Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejer.76.7_iii_181

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

The first step in biofuel and/or bio-based bulk chemical material production is assessing the amounts of useful substances in a potential biomass. Sugar, nutrients, ash, and functional ingredients (such as antioxidant compounds) in premature dent corn biomass cultivated as a catch crop (plant density
60 shoots m−2) over different cultivation periods (29 days, 49 days, 83 days) were investigated. The sugar recovery amount was estimated by multiplying two regression curves (saccharification efficiency curve, quadratic regression curve
dry weight growth curve, Gompertz curve). A simple economic analysis for ethanol production from the catch crop biomass was also carried out using previously reported process costs and the estimated sugar recovery amount. High plant density led to accumulation of plant biomass providing high amounts of plant dry weight and derived sugars per unit area. About 2700 g DW m−2 (about 1400 g sugar m−2) was harvested in the 49-day cultivation. The amount is significant compared with biomass yields of other candidates for energy crops. The estimated sugar recovery amount reached its maximum value near the end of experimental period (79-day cultivation). The longer cultivation period was better for sugar recovery although there was a slight decrease in saccharification efficiency with cultivation time. Based on the economic analysis, a higher ethanol price (about 200% higher than the current wholesale price) would be required for catch crop financial independence with around 50-day cultivation. Production of ethanol from catch crop biomass would not be feasible in the current situation. However, condensed biomass production through catch crops is still attractive and requires further research.

DOI： 10.1016/j.indcrop.2017.11.039

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Fermentation of lignocellulosic biomass requires auxiliary materials, including nutrients, to ensure the proliferation of microorganisms. Nutrients are usually inexpensive, but their contribution to the cost is considerable because of the very low prices of fermentation products, such as bio-ethanol. Using substances present in native lignocellulosic biomass as nutrients for fermentation was proposed and demonstrated. Leaves and stalks of corn plants were used as biomass, and nutrients were recovered as a nutrient solution by soaking them in water before alkaline peroxide pretreatment. Pretreated biomass and the nutrient solution derived from the same lot were used for non-sterile simultaneous enzymatic saccharification and thermophilic l-lactic acid fermentation (SSF). Using the nutrient solution in the saccharification step did not impact sugar recovery, and instead improved sugar yields because of the presence of eluted sugars in the solution. The l-lactic acid yield of 0.33 g g(-1) based on native biomass weight indicated that the nutrient solution functioned as a source of nutrients and sugars, especially as a source of essential phosphorus. Comparatively, autoclaved SSF yielded less or no l-lactic acid, indicating an apparent inhibitive effect derived from the nutrient solution on bacterial growth.

DOI： 10.1007/s10163-015-0390-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The cultivation of catch crops has great potential in agricultural areas for the recovery of nutrients, mitigation of groundwater contamination, and secondary utilization of harvestry. To estimate the potential volume of catch crops that can be collected at prospective locations, we simulated the cultivation and collection process at a regional scale using geographic and statistical data. Three types of geographic data, namely the locations of greenhouses, collecting stations and road networks, were used in a geographic information system to compute the volume of collected catch crops and carrying distance between greenhouses and collecting stations. Carbon emission from transportation of the catch crop was calculated using an improved ton-km method, and the results were compared with the carbon content of the catch crop to evaluate the carbon balance. We found that the total fresh weight of the collected catch crops was 67900 t, of which 70% was collected at the top 15 of 73 stations. Carbon emissions from transportation ranged from >1 to 12% of the carbon content of the catch crop. The analytical method used in this study can readily be applied to other environmental studies concerning the collection of agricultural products and other biomass resources.

DOI： 10.1111/tgis.12153

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Nitrous oxide (N2O), which is a greenhouse gas, may be more emitted as an intermediate product of denitrification during biological soil disinfestation. The biological soil disinfestation is a method to suppress soil-borne pathogens under reductive soil conditions produced by the application of organic matter and water irrigation with plastic film. The objective of the study was to determine the effects of different organic matter and mulch films on N2O emissions during biological soil disinfestation. Grey lowland soil amended with cattle compost plus rice bran (0.2%), rice husk (0.2%) or dent corn (0.1%, 0.2% and 0.4%) was incubated at 100% water-holding capacity with or without plastic films made of polyvinyl chloride (PVC) and triple-layer polyolefin (3PO) for 72h at 50 degrees C. Permeation of the two films was also measured at 25 degrees C and 50 degrees C. Results showed that incorporation of organic matter increased N2O emissions compared with no organic matter addition at 50 degrees C. Incorporation of rice bran and dent corn with easily decomposable C and low C:N ratios increased N2O emissions for the first 12h, but thereafter, available C supply from these amendments suppressed N2O emissions. Permeability of mulch films increased at a higher temperature and was larger for PVC than for 3PO. Our study indicated that rice husk should not be used for soil disinfestation and that application rates of organic matter must be determined based on their decomposability. Moreover, mulch film covering would not suppress N2O emission in biological soil disinfestation because of high temperature.

DOI： 10.1080/09593330.2015.1092494

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Language：English   Publisher：Graduate School of Environmental and Life Science, Okayama University  

A short-term study was conducted to investigate the effects of additions of rice husk products on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from paddy soil at different soil moisture contents. Soil amended with raw rice husk (RR, 2% on a dry weight basis), rice husk char (RC, 2%), rice husk ash (RA, 2%) or no amendment (CT) was incubated at 40%, 60%, or 80% water-holding capacity (WHC) in a 100-mL bottle for 120 h. Results showed that N2O emission was lower at 40% WHC compared with other WHC treatments. At 60% and 80% WHC, N2O emissions peaked at 24 h of incubation in most treatments. The highest emission of N2O was recorded in the RR addition at 80% WHC. Additions of RC and RA decreased cumulative N2O emissions from soil at 24 h (by 24% at 60% WHC and 51% at 80% WHC for RC, and 90% at 60% WHC and 80% WHC for RA) compared with the CT treatment. Regardless of the soil moisture content, RR enhanced cumulative CO2 emission for 120 h, whereas no significant difference was detected among RC, RA and CT treatments (P > 0.05). Our short-term results indicated that application of rice husk char or ash to soil reduced N2O emission, whereas direct incorporation of rice husk into soil enhanced CO2 and N2O emissions.

DOI： 10.3107/jesss.7.9

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Authorship：Lead author  

DOI： 10.2208/jscejer.72.III_249

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Denitrification products nitrous oxide ((N2O) and nitrogen (N-2)) were measured in three flooded soils (paddy soil from Vietnam, PV; mangrove soil from Vietnam, MV; paddy soil from Japan, PJ) with different nitrate (NO3-) concentrations. Closed incubation experiments were conducted in 100-mL bottles for 7d at 25 degrees C. Each bottle contained 2g of air-dried soil and 25mL solution with NO3- (concentration 0, 5 or 10mgNL(-1)) with or without acetylene (C2H2). The N2O + N-2 emissions were estimated by the C2H2 inhibition method. Results showed that N2O + N-2 emissions for 7d were positively correlated with those of NO3- removal from solution with C2H2 (R-2=0.9872), indicating that most removed NO3- was transformed to N2O and N-2 by denitrification. In PJ soil, N2O and N-2 emissions were increased significantly (P<0.05) by the addition of greater NO3- concentrations. However, N2O and N-2 emissions from PV and MV soils were increased by the addition of 0 to 5mgNL(-1), but not by 5 to 10mgNL(-1). At 10mgNL(-1), N-2 emissions for 7d were greater in PJ soil (pH 7.0) than in PV (pH 5.8) or MV (pH 4.3) soils, while N2O emissions were higher in PV and MV soils than in PJ soil. In MV soil, N2O was the main product throughout the experiment. In conclusion, NO3- concentration and soil pH affected N2O and N-2 emissions from three flooded soils.

DOI： 10.1080/00380768.2015.1094747

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Fermentation of lignocellulosic biomass requires auxiliary materials such as nutrients for fermentation. Because of the low prices of fermentation products such as bioethanol, the costs of nutrients are not negligible. We have developed the concept of using substances natively present in lignocellulosic biomass as nutrients for the downstream fermentation. The leaves and stalks of young dent corn plants were used as biomass and the nutrients were recovered by soaking them in water before alkaline pretreatment, followed by enzymatic saccharification and fermentation. Performing thermophilic L-lactic acid fermentation using these recovered nutrients support their use as commercially feasible alternatives. A level of recovered nutrients of 40% was sufficient to support the fermentation of recovered sugars derived from the same corn biomass. However, the amount of recovered nutrients required for fermentation was almost double that when using yeast extract based on the amounts of nitrogen and/or phosphorus added. The nitrogen and phosphorus balances in the process indicated that adding nutrients was crucial for promoting fermentation based on the amounts of nitrogen and phosphorus. The nutrients proposed were considered to be effective for fermenting biomass pretreated by alkaline, dilute add, and hydrothermal methods. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.indcrop.2015.02.055

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DOI： 10.2208/jscejer.71.III_323

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IWA PUBLISHING  

A new wastewater treatment process that involves coagulation, ozonation, and microalgae cultivation has been developed. Here, two challenges are discussed. The first was minimizing phosphorus removal during coagulation in order to maximize algal production. The second was to optimize microalgae cultivation; algal species that grow rapidly and produce valuable products are ideal for selection. Haematococcus pluvialis, which produces the carotenoid astaxanthin, was used. Growth rate, nutrient removal ability, and astaxanthin production of H. pluvialis in coagulated wastewater were investigated. After coagulation with chitosan, the turbidity and suspended solids decreased by 89% +/- 8.4 -> 8% and 71 -> 73% +/- 16%, respectively. The nitrogen and phosphorus contents of the supernatant remained at 86% +/- 6% and 69 -> 67% +/- 24%, respectively. These results indicate that coagulation with chitosan can remove turbidity and SS while preserving nutrients. H. pluvialis grew well in the supernatant of coagulated wastewater. The astaxanthin yield from coagulated wastewater in which microalgae were cultured was 3.26 mg/L, and total phosphorus and nitrogen contents decreased by 99.0% +/- 1.4% -> 99% + 1% and 90.3% +/- 7.6% -> 90% +/- 8% (Days 31-35), respectively.

DOI： 10.2166/wst.2015.330

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：DE GRUYTER OPEN LTD  

Catch crop cultivation coupled with subsequent flood activity is an environmental friendly method of removing nutrient salts from soil in greenhouse. However, in comparison with the usual fallow period in greenhouse horticulture in Japan, a longer time is required for cultivation and soil drying after flooding. To minimize such time while retaining catch crop performance, temporal flooding was conducted in an experimental catch crop field of corn before harvest (i.e., pre-harvest temporal flooding), when crops were growing well and most nutrient salts within the soil had been taken up by the roots. Results showed that pre-harvest temporal flooding enhanced crop growth and stomatal opening; hence, evapotranspiration (mostly transpiration) was increased to a high value (3.5 times that of bare soil plot in greenhouse). Therefore, compared with the bare soil field, there was a remarkable pronounced decrease in the soil water content due to evapotranspirational water loss in the catch crop field after temporal flooding. Furthermore, the total nutrient (nitrogen) uptake by crops was also significantly accelerated in relation to pre-harvest flooding owing to the increase in crop growth. It was also found that electrical conductivity and nitrate nitrogen concentration of soil solution (at a soil-water ratio of 1:5) decreased with time owing to root uptake, and were at a fairly low level when pre-harvest flooding was conducted. These results suggest that pre-harvest temporal flooding shortens the implementation time by accelerating soil drying, and increases salt removal by root uptake; thus, this method delivers considerable advantages for practical use in catch crop cultivation.

DOI： 10.2478/s11756-014-0470-9

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCIENCE PRESS  

Dent corn, as a catch crop used for salt removal, was cultivated at different densities, i.e., 7.3 (low density), 59.7 (normal density), and 119.5 plants m(-2) (high density), during a 50 d fallow period after cultivation of a commercial crop in a greenhouse, to analyze the characteristics of nutrient salt (N, K, Mg, and Ca) uptake by roots and to study the effect of plant density on the characteristics associated with crop water use. Leaf area index for the high and normal density treatments reached extremely high values of 24.3 and 14.9, respectively. These values induced higher transpiration rates that were estimated using the Penman-Monteith model with the incorporation of specific parameters for crop and greenhouse conditions. The total N, K, Mg, and Ca contents in the crop canopy at harvest were 26.8, 13.0, 1.0, and 1.7 g m(-2), respectively, under the high density treatment. The dynamics of salt uptake rates for high, normal, and low density treatments were evaluated by assessing weekly changes in salt content, and were subsequently compared against the transpiration rate. A positive linear relationship was obtained between these 2 parameters for: all 3 density treatments and all tested salts. Hence, higher transpiration rates caused higher salt uptake rates through water absorption. On the other hand, salt uptake efficiency per unit water use by cultivation was lower in the low density treatment. Therefore, management procedures with dense planting that induce higher transpiration rates and lower evaporation rate are extremely important for the effective cultivation of corn catch crops.

DOI： 10.1016/S1002-0160(14)60020-5

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

In previous studies, a system consisting of catch crop cultivation and lactate fermentation was proposed in order to reduce greenhouse gas emission and nitrate infiltration from agricultural field. The system also has aims of recovering nutrient and producing lactate from catch crops to gain profitable products. In this research evaluation of the amount of greenhouse gas emission, nitrogen load to water environment and break-even point of introducing the lactate fermentation system of catch crop were conducted. As a result, increased amount of greenhouse gas emission from the whole system is larger than the decreased amount of N₂O gas emission from agricultural field by catch crop. Most of the nitrogen load from agricultural fields cleaned up by catch crop is discharged as waste water from lactate production process. This means non-point source pollution in the agricultural fields is transformed to point source pollution through the system. Evaluation results showed the system could help to reduce the nitrogen load on water environment using advanced wastewater treatment. From the evaluation of the production cost, we found that nutrients extracting system in the previous stage of lactate fermentation is relatively advantageous than other systems. It was found that the break-even point of the system is greater than 105tDryWeight of catch crop, which means it is greater than 18ha of cultivation area of catch crop.

DOI： 10.2208/jscejer.70.III_483

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Overgrowth of aquatic plants, such as water chestnut, has been reported as a regional problem in various areas. We proposed cascade utilization of water chestnut through the recovery of phenolics, phosphorus, and sugars. Phenolics were extracted using 50 g (wet weight) of biomass with 300 mL of acetone, methanol, or hot water, and the yields of total phenolics were 80.2, 56.2, and 49.7 mg g(-1) dry weight of native biomass, respectively. The rate of eluted phosphorus in the phenolic extraction step was 8.6, 14.8, and 45.3 % of that in the native biomass, respectively, indicating that the use of polar organic solvents suppressed phosphorus elution at the phenolic extraction step. Extraction of phosphorus following the phenolic extraction was combined with alkaline pretreatment (1 % NaOH solution) of biomass for saccharification; 64.1 and 51.0 % of phosphorus in the native biomass were extracted using acetone and methanol for the phenolic extraction, respectively. Saccharification following the alkaline pretreatment showed that the glucose recovery rates were significantly increased (p < 0.05) with the phenolic extraction step compared to alkaline pretreatment alone. This finding indicates that extraction of phenolics not only provides another useful material but also facilitates enzymatic saccharification.

DOI： 10.1007/s11356-013-1547-7

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Language：English   Publishing type：Research paper (scientific journal)  

An in situ technology for mitigating diffuse agricultural pollution using catch crops was developed for simultaneously preventing nitrate groundwater pollution, reducing nitrous oxide (N2O) gas emissions, and removing salts from the topsoil. Seasonal changes in the performance of a catch crop were investigated using lysimeters in a full-scale greenhouse experiment with 50 d cultivation of dent corn. Catch crop cultivation significantly reduced the leached mineral nitrogen by 89-91% in summer, 87-89% in spring, and 61-82% in winter, and it also significantly reduced the N2O emission by 68-84% in summer. The amounts of nitrogen uptake by the catch crop were remarkably higher than those of leached nitrogen and N2O emission in each season. Catch crop cultivation is a promising technology for mitigating diffuse agricultural pollution. © IWA Publishing 2013.

DOI： 10.2166/wst.2013.258

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Catch crop candidates (corn, guinea grass) for recovering nutrients from farm soil and aquatic plants (water caltrop, water hyacinth) were utilized to produce L-lactic acid. The efficiencies of pre-treatment methods for enzymatic saccharification and L-lactate production of two fermentation processes, thermophilic simultaneous saccharification and fermentation (SSF), as well as separate saccharification and fermentation, were compared. Conditions were set at 55 degrees C and pH 5.5 for non-sterile fermentation. Alkaline/peroxide pre-treatment proved the most effective for saccharification in pre-treated corn, guinea grass, water caltrop and water hyacinth with glucose yields of 0.23, 0.20, 0.11 and 0.14 g/g-dry native biomass (24-hour incubation period), respectively. Examination of the two types of thermophilic L-lactate fermentation employed following alkaline/peroxide pre-treatment and saccharification demonstrated that the L-lactate yield obtained using SSF (0.15 g/g in the case of corn) was lower than that obtained using separate saccharification and fermentation (0.28 g/g in the case of corn). The lower yield obtained from SSF is likely to have resulted from the saccharification conditions used in the present study, as the possibility of cellulase deactivation during SSF by thermophilic L-lactate producing bacteria existed. A cellulase that retains high activity levels under non-sterile conditions and a L-lactate producer without cellulose hydrolysis activity would be required in order for SSF to serve as an effective method of L-lactate production.

DOI： 10.1080/09593330.2012.669412

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Greenhouses are usually irrigated after cropping to remove accumulated salts in the topsoil. Nitrate remained in the soil is reported to be transported to groundwater due to the irrigation, resulting in high nitrate concentration in ground or surface waters. The present study evaluated the effect of a catch crop (dent corn) on leaching losses of nitrogen and phosphorus during a fallow period (catch crop cultivation, salt removal irrigation and reductive soil disinfection) in a farmer's eggplant greenhouse in Okayama, Japan, in 2010 and 2011. Nitrogen leaching was greatly reduced owing to the nitrogen uptake by the catch crop with compared to the control (p < 0.01). Differences of nitrogen losses during the fallow period between treatments were 12.2 g m^-2 in 2010 and 5.4 g m^-2 in 2011, probably due to different contents of mineral nitrogen remained in the soil after eggplant harvests. On the other hand, phosphorus leaching was not significantly different between treatments (p > 0.05). The effect of phosphorus uptake by the catch crop may be masked because of the large amount of mineral phosphorus accumulated in the soil. Our results clearly showed that catch crop growth during a fallow period reduced nitrogen leaching in the eggplant greenhouse.

DOI： 10.2208/jscejer.68.III_103

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Authorship：Lead author,　Corresponding author   Language：English   Publisher：IWA PUBLISHING  

As a result of long-term continuous use of fertilizers in farm land, a large amount of nutrients accumulate in the soil, increasing the risk of eutrophication or nitrate pollution of groundwater. For rehabilitating the farm soil and recovering nutrients such as nitrogen, phosphorus and potassium, a new system has been developed by our research group. This paper discusses the methodology of extracting nutrients from biomass in order to recover phosphorus and other nutrients in crystal form. Around 80% or higher extraction rates were achieved for phosphorus and potassium by soaking the powdered tissue in distilled water or 1% NaOH solution for 24 h. The extracted phosphorus and potassium act as a potential resource for recycled fertilizer or other industrial materials.

DOI： 10.2166/wst.2012.291

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The behavior of inorganic elements (including phosphorus, nitrogen, and metals) during sludge zonation was investigated using batch tests and the effects of metals on sludge solubilization were elucidated. A decrease of similar to 50% in the ratio of sludge solubilization was found to relate to a high iron content 80-120 mgFe/gSS than that of 4.7-7.4 mgFe/gSS. During sludge zonation, the pH decreased from 7 to 5, which resulted in the dissolution of chemically precipitated metals and phosphorus. Based on experimental results and thermodynamic calculation, phosphate precipitated by iron and aluminum was more difficult to release while that by calcium released with decrease in pH. The release of barium, manganese, and chrome did not exceed 10% and was much lower than COD solubilization; however, that of nickel, copper, and zinc was similar to COD solubilization. The ratio of nitrogen solubilization was 1.2 times higher than that of COD solubilization (R(2) = 0.85). Of the total nitrogen solubilized, 80% was organic nitrogen. Because of their high accumulation potential and negative effect on sludge solubilization, high levels of iron and aluminum in both sewage and sludge should be considered carefully for the application of the advanced sewage treatment process with sludge zonation and phosphorus crystallization. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.watres.2010.12.011

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Language：English   Publishing type：Research paper (scientific journal)  

We cultivated dent corn as a catch crop for controlling soil salt conditions in field plots at different densities, namely, 7.3 (low), 59.7 (normal) and 119.5 (high) plants m -2 in a greenhouse, where environmental elements and plant growth were measured for analyses of evapotranspiration components relating to the catch crop effects. Using the Penman-Monteith model with specific parameters incorporated for the crop and greenhouse, leaf transpiration and soil evaporation were estimated. Further crop coefficients were analyzed by dividing actual evapotranspiration by a reference evapotranspiration determined from meteorological data. Leaf area index for the normal and high density treatments reached 14 and 22, respectively, which were extremely high values compared to those for various other crops. Transpiration and its ratio to evapotranspiration increased with plant growth and density. Crop coefficients also increased with leaf area index and transpiration, and the coefficients for the normal and high density treatments reached high values of 1.5-2 and 2-3, respectively. These findings reveal characteristic features of plant growth and water dynamics in a catch crop field. The results of this study will contribute to the optimization of catch crop cultivation and to elucidate the crop's effects on soil salt conditions in greenhouses.

DOI： 10.2525/ecb.49.217

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Language：Japanese   Publisher：Japan Society on Water Environment  

To understand the phenomena occurring in Lake Biwa and predict the effects of measures for improving water quality, constructing a simulation model that can calculate the hydrological and material cycle and reaction process in the basin with high accuracy is the most effective way. In this study, a Lake Biwa Basin simulation model with the integration of three components of land, lake flow, and lake ecosystem is constructed and named "Lake Biwa Basin Hydrological and Material Cycle Simulation Model". Distributed and 3-dimensional models are adopted; these models can simulate water quality and quantity unsteadily by considering weather, social conditions, and so on. As a result, river discharge and quality in main rivers, such as Yasu River and Hino River, and water temperature, average quality and seasonal variation in the lake are adequately calculated. On the other hand, it is insufficient to calculate water quality of the time series and distribution in Southern Lake; thus, it is a future challenge to evaluate spatial-temporal lake water quality precisely.

DOI： 10.2965/jswe.34.125

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Language：English   Publisher：Japan Society on Water Environment  

Mires are loosing their natural state as a result of human activities. Recently natural Sphagnum mires in Hokkaido, Japan, have been disappearing as a result of the proliferation of alders. Here we show that such proliferation is caused by the inflow of phosphorous compounds as non-point pollutants. Those phosphorous compounds flow in from agricultural fields around mires. The constituents of groundwater or surface water make alders proliferate rapidly. Phosphorous, a typical non-point-polluting nutrient, contributes to the growth of alders, which assimilate atmospheric nitrogen.

DOI： 10.2965/jwet.2009.103

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DOI： 10.2166/WPT.2009.021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

The applicability of sludge ozonation on wastewater treatment processes was investigated to reduce the amount of excess sludge without losing phosphorus removal efficiency. Solubilization degree per ozone consumption for general sludge was in the range from 2.4 to 5.8 gSS/O-3 and from 4.1 to 7.7 gCOD/gO(3). Around 80 to 90% of solubilized organics was biodegradable at a solubilization degree of 0.3. Based on the experimental results, a lab-scale plant with sludge ozonation and phosphorus crystallization was constructed to investigate the treatment performance. Amount of excess sludge was reduced by 93% with almost complete removal of soluble BOD and phosphorus removal efficiency of more than 80%. The percentage of the effluent CODCr discharge increased from 10% to 14-17% after installing ozonation and crystallization because of the formation of non-biodegradable organic substances in ozonation process. Energy consumption of the innovative advanced process is comparable or can be even smaller than that of the conventional anaerobic/oxic (A/O) process in spite of the installation of ozonation and crystallization.

DOI： 10.1080/01919510701861292

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

A new advanced treatment system, which consists of biological nutrient removal process combined with reduction of excess sludge by ozonation and phosphorus recovery by crystallization and polishing-up ozonation process, was developed based on the fundamental studies and demonstrated by the demonstration plant set in AICHI EXPO 2005. Reduction of withdrawn excess sludge by 90% and phosphorus recovery by 70% were accomplished without any adverse effects on biological nutrient removal. The concentrations of SS, BOD, T-P and T-N in the effluent were less than 1.0, 3.0, 0.5 and 10 mg/L, respectively. EDCs were reduced to almost undetectable level and 2-log disinfection of Bacillus subtilis was established. The energy amount required for the operation was saved by 40% when compared with a conventional system to get the same level of water quality.

DOI： 10.1080/01919510802070710

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Language：Japanese   Publisher：Japan Society on Water Environment  

The concentrations of PCBs in sea water and blue mussels ranged from 0.5 to 4.0 ng · l^-1 (mean ± S.D.: 1.8 ± 0.6 ng · l^-1) and from 3.1 to 69.8 ng · g^-1 -wet (24.0 ± 19.0 ng · g^-1-wet), respectively, in the Seto Inland Sea. The main homologues of PCB in seawater and blue mussels were T₄CBs and H₆CBs, respectively, and their content ratios to total PCB were 40∼50%. Homologues with high chlorine content accumulated in blue mussels. By principal component analyses associated with the homologues of PCB in seawater, blue mussels and sediment, it was clearly shown that the sea area in Osaka Bay and Harima-nada were mainly contaminated with low-chlorine-content homologues of PCB which were mainly used in condenser and heating fluid, and that the other sea area was mainly contaminated with high-chlorine-content homologues which were mainly used in paints and varnish. More detailed analyses were possible by the principal component analyses with selected and important isomer data.

DOI： 10.2965/jswe.30.457

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DOI： 10.2208/jscejg.63.149

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Language：Japanese   Publisher：日本陸水学会  

DOI： 10.14903/jslim.72.0.36.0

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

DOI： 10.11520/jshwr.20.0.90.0

CiNii Article

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2208/jscejg.63.179

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Language：Japanese   Publisher：The Society of Instrument and Control Engineers  

DOI： 10.11499/sicejl1962.45.851

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Other Link： https://jlc.jst.go.jp/DN/JALC/00286432670?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：I W A PUBLISHING  

This paper shows the potential application of a new sewage treatment process with technologies of excess sludge reduction and phosphorus recovery. The process incorporated ozonation for excess sludge reduction and crystallisation process for phosphorus recovery to a conventional anaerobic/oxic (A/O) phosphorus removal process. A lab-scale continuous operation experiment was conducted with the ratio of sludge flow rate to ozonation tank of 1.1% of sewage inflow under 30 to 40 mgO(3)/gSS of ozone consumption and with sludge wasting ratio of 0.34% (one-fifth of a conventional NO process). Throughout the operational experiment, a 60% reduction of excess sludge production was achieved in the new process. A biomass concentration of 2,300 mg/L was maintained, and the accumulation of inactive biomass was not observed. The new process was estimated to give a phosphorus recovery degree of more than 70% as an advantage of excess sludge reduction. The slight increase in effluent COD was observed, but the process performance was maintained at a satisfactory level. These facts demonstrate an effectiveness of the new process for excess sludge reduction as well as for phosphorus recovery.

DOI： 10.2166/wst.2006.424

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

An advanced sewage treatment process has been developed, in which excess sludge reduction by ozonation and phosphorus recovery by crystallization process are incorporated to a conventional anaerobic/oxic (A/O) phosphorus removal process. The mathematical model was developed to describe the mass balance principal at a steady state of this process. Sludge ozonation experiments were carried out to investigate solubilization characteristics of sludge and change in microbial activity by using sludge cultured with feed of synthetic sewage under A/O process. Phosphorus was solubilized by ozonation as well as organics, and acid-hydrolyzable phosphorus (AHP) was the most part of solubilized phosphorus for phosphorus accumulating organisms (PAOs) containing sludge. At solubilization of 30%, around 70% of sludge was inactivated by ozonation. The results based on these studies indicated that the proposed process configuration has potential to reduce the excess sludge production as well as to recover phosphorus in usable forms. The system performance results show that this system is practical, in which 30% of solubilization degree was achieved by ozonation. In this study, 30% of solubilization was achieved at 30 mg O-3/gSS of ozone consumption. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.watres.2004.11.035

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Language：Japanese   Publisher：日本下水道協会  

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DOI： 10.11532/proes1992.40.501

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Effects of nitrification on BOD were evaluated with two kinds of batch experiments, and the problems caused by N-BOD were discussed with descriptions of test manuals, experimental data and literature review. The main results drawn in this study are as follows:(1) most of water analysis manuals do not clearly describe nitrification on BOD test is an interference nor the matter to be measured, (2) ammonium nitrogen in dilution water causes a positive error in BOD test, and can overestimate N-BOD values more than two times, (3) BOD values measured with present methods can not express the pollution level because of N-BOD appearance during the purification development. As a conclusion, it is recommended that oxygen consumption by nitrification should be eliminated from the contents of BOD, and the test procedure should adapt an inhibition process for nitrification in BOD measurement.

DOI： 10.11532/proes1992.40.531

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Language：Japanese   Publisher：Japan Society on Water Environment  

The mass change of nitrogen in Lake Biwa was shown, and its cycle was discussed and compared with the input/output loading. Nitrogen exists at 10.5X103 ton in average, and its minimum and maximum mass are 7.6X103 ton, 13.4X103 ton, respectively. Its average mass is equivalent to 133% of the annual input loading, resulting in 1.6 months of residence time, which is shorter than 5.5 years of hydraulic retention time. This indicates that nitrogen in the lake is removed by settling onto the lake bottom or denitrification, and the removed mass is estimated to be 71% of the input loading. Phytoplanktons mainly utilize ammonium nitrogen in epilimnion whose mass is only 1% of the total mass in the lake. rather than other inorganic nitrogen amounting to more than ten-fold of ammonium nitrogen. During the stratification period, almost all decomposed nitrogen in the organic matter is oxidized into nitrate, and half of them is likely to be removed by denitrification.

DOI： 10.2965/jswe.26.663

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Other Link： https://jlc.jst.go.jp/DN/JALC/00232494929?from=CiNii

Language：Japanese   Publisher：Japan Society on Water Environment  

The estimation of material mass in bodies of water such as lakes provides much information on water quality formation mechanism since it enables evaluation of mass balance in the body of water examined. However, such estimation is difficult, because water quality is not uniform and a precise water quality survey is actually difficult in a large lake. In this paper, mass estimation methods are proposed and compared with each other. In each method, material mass in Lake Biwa, Japan was estimated based on water quality data at 75 points in the lake. The spline technique that interpolates the concentration value in 500X500X1m-size mesh in the lake with a σ value of 0.3 was selected as the most suitable estimation method. Judging from the N/P ratio, mass values estimated by this technique were more reliable than those reported previously. Nitrogen and phosphorus are present in Lake Biwa at 7.6-13X10³ tonN and 190-340 tonP, respectively, and their averages in 20 surveys from 1995 until 2000 were 11X10³ tonN and 230 tonP, respectively.

DOI： 10.2965/jswe.25.599

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Other Link： https://jlc.jst.go.jp/DN/JALC/00159919109?from=CiNii

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：I W A PUBLISHING  

Forest river surveys were carried out at upper streams of several rivers in the Lake Biwa watershed to understand the water quality characteristics of the rivers, and to find out their relationships with forest features such as geographical. geological and vegetational data. The results showed: (1) Forests have some purification functions for nitrogen and organic matter. but become sources for most of ionic species. (2) Main mineral species in forest rivers are Ca2+, Mg2+ and Na+, HCO3-, CO32-, Cl-, SO42- and SiO2. (3) Loading from forests was 0.4-7 kg/km(2)/d for TN and 0.01-0.3 kg/km(2)/d for TP. (4) River quality reflects the properties of each forest, and is unique to the place, especially in ionic species such as Ca2+ and Cl-. (5) A cluster analysis successfully categorized ionic components into several groups.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I W A PUBLISHING  

To understand the eutrophication phenomena in Lake Biwa, Japan, a research project for the water quality formation processes was executed. This paper presents phosphorus mass changes in water body in Lake Biwa from April 1995 to January 2000 and discusses the main factors of the change, Phosphorus mass ranged from 190 to 350 t, with an average of 260 t. DP mass in 1995, '97 and '98 showed seasonal change patterns, while non-periodical phenomena seemed to control the PP mass. Phosphorus mass was increased about 15 t in epilimnion from April to July while nitrogen showed a 50 t decrease. This disagreement suggests that some processes selectively accumulated phosphorus in epilimnion during this period. However, such an increase in phosphorus was not observed in 1996 and '99. Air temperature was lower and much snowfall was recorded in 1996 and '99, suggesting that coldness in winter season weakened the phosphorus accumulation process to depress the mass in epilimnion in summertime. Water temperature increase seemed to be delayed in proportion to total snowfall, but thermocline was formed independently of coldness. Hence, the idea was abandoned that the delay of thermocline formation encouraged the sedimentation process, and biological activities were considered to be the main factor controlling phosphorus mass in the epilimnion in Lake Biwa.

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Publisher：Japan Society of Civil Engineers  

Aquatic macrophytes form a "system" consisting of the macrophytes themselves and periphytons attached to them. The system has a significant role in purifying water. In this study, we evaluated such water purification functions of macrophytes-periphytons "system", as removing nutrients of the river water prior the river flowing into a lake. Using the data obtained by a field survey and laboratory tests, we made a model of the water quality purification by macrophytes and the periphytons. As a result, we found (1) the "system" of aquatic macrophytes and periphytons play a role as "catalysis" to suspend the dissolved nutrients, and (2) a physical purification function by the aquatic macrophytes which act as a filter to remove suspended solid from the water. Also, we clarified the efficiency of these functions at the water surface.

DOI： 10.11532/proes1992.33.349

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Language：Japanese   Publisher：京都大学環境衛生工学研究会  

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