Tsuyoshi Imai

Yamaguchi University · Graduate School of Science and Engineering

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...

A novel thermotolerant caproic acid-producing bacterial strain, Clostridium M1NH, was successfully isolated from sewage sludge. Ethanol and acetic acid at a molar ratio of 4:1 proved to be the optimal substrates, yielding a maximum caproic acid production of 3.5 g/L. Clostridium M1NH exhibited remarkable tolerance to high concentrations of ethanol...

Anaerobic digestion (AD) technology is a viable solution to the challenges attributed to sewage sludge, but its specific impact on biogas production and the dynamics of methanogenic bacteria has not been widely understood. This research investigated the effects of shifts in AD operational temperatures on microbial communities and biogas production....

This study aimed to evaluate the two-stage and one-stage anaerobic co-digestion of vinasse and spent brewer yeast cells (SBY) for biohydrogen and methane production. Optimization of the vinasse-to-SBY ratio and fly ash concentration of the two-stage and one-stage production processes was investigated. In the two-stage process, the vinasse-to-SBY ra...

Thermotolerant caproic acid-producing bacteria were isolated from sewage sludge and evaluated for caproic acid production with various substrates. The ethanol-acetate was the most efficient substrate for enriched culture, with 2.7 g/L caproic acid and a yield of 47%. Clostridium strain M1NH was isolated from enriched culture and identified as a gra...

Thermotolerant caproic acid-producing bacteria were isolated from sewage sludge and evaluated for caproic acid production with various substrates. The ethanol-acetate was the most efficient substrate for enriched culture, with 2.7 g/L caproic acid and a yield of 47%. Clostridium strain M1NH was isolated from enriched culture and identified as a gra...

Upper mesophilic temperature acclimation of halophilic, hydrogen-producing bacteria from salt fields was investigated in this study, along with the changes in microbial abundance during an-aerobic digestion (AD) process. Genomic approaches such as PCR-denaturing gradient gel elec-trophoresis (DGGE) and next-generation sequencing (NGS) were performe...

The transition to renewable energy sources is crucial to ensure a sustainable future. Although the sugar and ethanol industries benefit from this transition, there are untapped opportunities to utilize the waste generated from the sugar and ethanol process chains through two-stage anaerobic digestion (TSAD). This review comprehensively discusses th...

Temperature plays a significant role in anaerobic digestion (AD) as it affects the microbial communities and ultimately controls the efficiency of the process. Few studies have looked at temperature-adjusted AD, but it is unclear how the temperature shifts affect biogas production and the dynamics of microorganisms involved in methanogenesis. This...

This study aims to demonstrate the effectiveness of using biological oxidation for hydrogen sulfide (H2S) control. A long-term experiment was conducted using a rod-shaped electrode made of highly conductive concrete, which provided an electron pathway for H2S mitigation. Bacterial flora analysis was conducted using PCR-DGGE and metagenomic analysis...

Providing effective and sustainable water disinfection methods, without harmful by-products, is essential to protect public health and safety. It is hypothesized that the application of liquid-thin-film (LTF) technology can enhance the bactericidal activity of both ultraviolet (UV) irradiation and ozone (O3) treatments. Therefore, this study aimed...

When biogas is produced, the liquid anaerobic digestion effluents (LADE) still contain pollutants. Struvite precipitation is a technique for reducing pollutants as well as recovering useful elements such as nitrogen, phosphorus, and magnesium. This study aims to precipitate struvite from LADE and use it as an additive to palm oil mill effluent (POM...

Localized biogenic corrosion and extrication of annoying odors caused by hydrogen sulfide (H2S) have long been a big problem in the management of urban sewer systems. H2S emission control in sewers via chemically or biologically normal oxidation processes has also been investigated extensively and is costly. The objective of this work was to develo...

This study aimed to enhance dark fermentative hydrogen production from co-digestion of distillery wastewater (DW) and glycerol waste (GW) through integration with microbial electrolysis cells. First, the optimal proportion of DW and GW in hydrogen production was investigated in batch mode. The results show that DW and GW co-digestion at a ratio of...

Operating temperature significantly affects biogas output, process stability, and microbial communities involved in anaerobic digestion. There are several unanswered questions regarding how microbial communities adapt in correlation with biogas production performance, especially when a digester fails to maintain thermophilic conditions. In this stu...

This study aims to create a quantitative polymerase chain reaction (q-PCR) methodology for monitoring the hydrogen-producing mixed cultures enriched from elephant dung using alpha-cellulose as a carbon source through five generations of repetitive sub-culture. The enriched thermophilic mixed cultures from the fifth cultivation cycle gave the highes...

This study determined the optimal conditions for the deep eutectic solvent (DES) pretreatment of sugarcane leaves and the best fermentation mode for hydrogen and methane production from DES-pretreated sugarcane leaves. Choline chloride (ChCl):monoethanolamine (MEA) is the most effective solvent for removing lignin from sugarcane leaves. The optimum...

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...

In wastewater treatment plants (WWTP), anaerobic digester (AD) units are commonly operated under mesophilic and thermophilic conditions. In some cases, during the dry season, maintaining a stable temperature in the digester requires additional power to operate a conditioning system. Without proper conditioning systems, methanogens are vulnerable to...

The disadvantages of the air–cathode single-chamber microbial fuel cell (AC-SCMFC) performance can be caused by numerous factors, and retention time (RT) is one such factor. It is difficult to conclude the ideal RT run for the specific tests under the same conditions. To determine the optimum RT for various types of microbial fuel cell (MFC), an AC...

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...

Global phosphorus scarcity implies the importance of phosphorus recovery. Desorption is an essential process in phosphate removal by adsorption technique by enabling two crucial aspects: the reusability of adsorbent and the recovery of phosphorus. In this study, phosphate desorption by NaOH for composite reusability and phosphorus recovery by CaCl...

One of the important factors in enhancing the performance of microbial fuel cells (MFCs) is reactor design and configuration. Therefore, this study was conducted to evaluate the regressors and their operating parameters affecting the double anode chamber-designed dual-chamber microbial fuel cell (DAC-DCMFC) performance. Its primary design consists...

The objective of this study was to verify the feasibility of using biochar, functionalized with layered double hydroxides, as a fertilizer after its use in phosphate treatment (P-BC-LDHs). It was conducted with several levels of P-BC-LDHs using seed germination and early growth assays of lettuce (Lactuca sativa L.). The application of P-BC-LDHs res...

Extreme halophiles offer the advantage to save on the costs of sterilization and water for biohydrogen production from lignocellulosic waste after the pretreatment process with their ability to withstand extreme salt concentrations. This study identifies the dominant hydrogen-producing genera and species among the acclimatized, extremely halotolera...

BACKGROUND AND OBJECTIVES: Fixed-bed column has been considered an industrially feasible technique for phosphate removal from water. Besides the adsorption capacity, the effectiveness of an adsorbent is also determined by its reusability efficiency. In this study, phosphate removal by a synthesized amorphous zirconium (hydr)oxide/MgFe layered doubl...

The goal of this study was to evaluate the use of expanded clay as a support material for Thermoanaerobacterium thermosaccharolyticum KKU19 to produce hydrogen from oil palm trunk hydrolysate (OPT) and slaughterhouse wastewater (SHW) in a fixed-bed reactor (FBR) under non-sterile conditions. The effects of hydraulic retention time (HRT) on the perf...

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...

Seed germination and early growth assays of lettuce (Lactuca sativa L.) were used as means in the evaluation of different dosage performances of P-loaded layered double hydroxides (P-LDHs). Of these two experiments, results from the former showed that P-LDH application at lower concentrations (0.5 and 1.0 g) influenced the slightly delayed germinat...

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...

Extremely halotolerant hydrogen-producing bacteria were investigated, owing to their ability to live in high salinity conditions. Based on this characteristic, it was hypothesized that extremely halophilic hydrogen-producing bacteria can tolerate high concentrations of Na⁺ ions. To test this hypothesis, we investigated the characteristics of extrem...

This study was conducted to compare between leachate and mixed waste produced electricity as one of the performance parameters of Compost Solid Phase Microbial Fuel Cells (CSMFCs) besides complying with compost requirements. Mixed waste as solid-phase produced from composting has higher potency to obtain electricity than leachate as the liquid phas...

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...

The objective of this study is to reveal the evidence of hydrogen sulfide (H2S) control by biological oxidation through conducting the long-term experiment of H2S mitigation by providing electron pathway with highly conductive concrete and bacterial flora analysis of electricity-producing bacteria. The long-term experiment of H2S mitigation by biol...

The objective of this study is to reduce the production of Hydrogen sulfide (H 2 S) in sewer pipe by using conductive concrete and electricity-producing bacteria (EPB). This work was mainly focused on evaluating the effect of inoculation of EPB isolated from sewage sludge from municipal wastewater treatment plant for decreasing production of H 2 S....

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...

In this study, rice straw-derived biochar was used as a raw material for the synthesis of biochar functionalized with layered double hydroxides (BC-LDHs) as efficacious phosphate adsorbents. Many types of BC-LDH composites were successfully fabricated by either the precipitation of layered double hydroxides on pristine biochar or the pyrolysis of f...

An air-water interface generator is a proposed apparatus aiming to enhance oxygen transfer by increasing the contact area between air and water. It has been proved that this apparatus could increase the volumetric oxygen transfer coefficient in laboratory scale. Therefore, it is important to study about upscaling in order to apply this apparatus in...

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...

The new approach in this study was using electric induction technique to enhance soil fertility of bare land in a combination of rabbit urine application in the form of liquid fertilizer. This approach had been exaggerating soil microbial activities and modifying the exchange capacity of anions and cations in soil. This study aimed to find out the...

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...

The optimum conditions for biohydrogen production from glucose with extremely halophilic bacteria from Samut Sakhon salt pan, Thailand were identified. The extremely halophilic bacteria's ability to produce hydrogen in nearly saturated NaCl concentration provides a potential benefit of cutting the cost of water and sterilization in dark fermentatio...

The final objective of this study is to develop highly conductive concrete which effectively mitigates the concentration of hydrogen sulfide (H2S) in sewer pipe. In the first part of this study, using electricity-producing bacteria (EPB) isolated from sewage sludge from a municipal wastewater treatment plant, the influence of inoculation of these E...

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...

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...

The sulfate-reducing bacteria (SRB) consortium (Desulfovibrio sp. Desulfitibacter sp. Dethiosulfatibacter sp. and Clostridium sp.) was investigated for sulfate removal and biohythane production from rubber sheet wastewater (RSW). The RSW at COD/SO42− ratio of 13 and pH 6 was suitable for sulfate reduction and biohythane production. Hydrogen yield,...

In this current study, an apparatus called air-water interface generator was investigated for oxygen transfer enhancement by increasing a contact area between air and water. The effect of this apparatus and its optimal installation condition were investigated. The total volumetric oxygen transfer coefficient (kLaT) in this study was divided into vo...

Batch and continuous modes for bio-hydrogen production by co-digesting cassava starch wastewater with buffalo dung were investigated. Response surface methodology with central composite design was used to optimize the bio-hydrogen production conditions. A hydrogen production potential of 1787 mL H 2 /L was achieved under optimal conditions of 2.84...

Nitrogen is the most abundant element in the atmosphere, however, most often deficient in agricultural lands. This research was an exploratory to get indigenous non-symbiotic nitrogen-fixing bacteria. Soil samples were collectedfrom rhizosphere of green beans. This study was aimed to determine the bacterial population of the three regions; screenin...

The objective of this study was to develop a new technology to mitigate the concentration of hydrogen sulfide in sewer pipe by using conductive concrete. Experimental results showed that the concentration of hydrogen sulfide significantly decreased by using conductive concrete, and the effectiveness lasted during 66 days experiment. Also found was...

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...

This research aims calculate the potency of rainwater harvesting as an alternative source of freshwater on the rural areas of wetlands of Indonesia on dry season (May-October), under the effect of climatic event such as El Nino. The study area is the area of ex-Mega Rice Project areas of Central Kalimantan, Indonesia. Daily rainfall data 1990-2004...

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...

Residual Chlorella sp. biomass obtained after anaerobic solid-state fermentation was used to produce bio-hythane. The residual biomass was pretreated using acid, thermal, and acid-thermal methods before their respective hydrolysates were used in dark fermentation followed by the methanogenesis of anaerobic digestion to produce hydrogen and methane,...

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...

Extremely halotolerant hydrogen-producing bacteria were investigated, owing to their ability to live in high-salinity conditions. Based on this characteristic, it was hypothesized that extremely halotolerant hydrogen-producing bacteria can tolerate high concentrations of Na⁺ ions. To test this hypothesis, we investigated the characteristics of extr...

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...

The effect of glycerol waste (GW) concentration was studied in anaerobic co-digestion with canned sardine wastewater (CSW), has been examined using the 1-stage mesophilic (P1), 1-stage thermophilic (P2) and 2-stage mesophilic (P3) process. P3 process was the best process, could improve the biogas production (bio-hythane) in the case of canned sardi...

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...

This study aimed to enhance hydrogen production from sugarcane syrup by biogas sparging. Two-stage continuous stirred tank reactor (CSTR) and upflow anaerobic sludge blanket (UASB) reactor were used to produce hydrogen and methane, respectively. Biogas produced from the UASB was used to sparge into the CSTR. Results indicated that sparging with bio...

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...

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...

There is increasing concern that conventional disinfection methods present several disadvantages, namely hazardous by-products (chlorine, ozone), high cost, complicated setup and high maintenance (UV, membrane, advanced oxidation process). Latest technologies of water disinfection must be developed from exploiting the advantages of conventional met...

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...