS fractions which cause irreversible fouling to reduce operation cost and energy consumption in MBR. In this study, we developed polarity-molecular weight profiling, in which EPS components were plotted on two-dimensional matrix of its polarity and molecular weight, and applied it to investigate EPS of bulk sludge and cake layers from a lab-scale MBR. The EPS components were also characterized via three-dimensional excitation-emission matrix (3D-EEM) spectroscopy. The result showed that hydrophilic substances as large as 100 − 670 kDa was found only in loosely-bound EPS (LB-EPS) of bulk sludge but not in that of cake layers nor in permeate. Hydrophobic substances smaller than 20 kDa were mainly found in soluble microbial products (SMP) in bulk sludge. Hydrophilic substances larger than 670 kDa was mainly found in tightly-bound EPS (TB-EPS) of bulk sludge and in LB- and TB-EPS of cake layers. These findings suggest that, after conditioning of micropores of virgin membrane by hydrophobic substances smaller than 20 kDa in SMP, hydrophilic biopolymers as large as 100 − 670 kDa in bulk sludge clog the narrowed micropores inside membrane, causing irreversible fouling.

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  • Nobuyuki Katagiri, Mitsunobu Takatsu, Satoshi Kitahata, Yuki Mizuno, E ...
    Type: Original Article
    Volume 16 (2018) Issue 1 Pages 54-62
    Released: February 10, 2018
    JOURNALS FREE ACCESS

    A novel enzymatic membrane bioreactor system using the non-purified culture supernatant of white-rot fungus Trametes versicolor was developed to perform decolorization of dye wastewater. The culture supernatant was periodically obtained from fungal cultures cultivated in cost-effective natural medium, which uses blackstrap molasses typically present in food waste, by gravitational sedimentation. The model dye wastewater containing an anthraquinone type dye and the supernatant exhibiting dye decolorization activity were mixed in a continuous stirred tank membrane reactor with an ultrafiltration membrane that permitted enzyme recycling in the reactor. The results obtained from the enzymatic membrane bioreactor showed that approximately 80% of decolorization and approximately constant permeation resistance were maintained for a few days of continuous treatment. Furthermore, decolorization behaviors were well described using a combined equation based on mass balance for continuous stirred tank membrane reactor and kinetics of enzymatic decolorization of the dye.

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  • Mokhtar Guizani, Takeru Maeda, Ryusei Ito, Naoyuki Funamizu
    Type: Original Article
    Volume 16 (2018) Issue 1 Pages 63-71
    Released: February 10, 2018
    JOURNALS FREE ACCESS

    Synthesis of magnetic nanoparticles (MNPs) attracted the interest of many researchers for many applications. Among the applications of interest is their potential use as a draw solution in forward osmosis owing to their ease of recovery and surface-area-to-volume ratio. Such a draw solution is expected to generate high osmotic pressure. However, for such an application, the choice of coating material is a crucial parameter which is still poorly understood. In this paper, we tested three different coating materials with different properties (molecular weight and hydrophobicity) to better understand their effect on the properties (ability to generate flux, dispersion, magnetic properties, recovery, etc.) of coated MNPs. Magnetic nanoparticles were prepared using co-precipitation method. Various coating materials were used in this study, namely dextran 40,000, oleic acid and polyethylene glycol 2,000 and 4,000. Magnetite co-precipitation and nanoparticle coating were carried out simultaneously. The coated nanoparticles were characterized using scanning electron microscope, X-ray Powder Diffraction, coating ratio, and osmotic pressure and flux generation. Findings indicate that in order to suppress aggregation and generate osmotic pressure, coating material should have low molecular weight and feature a hydrophilic property.

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