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Publications (213)
Unmanned aerial vehicle (UAV)-based photogrammetry that employs structure from motion (SfM) and multi-view stereo (MVS) has been widely used in many disciplines, particularly in topographic surveying. However, several factors can affect the accuracy and precision of these techniques, including the analysis settings of the SfM process. In this study...
Little were certain about how wastewater treatment plants (WWTPs) affected the Japanese riverine microplastic contamination. This study explored the influences of WWTPs on microplastic pollution, assessed ecological risks, and looked at the sources-to-sinks phenomenon (WWTPs-to-rivers-to-marine) in riverine settings in Japan’s Yamaguchi prefecture....
Due to a lack of proper sanitation services, the disposal of residential wastewater from slum areas has become one of the river pollution contributors. In Yogyakarta slums were concentrated along the riverbanks of the Winongo, Code and Gajahwong rivers. Due to slum upgrading, slums have declined from 264.5 ha to 114.72 ha between 2016 and 2020. Thi...
Microplastics (MPs) pollution has become an escalating problem in Bangladesh due to its rapid urbanization, economic growth, and excessive uses of plastics, however data of MPs pollution of fresh water resources is very limited in Bangladesh. This study investigated microplastics pollution in the riverbed sediments in the peripheral rivers of Dhaka...
To obtain the spatial distribution of the spatial high-resolution habitat suitability I (HSI) of horseshoe crab larvae, we used a UAV equipped with a multispectral camera to estimate the bathymetric distribution of intertidal areas on tidal flats that are not inhabited by horseshoe crabs. We also proposed RBI, which estimates mud volume from the B...
In Yamaguchi Bay, where horseshoe crabs inhabit, a population survey is conducted every year to determine their population density. The problems of surveying larval horseshoe crab populations are that mudflats are difficult to walk on, require many people, the efficiency of finding individuals varies depending on the skill of the surveyor, and the...
Cropland suitability analysis is a crucial process for achieving the optimum utilization of land use. It is frequently used today and continues to develop, especially in the methods. Digital soil mapping is a new technique that can generate spatial predictions of soil attributes obtained from digital soil covariates, reducing the cost, time, and la...
Environmental DNA (eDNA) analysis is becoming widespread to reduce the effort for fish survey in fish friendly river works. However, the sampling method for obtaining a representative sample in cross-section, and eDNA flow-down distance are unknown. In this study, by performing metabarcoding analysis at 6 points per one cross-section, sampling meth...
Microplastic pollution in small-scale river sediments remains mostly unknown. This study explored microplastics in the sediments of four small-scale Japanese rivers in Yamaguchi Prefecture: the Awano, Ayaragi, Asa, and Majime. Sediment samples (n = 23) were collected from the selected stations. Density separation and wet peroxidation methods were a...
Digital soil mapping using hyperscale modeling of topographic parameters is a promising approach to capture the multiscale relationship between soil properties and the landscape. Hyperscale analysis sampled and calculated topographic parameters at more than one resolution. This study aims to develop prediction models for estimating the soil particl...
Freshwater microplastics pollution has been a recent focus. River freshwater microplastics pollution are vital towards freshwater ecosystems as well as have been the prominent source-to-sink conduits to export MPs into the marine realm. Wastewater treatment plants (WWTPs) have been identified as one of the major point-sources. To date, sources-to-s...
Although different treatment techniques have been developed to eliminate phosphorus contamination, including for wastewater treatment, treated water often fails to meet quality regulations. Amorphous-ZrO2/Mg-Fe layered double hydroxide (LDH) composites with different molar ratios (Zr:Fe = 1.5–2) were prepared in two-stage synthesis by the combinati...
Rivers are vital for understanding freshwater microplastics pollution, along with the conduits from land-sources to marine-sinks. In this study, we investigated microplastics in the small-scale Awano and Ayaragi rivers, which flow into the Sea of Japan (SJ), and the Asa and Majime rivers, which flow into the Seto Inland Sea (SIS) in Yamaguchi Prefe...
This study aimed at screening salt-tolerant phosphorus (P) accumulating organisms (PAOs) and investigating the P release and uptake of the organisms in saline wastewater. Batch experiments were conducted over 98 days in solutions with a salinity of 3.5% and P concentrations of 1, 5, 10, and 20 mg-P/L. The P-uptake ability of microorganisms increase...
Mapping flood physical vulnerability is spatially limited because it requires input data such as building structures and materials, which are unavailable on large spatial scales. In this study, we propose a new method for qualitatively evaluating the flood vulnerability of residential areas in the context of the exposure and resilience to flood haz...
We estimated the performance of river fish habitat evaluation using width-to-depth ratio (WDR) in comparison with eco-environmental diversity (EED) to propose an inexpensive and easy-to-use habitat evaluation procedure, which is applicable to small river construction works. WDR calculation costs less than that of EED. For verification, 25 stations...
Marine microplastics pollution has been a global emerging threat. Rivers have been identified as the major transporting pathways of microplastics from land sources into marine environments. This study investigated microplastics in the two rivers i.e. Awano River (AR) and Majime River (MR) which are flowing into the Sea of Japan (SJ) and the Seto In...
Marine microplastics pollution has been an emerging global threat. This study investigated microplastics pollution in the ‘Seto Inland Sea (SIS)’ and ‘Sea of Japan (SJ)’ surrounded Yamaguchi prefecture areas in Japan. The density separation method was applied to extract microplastics from sea surface sediment and water samples. Polymeric compounds...
In small and medium-sized rivers, deterioration of landscape and water flow capacity due to overgrowth of vegetation such as reeds are problems. Vegetation control by hydraulic factors is not easy. In this study, we focused on the solar radiation as a factor of controlling overgrowth. According to the solar shading experiment on a reed overgrowing...
Marine microplastics pollution has been the global cause of concern currently. This study investigated marine microplastics pollution in the selected areas of Yamaguchi prefecture, Japan. Density separation methods were used to extract microplastics from sediment and water samples. Polymeric compounds were identified through ATR-FTIR analysis. The...
Despite attaining the Millennium Development Goal water target on "access to improved water sources", Bangladesh is lagging the new Sustainable Development Goal target for "safely managed drinking water services". Sufferings are mainly prevalent in many pockets of hazard-prone hard-to-reach (HtR) areas. This study aims at the development of a house...
Marine microplastics pollution has been the emerging global threat currently. This study investigated microplastics pollution in the Seto Inland Sea and the Sea of Japan surrounding Yamaguchi prefecture areas in Japan. Density separation methods were used to extract microplastics from sea surface sediment and water samples. Polymeric compositions w...
For appropriate evaluation of environmental odours, it is necessary to develop a reliable odour measurement scale. Odour intensity reflects people’s perception of odours and contributes to effective odour management. In this study, Japanese conventional six-point odour intensity scale was reconsidered to ensure equal intervals between odour intensi...
With tap water as a physical solvent to absorb CO2 from different concentrations of mixed gases (containing CO2 and N2), an apparatus outfitted with a water-film generator was used to enhance the CO2 dissolution rate as well as the contact between the liquid and gas phases. The operational pressure in the absorption tank, induced gas pressure, init...
This research uses tap water to absorb carbon dioxide from mixed gas (N2 and CO2) in an absorption apparatus coupled with a water-film-forming-unit (WFFU). The objective is to assess the benefits of using a WFFU to enhance CO2 removal efficiency at low pressure conditions. Based on our results, the WFFU significantly improves CO2 capture at 0.30 MP...
The recent development of Structure‐from‐Motion (SfM) and Multi‐View Stereo (MVS) photogrammetry techniques has enabled semi‐automatic high‐resolution bathymetry using aerial images taken by consumer‐grade digital cameras mounted on unmanned aerial vehicles (UAVs). However, the applicability of these techniques is sometimes limited by sun and sky r...
A previous study by the present authors identified nutrients necessary for hydrogen production,
which was enhanced by using casamino acids (CAAs) as a nitrogen source. However, CAAs are costly;
accordingly, using algal waste substrates with different nutrient compositions was speculated to serve as an
alternative strategy for increasing hydrogen pr...
Aerial photogrammetry for tidal flat was carried out at about 5 m high with a camera attached with an APS-C digital camera at the end of a pole with a total length of 7.5 m. It became clear that it was distributed. We can estimate the suction distribution of the sandbar occurred on the tidal flats from the relation between the specific height of th...
Lyzenga's multispectral bathymetry formula has attracted considerable interest due to its simplicity. However, there has been little discussion of the effect that variation in optical conditions and bottom types—which commonly appears in coral reef environments—has on this formula's results. The present paper evaluates Lyzenga's multispectral bathy...
The ability of Clostridium butyricum RAK25832 to use casamino acids as a nitrogen source was investigated. Strain RAK25832 showed the capacity to utilize different types of carbon sources. With glucose as a carbon source (10 g/L), the preferred final concentration of casamino acids was 26.67 g/L, with a cumulative hydrogen production, production ra...
The applicability of EmporeTM styrene-divinylbenzene reverse-phase sulfonated (SDB-RPS) passive sampler disks for integrative sampling of organic chemicals in river water was investigated to evaluate toxicity levels via bioassay using larval medaka (Oryzias latipes). Those disks were deployed for periods of 1, 2, 3, 7, and 10 days (PS different per...
This paper presents the results from using a physical absorption process to absorb gaseous CO2 mixed with N2 using water by producing tiny bubbles via a liquid-film-forming device (LFFD) that improves the solubility of CO2 in water. The influence of various parameters—pressure, initial CO2 concentration, gas-to-liquid ratios, and temperature—on the...
River toxicity based on acute toxicity to Medaka fish and chemical concentrations measured using a gas chromatography–mass spectrometry simultaneous analysis database were investigated. Between June 2012 and January 2014, 21 samples were collected from three rivers in Japan that have most of their catchments in residential areas. Toxicity tends to...
In Dili, the capital city of Timor-Leste, water pollution is rapidly getting worse. This study aims to reveal a pollutant discharge mechanism and to propose a feasible water quality preservation measure even at the citizen level. Water quality survey and water level survey at 13 wells and 16 streams in four watersheds were conducted. As a result, t...
Coastal erosion is proceeding on the northern coast of Bengkalis Island, Riau Province, Indonesia. Lands where erosion is progressing are primarily peatlands. In the northern coast of Bengkalis Island where erosion speed is high, bog bursts were discovered. In the Meranti Islands, Indonesia, peatland collapses like bog bursts were also seen. Compar...
Dili is the capital city of Timor-Leste and has the highest population comparing to other cities. The quality of fresh water streams in Dili was evaluated using the larval himedaka acute toxicity assay combined with active sampling. Ten liters of grab water samples were collected from the Fatuhada, Campo Alor, Caicoli, and Kuluhun streams, filtered...
We have developed a rapid measurement method to the paper disc groundwater velocity meter which uses no electricity. The paper disc groundwater velocimeter can measure the groundwater velocity and direction in one borehole using the trajectory of the ink transported by the groundwater water on the paper disc. The smallest measurement time of this d...
This study investigated the effect of combined treatments using pressurized carbon dioxide (PCD) and sodium hypochlorite (NaOCl) on the inactivation of Enterococcus sp. in artificial seawater. Bacterial inactivation was conducted in a liquid-film-forming apparatus with various pressure conditions, CO2 supply rates, and chlorine dosages. Combined PC...
This study identified the performance of Lyzenga water column correction under controlled condition of noise, water quality, and bottom type diversity. We build a simulated multispectral imagery, represent the subsurface reflectance of coral reef environment that receives by Worldview-2 satellite. The evaluation was performed to two different subsu...
In empirical approach, the satellite-derived bathymetry (SDB) is usually derived from a linear regression. However, the depth variable in surface reflectance has a more complex relation. In this paper, a methodology was introduced using a nonlinear regression of Random Forest (RF) algorithm for SDB in shallow coral reef water. Worldview-2 satellite...
Until now, Indonesia only had a single large-scale bathymetry map (1:250.000) for the entire nation and detailed maps (1:50.000 or 1:25.000) of a few locations. A straightforward and cost-efficient bathymetry mapping of the Indonesian coral reef is urgently needed. To address this problem, we present a generalized multispectral bathymetry estimatio...
In Shinto Yamaguchi Prefecture Iwakuni, steel-making slag of different chemical and physical properties were put into the waters, the varification of the algal bed substratum formed were carried out. The purpose of this study was to carry out the verification of the fish-gathering effect, which its seaweed function creates an irregularity shape to...
Interest is growing in a disinfection technique for water treatment without disinfection byproducts. This study presents the result of using a liquid-film-forming apparatus at less than 1.0 MPa for disinfection of seawater. The sensitivity of Enterococcus sp. (ATCC 202155) to the pressurized carbon dioxide (CO2) was examined under various condition...
Ship ballast water should be disinfected before being discharged into the ocean to avoid the dispersal of non-native species into the marine environment. This study presents the results of using pressurized carbon dioxide (CO2) at less than 1.0 MPa for inactivating Escherichia coli and Enterococcus sp. in artificial seawater (3.4% salinity). The ba...
This research proposes “Eco-Environmental Diversity index (EED)”, which calculates environmental diversity of depth, velocity, bed condition, and vegetation within fish home range. To incorporate fish preference information into EED, environmental parameters are categorized to represent suitable habitat for different behavioral modes like feeding a...
Various groundwater velocimeters were developed to measure groundwater flow. However, those conventional velocimeters need electricity as well as high cost. Our objective was to develop the low cost and unplugged groundwater velocimeter. In this study, single dot type paper disk groundwater velocimeter was tested. Calibration of the velocimeter was...
Our previous research suggested that the entrance selection of a multiple path fishway affects migration success ratio. In this research, firstly, we prove that entrance selection affect migration success through field experiment. Secondly, we determine suitability index for air bubble condition, which were 0.27 for no bubble, 0.88 for surface bubb...
In the palm oil mill effluent (POME) discharged during the production process of palm oil, oil is contained in the emulsion state. Currently, the open ponding system (facultative/anaerobic lagoons) is being applied as the main treatment method for POME owing to low operating costs. However, the main disadvantages of this system are the requirement...
Enzymatic hydrolysis is an essential step in the fermentative H2 production process of lignocellulosic biomass to convert cellulose and hemicellulose into fermentable sugars. The waste from disposable wooden chopsticks (DWC) was represented as wood waste and investigated in this study. In order to optimize the condition of the enzymatic hydrolysis...
Water sounds are believed to be important in triggering the upriver ascent behavior of migratory fish species. Modeling the effect of underwater sound on fish preference represents a promising technique to determine migratory paths for the comprehensive analysis of river habitat suitability. In this study, we aimed to determine the preference and w...
A stone-embedded fish passage (SEF) allows fish to pass a barrier by reducing the velocity in the slope. The efficiency of SEFs has however not been evaluated well and the design parameters are not clear. The efficiency of SEFs for fish therefore needs to be evaluated and analyzed. In this research, we attempted to develop a simple equation to esti...
Wastewater may contain high levels of the nutrients: nitrogen and phosphorus. Excessive release of nutrients to the environment can cause severe environmental problem such as eutrophication leading to algal blooms, oxygen deficiency, and fish kills. The forward osmosis (FO) could be a choice of treatment. FO process presents the results of using fo...
Chlorination is the most common method used for disinfection of drinking water. However, growing concerns about the potential hazards of disinfection by-products have emerged many efforts to develop alternative disinfection methods. In this study, a new disinfection method was developed using low-dose chlorine in combination with a high level of wa...
Field investigations on wastewater quality and odor emissions at a potato starch factory were conducted from July 2007 to May 2008. Odor index of decanter effluent and separator effluent in penetration ponds ranged from 43 to 51, suggesting that anaerobic decomposition of wastewater with high concentration of organic matters especially in decanter...
The objective of this study is evaluate algal bed substratum by steel-making slag. We carried out construction of algal bed substratum by steel-making slag that of particle size finer than natural rock. When algal bed substratum was constructed, the value of the turbidity and pH was almost the same as the surrounding sea area. It could not be confi...
Erosion area, volume and particulate organic carbon emission to the ocean were calculated by the coastal erosion of the Bengkalis Island, Indonesia. In the Bengkalis Island, total of 741 ha peatland has lost from 1998 to 2013. The erosion rate of the coast is almost double in recent 5 years. Annual total of 2.6 Mm3 of the peat and 1.2 Mm3 of the cl...
The effect of different carbon source on the efficiency of enhanced biological phosphorus removal (EBPR) from synthetic wastewater with acetate and two ratios of acetate/starch as a carbon source was investigated. Three pressurized pure oxygen sequencing batch reactor (POSBR) experiments were operated. The reactors (POSBR1, POSBR2 and POSBR3) were...
A granular calcined Mg-3-Fe LDH adsorbent was prepared by using co-precipitation method under low super saturation condition. The characteristic of the adsorbent was analyzed by powder X-ray diffraction (XRD) and scanning electron microscope (SEM). The continuous phosphate adsorption experiments were conducted in a glass fix-bed column. The results...
Although visible bands of high-resolution multispectral imagery are used for bathymetry, the relative utility of different bands is poorly understood. Therefore, we evaluated the relative utility of the six visible bands of WorldView-2. We statistically selected the visible bands that gave the best accuracy under different situations, tallying how...
The purpose of this study isto show the relationship between an ordinal scale toxicity index LT50-1 and a ratio scale toxicity index LDR50. One water sample per site was taken during June-December 2012, between 9AM-12PM with the assumption that household waste was released. Based on the results, minimum 2-3 grades of LT50-1 value is needed to obtai...
The inactivation effects of pressurized CO2 against bacteriophage Qβ and ΦX174 were investigated under the pressure of 0.3–0.9 MPa, initial concentration of 107–109 PFU/mL, and temperature of 17.8°C–27.2°C. The optimum conditions were found to be 0.7 MPa and an exposure time of 25 min. Under identical treatment conditions, a greater than 3.3-log red...
The use of filamentous fungi in bioremediation of heavy metal contamination has been developed recently. This research aims to observe the capability of filamentous fungi isolated from forest soil for bioremediation of mercury contamination in a substrate. Six fungal strains were selected based on their capability to grow in 25 mg/L Hg2+-contaminat...
Hydrogen (H2) production from lignocellulosic materials may be enhanced by removing lignin and increasing the porosity of the material prior to enzymatic hydrolysis. Alkaline pretreatment conditions, used to delignify disposable wooden chopsticks (DWC) waste, were investigated. The effects of NaOH concentration, temperature and retention time were...
Lyzenga’s method is used widely for radiative transfer analysis because of its simplicity of application to cases of shallow-water coral reef ecosystems with limited information of water properties. WorldView-2 imagery has been used previously to study bottom-type identification in shallow-water coral reef habitats. However, this is the first time...
Coral reef habitat mapping contained information of stratum types is a fundamental component of ecosystem-based management because it integrates a variety of information to define the extent, nature and health of ecosystem. Field survey identifications in comparison with remote sensing approach are time consuming, labour intensive, high cost and no...
The newly developed groundwater velocimeter which uses paper and ink was applied to the observation of the movement of the groundwater in the coastal sand bar on September, 2013. This measurement method uses tailings of the eluted dots on the paper. As a result of revising the analytical methods of the tailings of the paper, we could measure ground...
Stones embedded fishway in Fushino river is highly appreciated as an good example of inexpensive small scale restoration works. However, its efficiency on fish migration and/or designing parameters of the same type of fishway are not clear enough. To examine the migration efficiency of the fishway, we released Ayu (Plecoglossus Altivelis Altivelis)...
Irrigation water and recycled water used for farm gardens can be a potential source of contamination of
microbial pathogens that cause harmful illness. This study investigated the use of pressurized carbon dioxide to inhibit pathogens in water sources. An apparatus producing microbubbles was operated with pressure up to 0.7 MPa, room temperature an...
Phytoremediation has been widely used for wastewater treatment technology. Horsetail was investigated for its capacity to remediate lead and chromium in leachate. This plant seemed to be an effective choice for phytoremediation due to its survival in extreme to moderate conditions, the availability of annual or perennial varieties and a deep root s...
This study investigated the potential application of pressurized CO2 for water disinfection. Under supporting high pressure, a high volume of CO2 microbubbles were produced in a liquid environment. Specifically, the inactivation effects of CO2 against Escherichia coli, bacteriophage MS2 and T4 were examined at equal pressures (0.3 - 0.9 MPa) and te...
Multispectral satellite remote sensing can predict shallow-water depth distribution inexpensively and exhaustively, but it requires many in situ measurements for calibration. To extend its feasibility, we improved a recently developed technique, for the first time, to obtain a generalized predictor of depth. We used six WorldView-2 images and obtai...
Dependence on salinity of settling rates of estuarine suspended sediment (The Chikugo River) and coastal suspended sediment (Ariake sea sediment) were studied. Two sediment samples had same mode particle size of the fine particles. As a result of the study, we clarified that the estuarine suspended sediment settled faster than the coastal sediment...
In the coastal areas of Bangladesh, scarcity of drinking water is acute as freshwater aquifers are not available at suitable depths and surface water is highly saline. Households are mainly dependent on rainwater harvesting, pond sand filters and pond water for drinking purposes. Thus, individuals in these areas often suffer from waterborne disease...
Irrigation water and recycled water used for farm gardens can be a potential source of contamination of microbial pathogens that cause harmful illness. This study investigated the use of pressurized carbon dioxide to inhibit pathogens in water sources. An apparatus producing microbubbles was operated with pressure up to 0.7 MPa, room temperature an...
In the coastal areas of Bangladesh, scarcity of drinking water is acute as the fresh water aquifers at reasonable depths are not available and surface water is highly saline. Households are mainly dependent on rainwater harvesting, pond sand filter (PSF), and rain-fed pond water for drinking purposes. To ascertain the water quality for human consum...
Based on the production of gas bubbles with the support of a liquid film-forming apparatus, a device inducing contact between gas and water was used to inactivate pathogens for water disinfection. In this study, the inactivation effect of CO2 against Escherichia coli was investigated and compared with the effects of N2O and N2 under the same pressu...