Tadashi Hibino

• Hiroshima University

This study presents the development and application of a fuel-cell-type (FCT) sensor to monitor seabed levels in sandy and cohesive sediment environments. The FCT sensor, which utilizes dissolved oxygen as a fuel, enables sensitive bathymetry monitoring via a spontaneous electric current. Laboratory experiments demonstrated that the current, intern...

Approximately 300,000 tons of waste oyster shells (OS) are generated annually in the Republic of Korea. Comprehensive research is required on the effects of OS on coastal environments for direct application of OS. This study aimed to investigate the physicochemical property changes in coastal sediments caused by the application of calcined OS. OS w...

Background: Carbon nanotubes (CNT) are promising material as cathode modifier in sediment microbial fuel cells (SMFC). The use of binders to bind CNT to electrode surfaces can hinder adsorption capacity, conductivity and thermal stability. This study utilizes a binder-free technique of CNT-implanted carbon cloth (CC-CNT) and carbon felt (CF-CNT) to...

In coastal areas, organic matter (biogenic organic matter) produced and decomposed by plants, benthic animals and other organisms (biological activity) is deposited as bottom sediment. The elemental composition of organic matter in bottom sediments varies in a complex manner depending on biological activity, and understanding this variation may lea...

It is expected to promote ecological activity by increasing sand diameter particles with increasing complexity on tidal flats created using GCA. In this study, we investigated the effects of GCA on the ecological regeneration of reductive tidal flats (tidal flats constructed with GCA) where organic sludge from sewage systems (oil and grease, etc.)...

The application of dredged sediment is required to supply nutrients into the construction of artificial tidal flats.Several previous studies demonstrated that Granulated Coal Ash (GCA) -induced changes in the physicochemical properties of tidal flats promoted the supply of nutrients in coastal sediments. The purpose of this study was to investigate...

A 4,000 m2 steel slag (SS) bed was constructed in the brackish water area for water quality remediation in 2017. This study demonstrates the ability of SS to stimulate carbon sequestration based on one-year pilot and in situ SS beds. The pilot SS bed increased the soil organic matter (SOM) content by 5.1 wt. %, sequestering sewage-derived organic c...

Highlights •Seasonal DO characteristics in eutrophic water was predicted using machine learning. •Capacitive potential was critical variable to predict seasonal hypoxia. •CP enhanced hypoxia prediction using conventional water quality variables. •Combination of CP sensor and ML is efficient hedge against hypoxia disasters.

Because it is assumed that the dredged mud, which is material for tidal flat construction, will not diffuse into seawater, the organic properties of dredged mud have not been studied. In this study, dredged mud was collected in columnar form from two tidal flats with different elapsed times of dredged mud input, and the organic properties of each d...

In the combustion method, a method for measuring the fixed amount of organic matter in organic mud, organic matter is classified into readily degradable and persistent organic matter using the combustion temperature (300°C) as an indicator. The coordination and desorption of organic matter to metal ions (persistent and per-decomposable organic matt...

The mortality rate of Pacific oysters cultivated in Hiroshima Bay has consistently remained elevated. Various factors, including elevated water temperature, decreased salinity, competition with other organisms, and depletion of oxygen from bottom sediments, have been proposed as potential causes of the oyster mortality. However, a definitive cause...

Effects of granulated coal ash (GCA) on coastal sediments have been estimated to be (1) humification, (2) granulation of clay particles, and (3) polymerization and saponification of fatty acids. However, these effects have not yet been demonstrated through chemical analysis. In this study, analytical procedures were proposed to verify these effects...

Sediment quality of riverbank tidal flats was investigated before and after the covering of granulated coal ash (GCA). This study focused on the formation of recalcitrant organic carbon by GCA, and n-hexane extraction, fatty acid analysis, and combustion tests were carried out. The results showed that extraction of more fatty acids than oils and fa...

Artificial tidal flats made of granulated coal ash(GCA) have been created in Hirosima coastal area and the effect of GCA on tidal flats environment has been evaluated. In previous research, we clarified the improvement of the sediment and biological environment in tidal flats with high organic mud deposits. In this study, we investigated the enviro...

Carbon neutralization is a global issue that needs to be implemented immediately, but the use of energy resource is not fully explored. In this study, we examine the carbon negative resources that can be used in the coastal areas as a tool for realizing carbon neutral ports. Deterioration of coastal water environment is mainly due to long-term accu...

Oxidation-reduction potential (ORP) measures energy level of redox reactions in solution, and can be used as qualitative index to evaluate water quality in tidal flats with high biological activity. Conventional ORP sensors measure activity of ions that have passed through a membrane with internal electrodes, thus continuous monitoring at field is...

Machine-learning-based models are used to predict dissolved oxygen (DO); however, acquiring continuous water quality data for input variables in harsh environments remains challenging. Herein, redox potential (ORP) determined by a thermo-treated flexible carbon fiber electrode was introduced as a single or preferential input variable for machine-le...

The voltage variation of in situ sediment microbial fuel cells with the sedimentary environment hinders their practical applications. In this study, an iron substrate that provides equal cell voltage output regardless of the sedimentary environment, was used to elucidate the electron-transfer-mediating characteristics of soil organic matter. The ce...

In the loss on ignition test, the combustion temperature and duration are largely different among researchers. It is necessary to clarify the changes in the IL (value of loss on ignition) owing to combustion temperature and duration for comparing the IL measured under different conditions. In this study, we compared the IL, obtained from the loss o...

Since bottom hypoxic water is result of redox reaction between reducing substances diffused from bottom sediment and dissolved oxygen, hypoxia can be detected by measuring redox potential. Indoor experiments confirmed response of potential according to concentration of dissolved oxygen and reducing substance. In addition, the potential was measured...

Three types of elution experiments were conducted on granulated coal ash (GCA) covered on revetment affected by waves and currents, and structures of cement hydrates such as calcium silicate hydrate (CSH) and CaSO4 that compose GCA were estimated. In the elution experiments, an elution tendency of ions from GCA in salt water, deion-ized water, and...

Reduction problem represented by hypoxia is a typical water pollution that appears in closed sea areas, but accurate and continuous monitoring method has not been established due to technical and economic difficulties. In this study, we investigated a new water quality monitoring system using redox potential. A carbon electrode was more reactive an...

In order to understand the material cycle in the tidal flat ecosystem and the effect of granulated coal ash (GCA) on improving the tidal flat environment, the artificial tidal flats made of GCA were created. Sedimentary mud and benthic organisms in the tidal flats were continuously investigated for 2.5 years. It was been observed that algae and ben...

In the tidal flats and the shoals which constructed gradually by using the dredged mud for 8 years, the features of the topographical change under and after construction and the habitat conditions of the organisms such as the short-neck clams were grasped from the existing data and the field survey. According to the result of evaluation of the topo...

Sediment Microbial Fuel Cells (SMFC) is a device that converts the reduced enrgy of sediment into electric power. SS-SMFC, which is a mixure of steel slag (SS) and sediment, has high power generation capacity. On the other hand, SS-SMFC has not been put into practical use because the current processing capacity of the cathode is the rate-determing...

In order to quantify the blue carbon effect, continuous measurement of CO2 in the field is desired. Redox potential in seawater changes greatly due to the dissolution of CO2, but it also changes significantly due to dissolved oxygen (DO) consumption. In this study, we investigated the redox reaction associated with the dissolution of CO2 and the DO...

Carbon fixation by marine plants such as eelgrass has been the main focus of research on the blue carbon effect in coastal areas. In this study, we collected organic sediment from the seafloor with excessive organic matter and conducted experiments on the persistent degradation of organic matter by coal ash granules (GCA). The results suggested tha...

Granulated coal ash (GCA) is a strong in-situ capping material for removing PO 4-P and H 2 S-S in contaminated coastal sediments. Although GCA performance is weakened by sediment deposition, related research is rare. To evaluate sediment deposition effects on PO 4-P and H 2 S-S removal by GCA, GCA was placed on the top of sediment (C-GCA), was part...

Hypoxia is a long-standing environmental problem in coastal areas worldwide, but technical and economic difficulties impede accurate and continuous spatiotemporal monitoring. This study aims to monitor seasonal hypoxia dynamics at high-resolution by developing a novel capacitive potentiometric sensor. The underlying hypothesis of this study was tha...

A granulated coal ash (GCA) eluting ions such as Ca²⁺, SiO2, OH⁻ were covered on riverbank tidal flats. In this study, polymerization process of organic matter owing to GCA was verified. Sediment properties were investigated for 27 months after GCA capping. An increase in pH caused increase in coarse particles and decrease in fine particles. The gr...

The DLVO theory using the potential energy around the deposited sediment particles is defined by the sum of the intermolecular energy of the particles and the electrostatic repulsion energy. Thus, we hypothesised that if the surface potential of the bottom sediment particles is measured, the shear stress of the bottom sediment can be evaluated. In...

In coastal areas where the production of short-necked clams is significantly decreasing, a new tidal flat construction method using dredged mud is required to construct a tidal flat that improves the production. The development of new utilization technology is desired. In this study, the effectiveness of dredged mud utilization was evaluated from s...

A nano zero-valent iron (NZVI) was added into sediments to enhance the capacities of sediment microbial fuel cells (SMFCs) for pollutant removal and electricity generation. Open and closed circuits were applied to confirm the impact of NZVI on the pollutant removal performance of SMFCs. The operation of SMFCs in a closed circuit with 0.06% NZVI pro...

Steel slag was employed as an additional substrate for power generation in sediment microbial fuel cells (SMFCs), and its role in the degradation of recalcitrant organic matter and sediment remediation was investigated. Steel slag improved the degradation of soil organic matter (SOM) in SMFC by 69 % compared to an individual SMFC with a 6.3-times h...

In recent years, decline in clams production has become a problem in many coastal areas. Creation of an artificial tidal flat using dredged sediment has been proposed to solve this problem, but settling of clams in the artificial tidal flat remains uncertainties. The purpose of this study is to create a habitat for clams using dredged sediment cove...

The critical shear stress of the sediment is an important parameter that determines the transportation of the sediment. However, it is difficult to carry out experiments on a large number of samples because a large-scale experimental device and a large number of samples are required to measure the critical shear stress of the sediment. On the other...

Thermogravimetric and differential thermal analysis (TG-DTA) has been widely used for identifying the thermal reaction characteristics such as oxidation, thermal decomposition and dehydration.However, the measurement conditions are not unified, and it is necessary to determine the optimum measurement conditions for sediment. In this study, we condu...

In order to reduce the volume of dredged sludge and sewage sludge, we investigated a method to reduce the water retention of sediment by focusing on adsorbed cations. Moreover, we attempted to classify the cation adsorption site due to understand the sites where monovalent cations are easily adsorbed. Method of adsorbed cation capacity (CEC) is dif...

In order to purify the river sedimentary mud that releases odors, we investigated and analyzed the soil properties and chemical properties of sedimentary mud, and conducted indoor experiments. The purpose of this study is to clarify the organic properties of the sedimentary mud, which is the origin of odors, and to confirm the effect of GCA sprayin...

This study focus on the long-term improvement effect of sediment and water quality using granulated coal ash as sand covering material. To understand the effect, a field experiment and a laboratory experiment of the same scale and same time were conducted to compare the amount of sediment deposition, the ion concentration of pore water, and the cha...

Steel-slag was added as a catalytic material of redox reaction to sediment microbial fuel cells (SMFCs) in an in situ sediment biodegradation experiment to determine its benefits in the long-term power production of the cells and to elucidate the external factors affecting power production. The steel-slag was found to consistently increase the powe...

Artificial tidal flat utilizing dredged sediment have been developed and the case studies to show its effectiveness have been reported. However, it is hardly to say that the artificial tidal flat has solved the problem of the decreasing in catch of asari clam in these days. It is desired to develop new technology of high puroduct of asari clam usin...

Oligotrophy in coastal areas is considered to be the main cause of deterioration in aquatic product productivity, this can lead to a decrease in algae growth capacity. In this study, we investigated how to create aquatic environment in which algae, especially diatoms, can grow in oligotrophic condition. The effect of GCA (Granulated Coal Ash) on di...

It is said that the poverty of iron supplied to the coastal areas contributes to the decrease in marine products. The concentration of iron in natural water is low, and it is difficult to clarify the role of iron locally. In this study, an experiment was conducted to develop an iron elution device that uses a microbial fuel cell to elute a sufficie...

Widespread pollutants from wastewater are serious threats to the ecosystem and aquatic environments in harbor areas. However, very few methods are available for the remediation of contaminated sediments. Herein we examine an in-situ method using a new material, known as slaked lime–fly ash–cement mixture (SFCM), that removes phosphate and hydrogen...

Shallow bottom was constructed by using granulated coal ash (GCA) as a material in the inner harbor where benthic organisms can not live due to the influx of organic matter from sewage.Based on thesurvey results of benthic animals for about 3 years on the tidal flat implemented in advance, the condition of animal regeneration in the shallow bottom...

Global warming and eutrophication caused by human activity and variations in social needs for foods have been deteriorated environments of oyster farm. Various surveys in response to environmental contaminations have not yet been conducted sufficiently, because aquaculture technology has been developed mainly with emphasis on the quality and increa...

A granulated coal ash (GCA) was scattered onto organically-enriched tidal flats deposited along the Kyobashi River flowing through the center of Hiroshima City. It has been observed that the GCA layer is improving the ecosystem by forming algae that feed on benthic animals. In this study, major microalgae that flourished in the GCA layer were ident...

Recently, sediment treatments via electrochemical methods have been paid attention. In this paper, removal mechanisms of nutrient salts and hydrogen sulfide (H2S) via an electrokenetic method, and the factors that impact the performance of electrokenetic method are reviewed. Furthermore, field experiments were conducted to confirm the removal rates...

This study deals with sediment microbial fuel cell (SMFC) as a technique for purifying (reducing suppression) sediment by obtaining electric power from organically-enriched sediment in coastal areas. Other studies have shown that performance of SMFC is strongly dependent on the efficiency of consuming electrons harvested from anode to cathode. In t...

Ages sediment (acidification, reduction) inhibits the inhabiting of organisms in the coastal area where minerals are lacking. Effect of combustion ash elute minerals have a very important role in the activity of organisms, and it was possible to confirm reproduction of benthic organisms by scattering GCA (granulated coal ash) on ages sediment. Coal...

It is confirmed that property of the deposited organic mud on the tidal flat with granulated coal ash (GCA) changes, it is suggested that they are related to microorganisms attached to GCA. However, It is not clarified relationship between GCA and effects. In this study, the relationship between microorganisms and tidal flat sediment environment wa...

The discharge of untreated wastewater into a water body strongly deteriorates the benthic habitat environment of bottom sediment. In this study, field experiments were conducted in the Fukuyama inner harbor (Hiroshima, Japan), which is exposed to large amounts of untreated domestic wastewater discharge. The water quality in this harbor is seriously...

Granulate coal ash (GCA) has been widely used for improving both sediment and water environments in littoral regions. Dissolved ions from GCA have been pointed out to play an important role in the improvements of sediment and water environments. As the dissolution characteristics of a material in solvent depend on the solvent characteristics, this...

Applying sediment microbial fuel cells (SMFCs) into sediment can remediate the sediment; however, nutrient salts cannot be removed by SMFCs effectively. In this study, sediment mixed with steel-making slag is used a fuel in SMFCs for understanding the potential of steel-making slag in nutrient salt removal in SMFCs. To the best of our knowledge, no...

In order to investigate the applicability of granulated coal ash (GCA), a by-product of coal thermal power stations, to freshwater lakes, two incubation experiments (fall and summer experiments) were conducted using large-volume vessels and sediments taken from eutrophic lakes. The phosphorus and nitrogen release fluxes in the vessels with GCA (up...

In Nihonbashi River in urban area, sludge will accumulated on the riverbed. The sludge is anaerobically decomposed, reduction, and acidification of the organic matter will proceed. Reducing sediment is the key of deterioration of the water environment because it causes hypoxia and sulfur hydride. In this study, the effect of improving water and sed...

In this study, the field tests were performed by applying ferronickel slag (FNS) and granulated coal ash (GCA) to artificial tidal flats, and corresponding ecosystem functions were quantitatively evaluated. The result of field test revealed that sediment quality and biota corresponding to FNS were observed to be similar to those of sand. In contras...

Steel slag and granulated coal ash (GCA) have been widely used to cover bottom sediment for improving sediment and water quality. The effects of these materials on removing nutrient salts and restoring biological environment have been repoted previously. However, according to our best knowledge, decomposition mechanisms of organic matter in the lay...

Reduced substances in sediment diffuse into bottom water and react with dissolved oxygen (DO), resulting in the formation of hypoxic bottom water. Thus, it enables to monitor the formation of hypoxic water (DO consumption) via the measurement of electrode potential in the sea water. In this study, reaction characteristics between reduced substances...

Sediment microbial fuel cell (SMFC) can remediate sediments along with electricity generation; however, the SMFC performance is below the level for practical use. In this study, field experiments and laboratory experiments are conducted to evaluate the performance of SMFC when steel slag-mixed sediment is used as a fuel (SS-SMFC). Anode electrode w...

Excess deposition of organic mud aggravates tidal flat and sea bottom environment. Chemical effect of sediment is important to consider the deposition characteristics of sediment. In this study, we focused on the influence of adsorbed cations of sediment, solute and ionic strength in solution on settling velocity of interface and water retention of...

Showa drainage pipe flowing into Nakagawa-river of the Tone River water system is a tidal water channel affected by the tidal fluctuations from Tokyo Bay, and exposed to domestic wastewater discharge from the surrounding residential area. This results in large accumulations of organic-enriched sediment at the bottom of the water channel. Thus, high...

Hydrogen peroxide treatment is often carried out for reducing the amount of organic substances. However, there are many unclear points on method and the principle of decomposing organic matter for sediment containing various organic substances. In this study, hydrogen peroxide treatment and a method of changing the combustion temperature of the sam...

To restore the water environment in the Pasig River and its tributaries, field observations were conducted for elucidating the characteristics of the water quality. Besides, The Pasig River is one of the organic contaminants-enriched rivers, and the inflow of untreated wastewater causes several serious environmental problems, such as eutrophication...

Variation of groundwater level and quality in the Ota River delta are affected by sea water and continental groundwater. To understand water circulation between river water and groundwater, variation factors of groundwater level and quality was discussed since 1970 to 2010. Moreover, variation of river water quality varied with groundwater level va...

Excess deposition of sediment aggravate tidal flat and sea bottom environment. To consider the resuspension of sediment, it is important to clarify the factor of critical shear strength change. In this study, we focused on liquid limit related with shear strength. Considering cohesion and repulsion force of sediment based on DLVO theory, ionic stre...

Differential thermal analysis (TG-DTA) has been widely used for identifying the organic matter characteristics of sediment; however, different methods of TG-DTA have been conducted. This study aims to propose the method of TG-DTA for the analysis of littoral sediment. Namely, methods of sample pretreatments (i.e drying and sieving), optimum heating...

Understanding organic matter characteristics (e.g., amount and state) of sediments is necessary for evaluating both the sediment and water environments; however, methods that have been proposed to investigate these characteristics are relatively expensive. This study attempted to evaluate the organic matter characteristics of littoral sediments by...

The growth of phyto and animal benthos in Fukuyama inner harbor is inhibited because of the discharge of untreated wastewater into the harbor. Field experiments and benthos observations are conducted to examine the restoration processes of ecosystem in the harbor. When gravel was used as the basement, the reduced level of the basement was evaded, l...

Granulated coal ash (GCA) is an alkaline material made from fly ash, which mainly comprised of SiO2, Al2O3, and CaO. It has been reported that scattering GCA on sea bottom sediment can suppress the release of nutrient salts from the sediment into bottom water. This study is aiming at revealing mechanisms of phosphate immobilization by GCA through l...

The Pasig River is the main river in Metro Manila, Philippines that connects Laguna de Bay with Manila bay. Due to lack of a proper sewage system, its 47 tributaries and creeks are contaminated by untreated sewage water. This paper sumarisez the characteristics and issues of the Pasig river tributaries. This study shows that BOD and COD of the Este...

Benthos cannot survive in strongly reduced sediments, in which the redox potential is around −400 mV. Such sediments are typically found in inner harbors that are exposed to wastewater discharges. Field experiments were conducted to investigate the potential of sediment microbial fuel cells (SMFCs) for improving the benthic environment in such sedi...

Nakashita, S.; Nakamoto, K.; Koshikawa, Y.; Kim, K.-H., and Hibino, T., 2017. Evaluation of granulated coal ash as artificial seabed for eelgrass. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 40–44. Coconut Creek (Florida...

The method of improving bottom water environment using industrial wastes to suppress diffusion substances from bottom sediment has recently captured the attention of many researchers. In this study, wastewater discharge-derived sediment was used to examine an alternative approach involving the use of sediment microbial fuel cells (SMFCs) in relaxin...

Deposition rate of sludge on the riverbank of the Kyobashi river (a branch river of the Ota river) is about 1 cm per year, leading to the large amounts of sludge on the riverbank which exacerbate both substratum and water environments of the river. To date, we have proposed some methods using granulated coal ash (GCA), which is alkaline granulated...

Sediment microbial fuel cells (SMFCs) can remediate sediment that vanish water environment, in concurrence with electricity generation. Unfortunately, power produced by SMFCs is still low because of energy losses (overvoltage) such as activation loss and mass transfer loss, which weaken the practical use of SMFCs. In this study, we proposed some me...

Anaerobic digestion in organic matter-enriched sediment forms a strong reduced environment which inhibits benthos living. Here, we aim at examining the growth and type transition of algae in a strong reduced sediment through field experiments. We supplied electron acceptors to the sediment to lower the reduced condition of the sediment. The supplyi...

To clarify the applicability of recycled resources as ground material on a pro-environmental seawall, we conducted the verification test that covered the sediment with a ferronickel slag (FNS) and a granulated coal ash (GCA) at the pro-environmental seawall. In this study, we focused on the characteristics of FNS and GCA as habitat for manila clam...

Soil particle surface has negatively charge. Characteristics of organic mud change with adsorption of cation and organic matter has been reported. Understanding of transport and deposition of organic mud, we proposed a new measuring method of adsorption ion of organic mud. Moreover, we cleared that liquid limit varies because of the changing the ty...

Sediment microbial fuel cell (SMFC) can improve decomposition of organic matter in sediments; however, there are some problems such as low rate of electron transfer and decrease in pH of sediments. In this study, we aim to understand effects of granulated coal ash (GCA) on increasing electron transfer rate, increasing pH, and fixing nutrient salts...

Sediment microbial fuel cell (SMFC) can improve decomposition of organic matter in sediments; however, there are some problems such as low rate of electron transfer and decrease in pH of sediments. In this study, Effects of steel slag on increasing electron transfer rate, increasing pH, and fixing nutrient salts in SMFC were examined through labora...