Takaya Higuchi

A model for membrane bioreactor process based on the concept of formation and degradation of soluble microbial products.

A mathematical model of soluble microbial products (SMPs) formation-degradation was established based on the activated sludge model no. 1 and was applied to the membrane bioreactor process with high concentration of activated sludge under intermittent aerobic operational condition. The simulation results were in good agreement with the experimental data which indicated that the coefficients used in the model could successfully describe the treatment performance. The most advantage of this modified model over the conventional one was that the significant importance of SMP existence was demonstrated and the model provided an reasonable comprehension for SMP concept. The present study demonstrated that SMPs contributed most to the organic matter in the effluent, and the results coincided well with the observations of many other researchers.

Effect of Enforced Aeration on In-Vessel Food Waste Composting

A laboratory composting was conducted to determine the effect of the continuously enforced aeration on the composting performance. The mixture of dog food, excess sludge, and woodchip was used as raw composting materials. The temperature changes in the decomposition process, and pH, weight loss, ash, and extract composition from the final product after 17 days composting were investigated. The results demonstrated that flow rate of enforced aeration indeed influenced the composting performance. Composting under 0.05-0.1 l min−1 condition seemed better than that under 0.2-0.4 l min−1 condition. Higher flow rate of air not only cooled the composting mixture significantly, further adversely affected temperature rise, but also evaporated moisture mostly. Thermophilic composting can occur under 0.05-–0.1 l min−1 air flow rate condition, while composting in cases of 0.2-0.4 l min−1 air flow rate mainly resulted in a mesophilic process. Microbial activity was considered to be significantly inhibited at 0.4 l min−1 air flow rate condition based on the analyses of total organic carbon and volatile fatty acids from water extraction of composting products.

Potential bioremediation of mercury-contaminated substrate using filamentous fungi isolated from forest soil

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 Hg(2+)-contaminated potato dextrose agar plates. Fungal strain KRP1 showed the highest ratio of growth diameter, 0.831, thus was chosen for further observation. Identification based on colony and cell morphology carried out by 18S rRNA analysis gave a 98% match to Aspergillus flavus strain KRP1. The fungal characteristics in mercury(II) contamination such as range of optimum pH, optimum temperature and tolerance level were 5.5-7 and 25-35°C and 100 mg/L respectively. The concentration of mercury in the media affected fungal growth during lag phases. The capability of the fungal strain to remove the mercury(II) contaminant was evaluated in 100 mL sterile 10 mg/L Hg(2+)-contaminated potato dextrose broth media in 250 mL Erlenmeyer flasks inoculated with 10(8) spore/mL fungal spore suspension and incubation at 30°C for 7 days. The mercury(II) utilization was observed for flasks shaken in a 130 r/min orbital shaker (shaken) and non-shaken flasks (static) treatments. Flasks containing contaminated media with no fungal spores were also provided as control. All treatments were done in triplicate. The strain was able to remove 97.50% and 98.73% mercury from shaken and static systems respectively. A. flavus strain KRP1 seems to have potential use in bioremediation of aqueous substrates containing mercury(II) through a biosorption mechanism.

Simulation of fish behavior and mortality in hypoxic water in an enclosed bay

A model of fish preference for environmental conditions (dissolved oxygen (DO) and water temperature) and mortality was developed and coded within a combined hydrothermal and eutrophication model. The model was applied to an enclosed bay located in the western part of Japan, where eutrophication and associated onset of hypoxia at the bottom waters would occur in every summer. A field survey of fish behavior under hypoxic and non-hypoxic waters was conducted by releasing marbled sale in the bay and tracked its movement. At the same time, vertical profiles of DO, salinity and water temperature were measured at every 0.5m vertical interval at several locations along the tracking path of fish. Moreover, a series of preference tests for DO, salinity and temperature in the laboratory were conducted in order to decide preference parameters of fish. The model could simulate reasonably the observed behavior and movement of the fish under both hypoxic and non-hypoxic waters in the bay; thereby, validated its applicability. Using the model, an assessment of the impact of the ongoing land reclamation project of about 400 ha in the bay on the fisheries resources was also conducted. The results showed that a substantial mortality of the fisheries resources would take place when hypoxic condition occurs in every summer and the construction of the artificial land will lower the mortality rate of fish during the summer period in the bay. Strong offshore winds cause the upwelling of bottom hypoxic waters in summer and the initial mortality of the fisheries resources increase under northerly offshore wind of 5 m/s or more.

Delignification of disposable wooden chopsticks waste for fermentative hydrogen production by an enriched culture from a hot spring

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 examined and it was found that retention time had no effect on lignin removal or carbohydrate released in enzymatic hydrolysate. The highest percentage of lignin removal (41%) was obtained with 2% NaOH at 100°C, correlated with the highest carbohydrate released (67 mg/g pretreated DWC) in the hydrolysate. An enriched culture from a hot spring was used as inoculum for fermentative H2 production, and its optimum initial pH and temperature were determined to be 7.0 and 50°C, respectively. Furthermore, enzymatic hydrolysate from pretreated DWC was successfully demonstrated as a substrate for fermentative H2 production by the enriched culture. The maximum H2 yield and production rate were achieved at 195 mL H2/g total sugars consumed and 116 mL H2/(L·day), respectively.

Comparison of disinfection effect of pressurized gases of CO2, N2O, and N2 on Escherichia coli

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 pressure (0.3-0.9 MPa), initial concentration, and temperature. The optimum conditions were found to be 0.7 MPa and an exposure time of 25 min. Under identical treatment conditions, a greater than 5.0-log reduction in E. coli was achieved by CO2, while 3.3 log and 2.4 log reductions were observed when N2O and N2 were used, respectively. Observation under scanning electron microscopy and measurement of bacterial cell substances by UV-absorbance revealed greater cell rupture of E. coli following treatment with CO2 than when treatment was conducted using N2O, N2 and untreated water. The physical effects of the pump, acidified characteristics and the release of intracellular substances caused by CO2 were bactericidal mechanism of this process. Overall, the results of this study indicate that CO2 has the disinfection potential without undesired by-product forming.

Decolorization of alcohol distillery wastewater by thermotolerant white-rot fungi.

To determine a thermotolerant fungus strain for decolorization of alcohol distillery wastewater (ADW), 38 fungus strains were studied. Capacity for ligninolytic enzyme production was examined at 35 and 43C on agar media containing 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and MnCl2. At 43°C, four Pycnoporus coccineus strains showed a higher potential for ADW decolorization both on agar media and in liquid media. Immobilized mycelia on polyurethane foam removed about threefold more total phenol than did free mycelia under conditions of shaking at 43°C. Moreover, immobilized mycelia removed nearly 50% more color than did free mycelia.

Compost Stability Assessment Using a Secondary Metabolite: Geosmin

Composting is a process involved not only in transformation of organic matter (OM), but also for transition of the microbial community. Microorganisms can directly provide important information on the stages and characteristics of composting. This paper was aimed at characterizing compost stability by a microbial secondary metabolite, geosmin, which is a volatile compound presenting an earthy smell. Since secondary metabolite production is dependent on the nutrient state of microorganisms, its production in association with physical and chemical parameters was monitored in the laboratory-scale and plant-scale composting processes. The results showed that the peaked geosmin liberation was consistent with stable state of composting indicated by the ambient temperature achieved, a slightly alkaline product and steady states of dissolved organic carbon (DOC), N and P contents and OM degradation in the laboratory-scale experiment. It was also in accordance with the stability identified by the facilities and CO2 respiration rate in the plant-scale composting. In addition, the production of geosmin was correlated with the C/N ratio for the solid sample. These results demonstrated that geosmin levels could be used as an index for the compost stability assessment in different composting processes with various organic solid wastes.

Distributions of Iron, Manganese, Copper and Zinc in Various Composts and Amended Soils

Abstract A detailed observation was conducted on Fe, Mn, Cu and Zn in the composts derived from seafood processing by‐product, garbage, swine manure and sewage sludge, respectively, as well as in amended farmlands. All elements were at lower levels of total contents but a higher percentage of water‐soluble and exchangeable forms in composted seafood processing byproduct and composted garbage than in composted swine manure and composted sewage sludge. Total contents increased in the order: composted seafood processing by‐product ≈ composted garbage < composted swine manure < composted sewage sludge. The applications of composted seafood processing by‐product and composted garbage have neither caused Fe, Mn, Cu and Zn accumulation nor changed their distribution in soils; while the application of composted swine manure has largely increased Cu and Zn contents in soils, mainly in organic matter‐bound form, and that of composted sewage sludge increased Mn, Cu and Zn in soils mainly in carbonate‐bond and Fe‐Mn oxides‐bound ones. Fe is an exception, its total contents in soils decreased with the applications of composts except for composted garbage. Also, the rainfall and irrigation were another two main factors that affected available elements in soils.

The Potential use of Trichoderma Viride Strain FRP3 in Biodegradation of the Herbicide Glyphosate

ABSTRACT A Trichoderma strain was isolated and then identified as Trichoderma viride strain FRP3 based on colony morphology, cell morphology and 18S rRNA analysis. The optimum temperature for growth of T. viride strain FRP3 was found to be 25–27°C. This Trichoderma strain could grow well in a wide range of pH (pH 4–6.5) and the optimum pH was 5 and 5.5. Trichoderma viride strain FRP3 was also evaluated in vitro for potential use in bioremediation of soils contaminated with the herbicide glyphosate, through observation of the growth profiles and the total phosphorus in culture medium containing glyphosate as the sole phosphorus source. The growth profiles of Trichoderma viride strain FRP3 showed considerable growth in culture medium containing glyphosate as the sole phosphorus source. This result was supported by the decrease in the total phosphorus, which indicates a utilization process for glyphosate and perhaps shows that there may be a mechanism for degradation of this compound. This study indicates that the treatment of soil with Trichoderma viride strain FRP3 could be useful in some areas where this herbicide is extensively used.