ENVIRONMENTAL ENGINEERING RESEARCH
Online ISSN : 1884-829X
Print ISSN : 1341-5115
ISSN-L : 1341-5115
Current issue
Showing 1-50 articles out of 75 articles from the selected issue
  • Naoki TAKAHASHI, Yoshio SATO, Yoshinobu ISHIBASHI, Youn-Hee Han, M. T. ...
    2008 Volume 45 Pages 1-8
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    The influences of various chemicals causing anaerobic arsenic leaching from sediment towards groundwater in the alluvial aquifers in Bangladesh were investigated. Consequently, significant influence on arsenic leaching was observed by using phosphoric acid as a leaching agent. Leaching was further promoted when organic phosphate particularly triphenylphosphine, concentration 630 times against control, was utilized. Conversely, remarkable arsenic leaching was also noticed in an alkaline condition by using ammonia. Besides, functions of microorganisms were also examined. Finally, estimation of sorption reaction coefficients was performed to be used with the fundamental equations illustrating arsenic transport in the reducing aquifers.
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  • Hyungjun LEE, Takanori MASUDA, Yoshihiko HOSOI
    2008 Volume 45 Pages 9-17
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    The purpose of this study is to characterize and quantify the SS (Suspended Solids), PN (Particulate Nitrogen) and PP (Particulate Phosphorus) discharged from agricultural area which located in Lake Koyama watershed of Tottori city. According to the survey carried out on fine days, there is much difference of pollutants discharge among the agricultural events. SS, PN and PP concentration showed a sharp peak in puddling and rice-planting periods. SS and PP concentration increased in the first half of mid-summer drainage period. PN showed a peak in harvest period. About the pollutants net loading, many pollutants of SS, T-P and PP are discharged in puddling and rice-planting periods, while flow rate is small. On the other hand, T-N and PN loading sometimes showed negative net loading. Rainy season loading was estimated by tank model and L-Q equation. From the fine day and rainy season results, unit loadings of SS, T-N, PN, T-P and PP were estimated at 785, 16.9, 3.9, 6.7, 3.3 kg/ha/yr.
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  • Yuji OKAYASU, Yutaka SUZUKI
    2008 Volume 45 Pages 19-28
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    In order to understand runoff-mechanisms of nutrient pollutant from watershed to receiving water body, concentrations of tracers (i. e., sodium ion, potassium ion) and nutrients in domestic wastewater and occurrence of their runoff in dry weather were studied in two watersheds. In a watershed, where mainly domestic wastewater is discharged, results show that domestic wastewater is diluted by base flow. In the other watershed, where considerable amount of livestock wastewater is suspected to be released, it was possible to estimate existence of point source except for domestic wastewater by analyzing ratio between tracers and ratios of nutrient to the tracer.
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  • Seiya HANAMOTO, Hiroki SUGISHITA, Naoyuki YAMASHITA, Hiroaki TANAKA, I ...
    2008 Volume 45 Pages 29-37
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Degradation of PPCPs in the water environment was evaluated. On the assumption that the degradation is a first-order reaction, the reaction constants were calculated by comparing the mass load of upstream and downstream and the time of flow at Yodo River System. Batch experiments were also conducted and the reaction constants were determined and compared with those of the river surveys. These were greatly different for ketoprofen, azithromycin, diclofenac and levofloxacin, suggesting the other mechanisms of decrease in the concentrations such as photodegradation or adsorption to the sediments. In the river surveys, biodegradability was found much different depend on the sites.
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  • Takayuki NAGAYA, Yoshiki SHIRAISHI, Asuka UKESE, Kouki ONITSUKA, Makot ...
    2008 Volume 45 Pages 39-50
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Before river improvement work, it is necessary to conduct the environmental assessment. However, the accuracy of the environmental assessment is not so high, because the preference curves of the flow depth, velocity and so on have been not clear. Recently, the preference curves of the flow depth, velocity and substrate concerning with Zacco platypus, Zacco temminckii, Tribolodon hakonensis and Rhinogobius flumineus are suggested by Komura. In this study, the living environment of those fishes in Gokasegawa River is predicted on the basis of preference curves suggested by Komura. Further, environmental characteristics were compared. As a result, the most suitable cross section was suggested.
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  • Jun-ichi SAKAMOTO, Haruhiko MATSUMOTO, Kesayoshi HADANO, Takuzo AMANO
    2008 Volume 45 Pages 51-58
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    The formation of oxygen-poor water and the occurrence of hydrogen sulfide in estuary are caused by the sludge which contains a lot of organic substance. In order to examine measures against the water environment problems caused by the sludge, it is necessary to evaluate bottom shrear stress which considered to exert influence on the behavior of bottom material. In our study, the characteristics of time variation of salinity flux and ss flux calculated from results of field observation were considered. The bottom shear stress was evaluated by using the change of water level obtained by one-dimensional unsteady flow analysis and the density distribution obtained by field observation. As a result, it is expected that the bottom shear stress is governed by the slope of water surface and the horizontal density gradient when the tip of saline wedge passes.
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  • Shinichi WATAYA, Yoichi NAKANO, Tsuyoshi IMAI, Satoshi NAKAI, Wataru N ...
    2008 Volume 45 Pages 59-64
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    The Ohtagawa flood way is connected with Ohtagawa river via Gion floodgate. Under the normal times, the discharge water volume for the Ohtagawa flood way is maintained to keep its structure and functions, such as biological productions, however flushing is carried out in the case of a heavy rain which may cause flooding of Ohtagawa river. The flushing inevitably disturbs the tidal flat ecosystem developed in the flood way. This research was carried out to investigate how the flushing disturbs the estuarine tidal flat ecosystem developed in the mouth of Ohta flood way. The flushing caused runoff of the tidal flat surface soil and/or macrobenthos, of which degrees were dependent on the water volume and the period of flushing. The measurement of the tidal flat surface level revealed that about 10 cm of the surface soil was run off by the flushing in 2006 with 5.57m of water level measured at Yaguchi-daiichi observing station, while that with 8.81 m in 2005 vanished 50% of the macrobenthic population. After the flushing, the level of the tidal flat surface and macrobenthic population were finally recovered to the original conditions.
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  • Yukiko KAWAMUKAI, Naoya SATTA, Takahiro TATEISHI
    2008 Volume 45 Pages 65-71
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    In this research, the growth inhibition of Branica campestris induced by bromic was examined to estimate effect of counter cation that is potassium (K) and sodium (Na). Consequently, KBr didn't decrease length and dry weight of the edible part and just promoted growth increasingly. Growth inhibition of bromate was getting stronger with its concentration. At low concentration of 1 mg/L KBrO3, Brassica campestris grew larger than the control on account of promotion effect of K. NaBrO3 caused impediment for growth at the same concentration. As good correlation was showed between growth inhibition induced by KBrO3 and bromate concentration, a linear regression equation was obtained. On the other hand, growth inhibition induced by NaBrO3 was fitted well for logarithmic equation.
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  • Kazuya NISHIDA, Yumiko FURUSAWA, Daisuke OKAZAKI, Yoshiteru KIMIZUKA
    2008 Volume 45 Pages 73-80
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    This study clarifies the fanction of the fish habitat and temporal change in fish fauna and environmental factors in a wand-channel and wand-pool which were constracted in the river of an urban area. The investigation was carried out from 1996 to 2008 in the lower reach of the Edo-River, its wand-channel and wand-pool.
    As a result, Pseudorasbora parva, Oryzias latipes latipes and Gambusia affinis which were small and resident fish, inhabited in wand-channel and wand-pool. It was suggested that Cyprinus carpio and Carassius spp. spawned and the juvenile grew in there. Otherwise, the fanction deteriorated because of shallowing of water depth. However, it was suggested that the fanction restored by re-excavation. It was thought that demonstrating the factor that influence on inhabiting and spawning of the fish in wandchannel and wand-pool was hereafter issue.
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  • Yusuke IKEGAMI, Munehiro NOMURA, Yumi NAGAHAMA, Kazunori NAKANO, Osamu ...
    2008 Volume 45 Pages 81-87
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    It is well known that a seagrass (Zostera japonica) has a function to let the benthic fauna of intertidalzone increase. To conserve and construct seagrass bed, it is important to clarify the relationship between growth conditions and environmental factors. However, it is difficult to understand the factors that affectthe growth of Z japonica from the results of a field survey. Therefore, a laboratory experiment wascarried out to study the effect of environmental conditions such as emergence time and bottom sedimentconditions on the growth of Z japonica. The growth of Z japonica was found to be good in thesubmergence condition, but it was not affected by the various sediment conditions. Thus, it was indicatedthat compared to sediment, emergence time is one of the most important environmental factors on thegrowth of Z japonica.
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  • Yumi NAGAHAMA, Masateru OSHIMA, Shuro YOSHIKAWA, Kenji NEMOTO, Osamu N ...
    2008 Volume 45 Pages 89-95
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    We investigated the influence of coastal erosion on macrobenthos and demersal fishes in Miho coast, Japan. The coastal erosion in this area has been observed since 1983. In this study, it was shown that strong sediment flow on the sea floorwas formed with long-term coastal erosion. Furhermore, it was suggested the generation of consecutive sediment flow brought movement of bottom of the sea soil in 25m water depth where the change of geographical features was not observed, and the specific demersal environment was difficult to form particulate organic matters. It is not only few food of macrobenthos that available, but also the fragile of habitats at the sea bottom, a place of primary succession, was occured. As a result, macrobenthic fauna was poorly build-up. In addition to, it was suggested that The richness of demersal fishes as macrobenthic feeder was decreased due to the decay of food resource that influences the initial growth and the reproduction of demersal fishes.
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  • Junko HAGIHARA, Masahiko SEKINE, Akihiko FUJII, Sayumi OZOE, Moriyoshi ...
    2008 Volume 45 Pages 97-102
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    The purpose of this research is to develop a bivalve predation detecting procedure. Clam predators like eagle ray (Aetobatus flagellum) crash clam shell to eat it. Firstly, we reveal the fact that eagle ray creates shot sounds when it eats short-necked clams through a sea water tank experiment. Secondly we make computer programs to count the pulse number included in a shot. The sounds created by the ray tend to include several pulses in a shot, whereas the sounds created by the crab tend to include only one or two pulses. A shot including more than threepulses can be the proof of the predation of the ray with 48% accuracy. This technique can be utilized for a ray migration monitoring system and/or a trigger device for a predation prevention system such as electric shocker.
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  • Shuhei MASUDA, Munehiro NOMURA, Fumiyoshi TSUBONE, Nobuo CHIBA, Naoshi ...
    2008 Volume 45 Pages 103-112
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Both of the field and the literature survey have been carried out to investigatethe mechanism of the water-bloom production in Urushizawa dam reservoir. From the literature examination, the average value of the tempreture of the surface water was 22.3°C in the year in which the water-bloom was generated, 17.4°C in the year in which that was not. The cyanobacteria occupied larger than the greenalgae and the diatom when the tempreture of the surface water, TN, TP and TN/TP ratio was relatively high. This tendency was same in both of the field and the literature survey. It was indicated that the production of the cyanobacteria was derived by the vanish of PO4-P in the surface water. It was suggested that the vanish of PO4-P in the surface water was derived by the production of diatoms in spring, the discharge of diatoms to the outside of resouvoir and sedimentation. The increase of inflow due to the flash of the river promoted the production of the green algae, because of the disturbance of the aquatic environments in the dam reservoir and the supply of the phosphrus.
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  • Yuji SAKUNO, Tsuneo MATSUNAGA
    2008 Volume 45 Pages 113-119
    Published: November 28, 2008
    Released: June 27, 2011
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    The objective of this study is to evaluate the estimation accuracy of high chlorophyll-a concentaration (Chl.a) in the brackish lake (The test site is Lake Shinji) using the spectral reflectance data. As a result, the Chl.a estimation accuracy of “Lake Shinji Model” proposed by authors in the past was estimated to be 5.9μg/l (RMSE). When the high Chl.a estimation model proposed in the world was applied to Lake Shinji, the correlation of the reflectance ratio of “700 nm and 675 nm” and “705 nm and 675 nm” and Chl.a was high (RMSE: about 6ug/l). In addition, if the reflectance ratio of 530 nm and 670 nm is used in satellite GCOM/SGLI sensor in the future, the Chl.a in the lake is estimated by 7.2μg/l error (linear model).
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  • Tsuyoshi IMAI, Tomoyuki MURAKAMI, Takaya HIGUCHI, Masahiko SEKINE
    2008 Volume 45 Pages 121-129
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    In this study, a method of using high-dissolved-oxygen water to purify bottom sediment in closed body water was confirmed to be effective. In addition, the prevention of phosphorus release from the bottom sediment using high-dissolved-oxygen water was also conducted. A pilot-scale oxygen dissolver was set up at the damreservoirs in Yamaguchi, Japan and an on-site study was performed at two water quality (the first stages of thermocline formation and the thermocline formation after a month). The results indicated that when starting with the first stages of thermocline formation, it was possible to spread the high dissolved oxygen water across the bottom layer without any diffusion in the upper direction. Furthermore, the existence of high dissolved oxygen water could prevent the release of phosphorus from the bottom sediment. On the other hand, after a month from the thermocline formation, the decrease of the diffusion distance by the production of the brown floc in the pilot-scale oxygen dissolver was detected. Therefore, itis better to introduce the high-dissolved-oxygen water from the first stages ofthermocline formation than the thermocline formation after a month. This study revealed the effectiveness of high dissolved oxygen water for the improvement in the water quality of closed body water.
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  • Ken USHIJIMA, Kuniyoshi SHIMA, Kohji YAMAZAKI, Toshiaki SHIBATA, Mitsu ...
    2008 Volume 45 Pages 131-137
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Microcystis sp. can overwinter on sediment, and it is suspected as one of major source of blooming on next summer. However, the mechanism of recruitment from sediment to water column remains unknown yet. This study tried to find predominant factor (s) of recruitment, excluding physical factors such as resuspension by flow. We observed recruitment in vitro under various condition, which may affect recruitment in actual dam lake. The results showed that; 1.recruitment is observed regardless of dark or light, 2. recruitment is observed regardless of low or high dissolved oxygen, 3. water temperature rise was supposed as one of predominant triggers for recruitment, and threshold temperature proberbly exist between 10 to 15° C.
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  • Yohei SATO, Ayumi ITO, Noriaki TATE, Atsushi SASAKI, Jiro AIZAWA, Teru ...
    2008 Volume 45 Pages 139-145
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    The impact of coexistent metal cations on the survival of diatom in the presence of polynuclear hydroxyl-aluminium ion was studied through the cultivation of Nitzschia palea under a weakly acidic condition (pH=6) and the monitoring of chlorophyll a. The presence of Zn higher than 0.2mg/l inhibited the survival of Nitzschia palea without Al. The presence of polynuclear hydroxyl-aluminium ion higher than 0.4mg/l inhibited the survival of Nitzschia palea without Zn. However, the survival of Nitzschia palea was adversely affected by the coexistence with lower level of Zn (0.03mg/l), even though the concentration of polynuclear hydroxyl-aluminium ion was 0.1mg/l. These results indicated that the coexistence of low levels of polynuclear hydroxyl-aluminium and Zn would cause the complex ecological effect on aquatic attached diatom. On the other hand, the coexistence with Ca or Mg higher than 10mg/l attenuated the adverse effect of polynuclear hydroxyl-aluminium ion on the survival of Nitzschia palea. However, the effect of Ca or Mg would be insignificant because their concentrations are lower than 10mg/l in water environment such as rivers.
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  • Shiori SASAKI, Manabu FUJII, Hiroaki ITO, Yoshifumi MASAGO, T. David W ...
    2008 Volume 45 Pages 147-155
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Iron is one of the most important micronutrients for the growth of M.aeruginosa, one of the cyanobacteria forming toxic blooms in closed freshwater systems of the world. Recent studies have shown that the extracellular reduction of ferric iron mediated by superoxide is a key step in the process of iron acquisition by some marine phytoplankton. However, little is known about the iron uptake associated with superoxide generation. We investigated the effect of extracellular superoxide generation on the growth and iron uptake of M. aeruginosa. Our results suggested that superoxide generation associated with cell surface and ferrous iron form can participate in iron uptake.
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  • Mariko SHIOIRI, Fumihiko TAKEDA, Nobuo CHIBA, Munehiro NOMURA, Kazunor ...
    2008 Volume 45 Pages 157-162
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    It was confirmed that allelopathic effect is influenced by nutrient condition. But existing method of algal bioassay system can't exclude the influence of nutrient, because nutrient is added not to be a limiting factor. In this research, we established a new bioassay method that test algae Microcystis aeruginosa could growth without any nutrient, and examined the nutrient influence to the polyphenol's allelopathic effect by the new method. Furthermore the allelopathic mechanism was studied by applying DCMU (3-(3, 4-dichlorophenyl)-1, 1-dimethylurea) and glucose. As a results, pyrogallic acid (PA) had a allelopathic effect to attack algae cell directly, and the allelopathic effect was enhanced when nutrient exists. It was also revealed that PA inhibits M.aeruginosa from photosynthesizing.
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  • Fumihiko TAKEDA, Mariko SHIOIRI, Munehiro NOMURA, Kazunori NAKANO, Osa ...
    2008 Volume 45 Pages 163-168
    Published: November 28, 2008
    Released: June 27, 2011
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    Novel bioassay method that test micioalgae can show the maximum specific growth rate μmax regardless of nutrient conditions in test at was constructed. The method and a previous bioassay method was compared based on the evaluation of growthinhibiting effect by the extracts and culture solution of a brown alga Sargassum homeri using diatom Skeletonema costatum. As a result, the growth-inhibiting effect of the odract in a pevious bioassay method was underestimated compared to that in the novel bioassay method, which would be because of the long-term bioassay period and the de ease of the growth-inhibiting effect by the addition of nuirients to test water in a previous method. Since a previous bioassay method is indispensable to add nutrients to test water to avoid the nutrient limitation for the growth, it was revealed that a previous method cannot make the appropriate evaluation of chemical toxicity. Therefore It was considered that the novel bioassay method is useful to apply for the ecological impact assessment of cheinicals because the method is possible to evaluate a growth-inhibiting effect without the addition ofnutriets to test water.
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  • Tsukasa SASAKI, Toni WATANABE, Takayuki MIURA, Yoshifumi MASAGO, Satos ...
    2008 Volume 45 Pages 169-177
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    A risk evaluation framework of waterbome infectious diseases based on seroprevalence was developed and used to evaluate risk of infection by Campylobacter jejuni, Helicobacter pylori and adenoviruses in two villages in rural Cambodia. As the result, it was revealed that no outbreak of campylobacteriosis occurred in recent years.It was also revealed that almost all villagers would be infected by adenovirus in the first five years of their lives. As for H pylori infection, a high annual risk of infection (8 to 10%) was estimated and drinking water contamination with total coliform was found to be a significant risk factor (OR=5.29, 95 % C.I.=1.17 to 23.9). Although a part of villagers drank well water heavily contaminated with arsenic, the effect of arsenic on disturbing their production of serum antibody against H pylori was negligible.
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  • Diverticulum of Japanese Oyster, Crassostrea gigas
    Chie OKUMURA, Yoshifumi MASAGO, Daisuke SANO, You UEKI, Tatsuo OMURA
    2008 Volume 45 Pages 179-186
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    A new virus elution method from digestive diverticulum of Japanese oyster, Crassostrea gigas, using enzymatic virus elution (EVE) method was developed using poliovirus 1 as a surrogate. Among three enzymes, amylase, lipase and pepsin, lipase and amylase were effective for elution of viruses from digestive diverticulum collected in winter, with total recovery efficiency of 11% and 9.6%, respectively. Lipase was also effective for virus elution from digestive diverticula collected in spring when oysters are in reproductive phase and contain more fat in their digestive diverticula. In conclusion, the EVE method using lipase is very effective in quantitative evaluation of virus accumulation by oysters and its seasonal trends.
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  • Eri NAKAO, Kazunori NAKANO, Munehiro NOMURA, Nobuo CHIBA, Osamu NISHIM ...
    2008 Volume 45 Pages 187-194
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Actual situations concerning the distribution of antibiotic-resistant bacteria in aquatic environments around livestock area in Miyagi prefecture were investigated. Four selective plates to isolate bacteria derived from feces indicating wastewater pollution by livestock farms and indigenous bacteria in the aquatic environments were used to examine the existing ratio of antibiotic-resistant bacteria to ampicillin, kanamycin, oxytetracycline and chloramphenicol. As a result, resistant bacteria to these antibiotics were extensively found in indigenous bacteria as well as intestinal bacteria derived from livestock farm. Their distribution was confirmed not only at down-flow area of livestock farm, but also at up-flow area without livestock farm. The relationships between the ratio of antibiotic-resistant bacteria and wastewater pollution by livestock farms were indicated by correlation with intestinal bacterial number. Although some indigenous antibiotic-resistance was observed, the ratio of antibiotic-resistant bacteria was unusually high at some investigation sites. Potential causes for high ratio of antibiotic-resistant bacteria were discussed.
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  • Rahul R. UPADHYE, Daisuke INOUE, Tomonori ISHIGAKI, Kazunari SEI, Mich ...
    2008 Volume 45 Pages 195-202
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    Eubacterial communities and bacterial pathogens occurring in the leachates collected from three full-scale landfills in mesothermal area of Japan were analyzed using DNA microarrays targeting approximately a thousand eubacterial and pathogen species/groups. The leachate samples showed almost similar eubacterial compositions with marginal variations. Comparison of the results with precedents suggested that the predominant eubacterial populations in the landfills may be generally similar in East and Southeast Asia, irrespective of the climate zone. Analysis of the bacterial pathogens showed that the three leachates included a total of 44 species/groups of bacterial pathogens and 26 species/groups including Francisella, a frank zoonotic pathogens causing a serious health risk, and other high-risk pathogens were commonly found. In addtion, the 2 leachate samples from the landfills, where organic wastes such as sludge and raw garbage were mainly disposed, had 15 specific pathogens. It was suggested that sludge can increase the variation of the pathogens occurring in landfill leachates. Overall, results of this study posed some insights into the underlying microbial ecology in the landfill and the possible microbiological health risks associated with the landfill leachate.
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  • Aya SAKAKI, Kayoko OKUYAMA, Kanji NAKAMURA
    2008 Volume 45 Pages 203-210
    Published: November 28, 2008
    Released: June 27, 2011
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    Impacts of Cupriavidus necator KT1 on indigenous bacterial community in river water were examined by batch experiments. Three sets of river water samples, that contain strain KT1 of 1, 10, and 50% of total bacteria in river water, were prepared respectively. Changes of microbial community composition were analyzed. A control analysis was also conducted without KT1 addition. Only the 16S rRNA gene of strain KT1 added was decreased remarkably within 5 days. As a result, indigenous bacterial community composition was restored in a short time. A grazing experiment was carried out by using strain KT1. A high concentration of strain KT1 culture was added to a river water. A rapid decrease of strain KT1 was observed, and a flagellate was found to graze strain KT1. The flagellate may play an important role in preserving a natural ecosystem.
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  • Kiyo Hasegawa-KURISU, Michitaka HAMA, Keisuke HANAKI
    2008 Volume 45 Pages 211-217
    Published: November 28, 2008
    Released: June 27, 2011
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    It was investigated whether GST (glutathione-S-transferasaec) t ivity in plant leaves can be used as a biomarker of air pollution or not. As the first step, effective protein extraction method and temperature of GST-activity measurement were checked. Using the determined extraction and measurement method, GST activities of Pothos (Epipremunum aureum) exposed by road-or tobacco-pollutants were analyzed. The leaves exposed by environmental tobacco smoke in about one month showed significantly high GST activities than that of the control. It indicated the possibility of GST in plant leaves as a biomarker of air pollution, but further investigation especially about influencing factors is needed.
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  • ANDRIANISA Harinaivo Anderson, Ayumi ITO, Jun-ichi MIURA, Jiro AIZAWA, ...
    2008 Volume 45 Pages 219-224
    Published: November 28, 2008
    Released: June 27, 2011
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    In this study, the isolation of arsenite oxidising bacteria from activated sludge was investigated through subculture using the mineral medium contaning high concentration of arsenite. Arsenite was biologically oxidised to arsenate by bacteria in the activated sludge and two kinds of bacteria were isolated. One of the bacterium isolated from the activated sludge could grow by oxidising arsenite and was most closely related to Ensifer adhaerens (homology: 99.9%). The other could not oxidize arsenite and was related to Microbacterium keratanolyticum (homology: 99.5%). The oxidation rate of arsenite by the isolated arsenite oxidising bacteria followed the Michaelis-Menten's model and the maximum reaction rate and the Michaelis constant were 1.74 × 10-9μg/cell/min and 415μg/L, respectively. Furthermore, the coexistence of lactate as an organic carbon source accelerated the oxidation rate of arsenite by the bacteria.
    It was concluded that the arsenite oxidising bacterium isolated in this study can be utilized for the remediation of groundwater and wastewater contaminated with arsenite.
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  • Hiroyasu SATOH, Motoharu ONUKI, Takashi MINO
    2008 Volume 45 Pages 225-232
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    For the analysis of microbial population in activated sludge samples, significant cost and time are spent for the extraction of DNA from cells. In the present study, DNA was first extracted from samples by sonication, and the crude extract was subjected to PCR (polymerase chain reaction). When the sonicated sample was diluted to around 1, 000 to 10, 000 times, PCR products were obtained. For the same sample, DNA was extracted by the present method and one of the commersial DNA extraction-purification kits using beads beating, and was subjected to T-RFLP (Terminal-Restriction Fragment Length Polymorphism) analysis targetted at a partial sequence of 16SrRNA gene. While the obtained fragment patterns had differences, it was found the present method can be applicable for at least some part of bacteria. It is worth to improve the present method by further research and development, as it is extremely simple.
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  • Kazuo SUEOKA, Motoharu ONUKI, Hiroyasu Satoh, Takashi MINO
    2008 Volume 45 Pages 233-240
    Published: November 28, 2008
    Released: June 27, 2011
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    Stable isotope probing of RNA (RNA-SIP) was applied for the identification of phenol-assimilating microorganisms in activated sludge treating a synthetic coke oven wastewater. The RNA-SIP method is a culture-independent method using stable isotope-enriched substrates that be able to link the identity of microorganisms with their function in the environment. The activated sludge was fed with 13C-labeled phenol (300 mg per 1) and ribonucleic acids of phenol-assimilating microorganisms were labeled with 13C. The 13C-RNA was extracted from the samples, fractionated by ultracentrifugation, and analyzed by terminal restriction fragment length polymorphism, and the selected fractions were further analyzed by cloning and sequencing. These analyses showed that the bacteria assimilating 13C derived from the 13C-labeled phenol were the Betaproteobacterial Thauera genus, the Gammaproteobacterial Marinobacterium and Halomonas genera, and the Actinobacterial Propionibacterium genus.
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  • Kazuyuki SUZUKI, Takeshi YOSHIOKA, Yoshiro ONO
    2008 Volume 45 Pages 241-249
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    This study is an attempt at development of low-cost and effective technologies for leachate treatment using cover soil. A mixture of Andisol and waste iron powder was selected as cover soil for adsorption of heavy metals in landfill leachate. Batch adsorption experiments were performed to assess the performance of Andisol and waste iron powder for heavy metal adsorption under various conditions (pH, temperature, etc.). The adsorption of heavy metals on both adsorbents was well described using the Freundlich isotherm equation model. Andisol and waste iron powder have high adsorption capability. For pH 4-6, the Freundlich constant KF of both adsorbents remained almost constant. The Freundlich constant KF, which reflects the adsorption capacity, increased with increasing temperature to 35, 3 K. Thermodynamic parameters were calculated. The thermodynamic parameters of both adsorbents showed the endothermic and spontaneous nature of the process. Using these results, it was concluded that the mixture is useful as cover soil for removal of heavy metals from leachate under oxidative condition. Column adsorption experiments were performed using the mixture for determination of kinetic parameters under a dynamic adsorption process. The Bohart and Adams model showed a better fit for Cu, Pb, and Zn. In the bed depth service time (BDST) model, the adsorption capacity N0 and rate constant k are obtainable.
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  • Taishi YAMASHITA, Satoshi MIZUTANI, Yoshinori KANJO
    2008 Volume 45 Pages 251-257
    Published: November 28, 2008
    Released: June 27, 2011
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    Water-washing treatment for MSW incineration bottom ash and fly ash were studied. Column test and the availavility test were performed in order to evaluate the long-term leaching behavior and washing effect. Increasing the frequency of washing is more effective for promoting elution rather than a liquid per solid ratio (L/S) or elution time. The cumulative amount of leaching in a column test was controlled to about 1/2-1/10 by water-washing for TOC and soluble salts such Na, Ca, K, and Cl-. On the other hand, removing heavy metals such as Cd were difficult.
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  • Nobuo TAKEDA, Masaki TAKAOKA, Kazuyuki OSHITA
    2008 Volume 45 Pages 259-270
    Published: November 28, 2008
    Released: June 27, 2011
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    This study measured hazardous materials, including dioxins, mercury, and hexavalent chromium compounds, in the flue gases, fly ash, and bottom ash from four crematoriums in Japan, to evaluate the emissions from crematoriums.
    The toxic equivalent concentration (normalized by 12% O2) of dioxins in the flue gases from crematoriums ranged from 0.00012 to 1.2ng-TEQ/m3N. The estimated maximum emission inventory of dioxins from crematoriums was 1.1 g-TEQ/year, which is less than one-filih ofthe present emission inventoiy. Although mercury in flue gases from crematoriums was under the minimum limit of determination using the JIS K0222 method, Hg0 from dental amalgam contributed significantly to the total mercury emissions from crematoriums based on a continuous mercury speciation analyzer, as in our past study. The hexavalent chromium compounds leached from all ash samples exceeded the Japanese environmental quality standards for soil by 180 to 1, 200 times. Therefore, countermeasures against hexavalent chromium compounds in the ash from crematoriums are required.
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  • Alonso Montero, Yasumasa TOJO, Takayuki MATSUO, Toshihiko MATSUTO, Mas ...
    2008 Volume 45 Pages 271-278
    Published: November 28, 2008
    Released: June 27, 2011
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    The final disposal ratio of mixed construction and demolition waste (MCDW) remains high in Japan, while progress has been made in the recycling of other construction and demolition waste. Sorting facilities are expected to play an important role in better management of MCDW. In this study, the feasibility of sorting facilities for the separation of material and of pretreatment for fmal disposal was investigated by conducting a batch experiment at a real operational facility. The material flow of each output fraction was determined based on the mass distribution and on analysis of the ignition loss and metal content. The separation of organic matter and ferrous metal achieved by the sorting process was excellent; almost 70% was separated out for recycling and did not go for disposal. Although the distribution ratios of heavy metals, such as Pb and Zn, sent to landfill were still high, their content little changed from the condition of the original mixed waste. The process of sorting MCDW achieved reduction of mass for disposal, reduction of the organic load directed to the landfill, and the diversion of iron from MCDW to recycling.
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  • A CGE Model in the context of the Household Production function
    Atushi KOIKE, Yumiko YAMAGUCHI, Yoshihiko HOSOI
    2008 Volume 45 Pages 279-287
    Published: November 28, 2008
    Released: June 27, 2011
    JOURNALS FREE ACCESS
    The Local governments in Japan should make a plan to dispose to the municipal solid waste. The waste management law provides that local government can collect the cost for waste management to the people. By this content, the case of introducing garbage fee by local government was increased. Especially, waste disposal charge will be more populer. This study aims to analyze the economic effects by the waste disposal charge in Tottori prefecture. We builded a CGE Model in the context of the household production function. Especially, we build consumer behavior model in oder to deal with waste reduction activity time. The conclusion of this study is that waste disposal charge is effective municipal solid waste reduction.
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  • Katsuyuki TAKAHASHI, Taiki SATO, Jun NAITO, Seiji MUKAIGAWA, Koichi TA ...
    2008 Volume 45 Pages 289-294
    Published: November 28, 2008
    Released: June 27, 2011
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    Water purification using a pulsed power discharge in water and ozone generated by dielectric barrier discharge (DBD) have been investigated experimentaly. Solutions contained Acid Red 1 and Acid Blue 64 were used as a specimen. A stacked Blumlein line pulsed power generator and wire-to-plane electrode was employed to generate the discharge in the water. The ozone of 1500 ppm cocentration was generated using pulse modulator driven coaxial cylinder DBD reactor and was injected to the solution. The electric powers consumed in reactors were 3 W and 8 W for water discharge and DBD, respectively. Acid Red 1 was successfully decolorized with 30 min of the ozonation process. The peak of the absorbance spectra shifted to higher value through the discharge in the water. The decoloration efficency of Acid Blue 64 by the ozonation process was about 1.1 times higher than that using the discharge in the water. The total organic carbone (TOC) removal was achieved to about 20% by the ozonation process.
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  • Qiong ZHANG, Takaya HIGUCHI, Masahiko SEKINE, Tsuyoshi IMAI
    2008 Volume 45 Pages 295-300
    Published: November 28, 2008
    Released: June 27, 2011
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    Palygorskite, which is one of magnesium aluminum silicate, was investigated as adsorbent to adsorb ammonia gas in this study. The palygorskite was pretreated with HCl, HNO3 or NaOH with different concentration, temperature and reaction time. Raw palygorskite and pretreated ones were characterized with specific surface area by Brunauer-Emmett-Teller method, crystal structure by X-ray diffraction and metal dissolution by inductively coupled plasma-optical emission spectroscopy. Adsorption experiments were carried out at room temperature with an initial ammonia concentration in the range of 150-3000 ppm in nitrogen carrier gas. The adsorption capacity of ammonia was investigated by the 10% breakthrough time. The results showed that palygorskite had excellent adsorption property for adsorbing ammonia. The sample HCl-352 pretreated with 3 mol/l of HCl at 50°C for 24 hours had the highest adsorption capacity of 17.2mg/g.
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  • Koji KIMURA, Shigeo FUJII, Shuhei TANAKA, Yong QIU, Munehiro NOZOE
    2008 Volume 45 Pages 301-308
    Published: November 28, 2008
    Released: June 27, 2011
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    Adsorption removal of eight per-fluorinated compounds by powdered activated carbon was studied. In single-solute solutions, adsorption equilibrium constant K were calculated as 22.33 for PFOS, and 14.48 for PFOA. Substances with longer carbon chain were removed better, suggesting the relation of adsorption removal with their hydrophobicities. In mixed solution of the eight compounds, the removed amount of three compounds: PFDA, PFDoA, and PFOS was decreased to 80 % of single-solute solution, whereas for the other five: PFHxA, PFHpA, PFOA, PFNA, and PFHxS, the amount decreased to less than half. The effect of dissolved organic matters was also investigated by using Lake Biwa water as the solvent of the mixed solution. The removal of PFOS and PFHxS was not greatly affected and the removed amount decreased by 60%. However, the other five compounds were scarcely removed, showing irregular temporal concentration changes.
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  • Naoya ANDO, Yoshihiko MATSUI, Taku MATSUSHITA, Koichi OHNO, Hiroshi SA ...
    2008 Volume 45 Pages 309-315
    Published: November 28, 2008
    Released: June 27, 2011
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    Batch adsorption experiments using powdered activated carbon (PAC) and submicron-powdered activated carbon (S-PAC) were conducted for natural organic matter (NOM), polystyrene sulfonates (PSS) and polyethylene glycols (PEG). Pulverization of PAC to submicron size increased adsorption capacity of NOM. Increase in adsorption capacity tended to be substantial for compounds with higher molecular weight, but highly depended on the type of compounds. The homogeneous surface diffusion model (HSDM) simulation revealed that factors mainly contributing to the increase in adsorption kinetic with the pulverization also depended on the type of compounds: the predominant factor for PSS was the increase in adsorption capacity, whereas that for PEG was the increase in specifc surface area of the activated carbon.
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  • Ken Hattori, Toshihiro Kochizawa, Yusuke Watanabe, Madan Tandukar, Ken ...
    2008 Volume 45 Pages 317-324
    Published: November 28, 2008
    Released: June 27, 2011
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    The objective of this study is to evaluate applicability of DHS reactor to nitrification process receiving a high strength ammonium influent. The most prominent advantage of DHS reactor is no need for external aeration because sponge carriers are exposed to air. DHS reactor in this study was operated with an artificial wastewater composed of ammonium-nitrogen solely (completely organic free) at ambient temperature. The total experimental period of 350·days was divided into 4 phases according to ammonium-nitrogen loading rate. The maximum nitrification rate of 1.78 kg-N·m-3·d-1 was observed at a HRT of 6 h and at an ammonium-nitrogen loading rate of 2.00 kg-N·m-3·d-1. The maximum oxygen uptake rate was estimated from nitrogen elimination rate to be 66 g-O2·g-VSS-1·d-1. Nitrification potential of DHS reactor was verified to be comparable to other types of nitrification processes equipped with external aeration. There is a need of further investigation to enhance the nitrification performance by overcoming the restriction of partial oxygen permeation into carrier-sponge inward depth.
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  • Ryoko TANIGUCHI, Akinori IGUCHI, Tadashi TAGAWA, Shinichi YAMAZAKI, No ...
    2008 Volume 45 Pages 325-331
    Published: November 28, 2008
    Released: June 27, 2011
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    A UASB (Up-flow Anaerobic sludge Blanket)-DHS (Down-flow Hanging sponge) system has been operated for degradation of wastewater containing polyvinyl alcohol (PVA), the water-soluble polymer which is commonly used in textile industry. Anaerobic organisms has been applied to the UASB reactor to investigate the biodegradation of easily decomposable organic matter and depolymerization of PVA.
    The results of clone analysis targeting all bacterium of 16S rRNA, Bactemidetes were predominant species in the UASB reactor. Putative PVA degrading bacteria such asAlcaligenes sp., Pseudomonassp., Azoareussp., Xanthomonassp. were detected in the DHS reactor.
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  • Myung Yeol LEE, Taira HIDAKA, Hiroshi TSUNO
    2008 Volume 45 Pages 333-339
    Published: November 28, 2008
    Released: June 27, 2011
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    Among various methods used for the treatment of kitchen garbage and excess sludge, anaerobic digestion is a promising technology with energy recovery, but required to be more effective. An anaerobic digester system that consists of an acidogenic reactor operating at hyperthermophilic condition and a methanogenic reactor in series was discussed. Lab-scale reactors were operated continuously fed with artificial kitchen garbage or co-substrate composed of artificial kitchen garbage and excess slude. At the acidification step, protein solubilization ratio at 70°C was higher than that at 55°C. It was suggested that the process composed of acidogenesis at 70°C and methanogenesis at 55°C is useful to increase methane production and process stability. By batch experiments, it was proved that this process had both biological and physical effects, and had higher treatment performance than heat treatment only.
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  • Kazuya KOMATSU, Hidenari YASUI, Yu-You Li, Tatsuya NOIKE
    2008 Volume 45 Pages 341-348
    Published: November 28, 2008
    Released: June 27, 2011
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    Recently, anaerobic digestion is re-apprised as treatment process of municipal sludge and many studies are conducted to develop new technologies to improve digestion efficiency. Inorganic ratio in digested sludge increases as more organic components are degraded by improvement of digestion efficiency, and their dissolution/precipitation have more effects on the process performance, such as dewaterability of digested sludge. However, inorganic dissolution/precipitation reaction is excluded in modeling of anaerobic digestion process due to the complexities of the process. Since digested sludge analysis revealed that phosphoric anhydride occupied one-fourth of total ash content and main soluble components were PO4-P, Ca and Mg, the mathematical model for prediction of inorganic dissolution/precipitation in anaerobic digestion was composed based on the reported prediction model of recycle phosphorus loads from anaerobic digestion. By considering the solubility products of precipitated phosphate and modifying release rate of Ca and Al from feed sludge components in the reported model, it was possible to calculate soluble PO4-P, Ca and Mg concentration in the digested sludge based on inorganic composition of feed sludge and digester operating conditions.
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  • Boyang LI, Takaya HIGUCHI, Masao UKITA, Tsuyoshi IMAI, Masahiko SEKINE
    2008 Volume 45 Pages 349-353
    Published: November 28, 2008
    Released: June 27, 2011
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    Biowaste, the separately collected organic fraction of municipal solid waste, can be reused for soil conditioning after composting. In this study, a series of field investigations was conducted on human health essential minerals, Ca, Fe, Mg, Mn, Zn, Cu and toxic heavy metals, Pb, Cr, Cd in soil which have been amended with biowaste composts only or amended with chemical fertilizer plus lower composts. The results show that the biowaste compost applications likely led to the increases of mineral elements in soils for Ca, Mg, Mn and Zn excluding some exception. It was also found that biowaste compost applications have shown the tendency of the increases of bio-available forms of Fe, Mn and the reverse situation for Mg. Comparison of supply ratios (SR = bio-available content/total content×100%) of all elements in compost-amended and no amended soils showed that the leachability of Fe, Mn, Zn, Pb was slightly increased by biowaste compost application, and less changed for other elements.
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  • Takahiro Imai, Daisuke Sano, Yoshifumi Masago, You Ueki, Kensuke Fukus ...
    2008 Volume 45 Pages 355-360
    Published: November 28, 2008
    Released: June 27, 2011
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    Capsid gene sequences of norovirus GII were acquired from patients of gastroenteritis, primary-treated wastewater, activated sludge, secondary-treated wastewater, river water, seawater and oyster in geographically close areas between 2001 and 2006. Most of the norovirus GII genes acquired from gastroenteritis patients were mainly categorized into GII.3 and GII.4. On the other hand, diverse genotypes of norovirus GII including GII.2, 3, 4, 5, 10, 11, 14and 15 were obtained from environmental samples. Amino acid sequences of norovirus GII.4 obtained in this study were compared with that of norovirus GII.4 Bristol. As a result, amino acid substitutions were observed in the 8th (Ala), 9th (Asn), 15th (Ala) and 54th (Asn) residues. The analysis of amino acid substitutions and investigation of the appearance of norovirus mutants could be useful to understand the dynamics of norovirus in human society.
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  • Masaaki KITAJIMA, Yukinobu TOHYA, Koichi MATSUBARA, Eiji HARAMOTO, Ets ...
    2008 Volume 45 Pages 361-370
    Published: November 28, 2008
    Released: June 27, 2011
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    Human noroviruses (NoVs) are a major cause of viral gastroenteritis outbreaks worldwide and commonly transmitted via the fecal-oral route through contaminated food or water. Due to the lack of cell culture system for NoVs, little knowledge is available on the resistance of NoVs to various disinfectants. In this study, cultivable murine norovirus (MNV) was used as a surrogate to evaluate resistance of NoVs to chlorination in drinking water supply system. MNV, NoV, and poliovirus type 1 (PV1) were inoculated into treated water collected from a drinking water treatment plant, followed by free chlorine disinfection. MNV was inactivated more than 99.99%(4 log) with the Ct value of 3 mg/L-min, showing less resistance to free chlorine than PV1. Based on TaqMan real-time RT-PCR analysis, the reduction rate of NoV genogroup II (Lordsdale strain) was comparable to that of MNV. These results indicate that NoVs are not highly resistant to free chlorine disinfection compared with other enteric viruses and that NoV-infection via drinking water supply system can be controlled with adequate chlorination.
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  • Eiji HARAMOTO, Yuji YONASHIRO, Michihiro AKIBA, Atsushi HASHIMOTO, Shi ...
    2008 Volume 45 Pages 371-377
    Published: November 28, 2008
    Released: June 27, 2011
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    The objective of this study was to determine the occurrence of Cryptosporidium and Giardia in river water used for drinking water. Twenty-three river water samples were collected at 7 sites in tributary rivers of the Tonegawa River basin in Japan from October 2007 to February 2008. Cryptosporidium and Giardia were detected in 21 (91%) and 18 (78%) of the 23 samples (10 liters each), showing the highest concentration of 790 oocysts/10 L and 37 cysts/10 L, respectively. A single Cryptosporidium oocyst was isolated from the concentrated river water sample by using micromanipulation technique, followed by DNA extraction and nested PCR of the 18S rDNA gene. Fifty-six (15%) out of 376 single-oocyst samples were positive for the Cryptosporidium 18S rDNA gene, and subsequent direct DNA-sequencing revealed the presence of four genotypes: C. suis (48 samples, or 8 strains), C. andersoni (5 samples, or 4 strains), C. pig genotype II (2 samples, or 2 strains), and C. meleagridis (1 sample, or 1 strain).
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  • A Case Study in Gifu City
    Yasuhiro SASAJIMA, Chihiro YOSHIMURA, Fusheng LI
    2008 Volume 45 Pages 379-387
    Published: November 28, 2008
    Released: June 27, 2011
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    This study focused on the relationship between land use and coliphage concentration in rivers in Gifu city. We sampled river water at 20 sites along four urban rivers and analyzed water chemistry and concentrations of F-RNA and somatic phages and Escherichia coli. Coliphage concentrations were the highest along agricultural land followed by urban area and forest. River section receiving treated sewage water showed lower coliphage concentration than that without treated sewage water in urban area. This study revealed that pathogenic virus concentration is higher in suburb, agricultural and residential areas, than in the city center, which implied diffuse pollution of pathogenic virus in water environment.
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  • Motonari KAMIMURA, Nobuo ARAKI, Takemasa HAMAGUCHI, Shinichi YAMAZAKI, ...
    2008 Volume 45 Pages 389-398
    Published: November 28, 2008
    Released: June 27, 2011
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    We have proposed a newly sewage treatment system by combining a two-step of anaerobic UASB (for removal of organics and denitrification) and an aerobic biofilm reactor in order to diminish energy requirements and excess sludge production as enhancing sulfur-redox cycle. Analysis of microbial community structure on denitrifying bacteria was carried out by combining of molecular tolls and vial activity tests of retained sludge in the second UASB. PCR-denaturing gradient gel electrophoresis (DGGE) was revealed that both Thiobacillus denitrificans and Acidovorax avenae coexisted as a predominant species of nitrate-reducing sulfur-oxidizing bacteria (NR-SOB) and heterotrophic denitrifying bacteria (ODB), respectively. Hydrogen-utilizing sulfate-reducing bacteria (SRB) also present in the UASB as establishing symbioses through sulfur compounds with NR-SOB. Additional influent of wastewater to the UASB likely activated not only ODB but also SRB, leading growth of NR-SOB. It was estimated that NR-SOB contributed 80% of over all of nitrogen removal from the UASB, enabling the high denitrifying efficiency of the whole system.
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  • Yasuto TANABE, Tomonori KINDAICHI, Noriatsu OZAKI
    2008 Volume 45 Pages 399-405
    Published: November 28, 2008
    Released: June 27, 2011
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    Benzene and polycyclic aromatic hydrocarbons (PAHs) are toxic chemical compounds in the petroleum-contaminated site. Bioremediation isuseful technique that can remove these chemical compounds. In order to establish bioremediation technique, it is important to identify degradation bacteria. In this study, to enrich PAHs-degrading bacterial community, activated sludge was incubated with PAHs (benzene, naphthalene, phenanthrene) as the sole source of carbon. Phylogenetic analysis and MAR-FISH analysis revealed that Acinetobacter sp. is capable of degradation of benzene and member of Betaproteobacteria and Gammaproteobacteria are capable of degradation of naphthalene and phenanthrene.
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  • Nobuo HARATA, Fusheng LI, Maya ITO, Yoshihiro KATAMINE, Chihiro YOSHIM ...
    2008 Volume 45 Pages 407-414
    Published: November 28, 2008
    Released: June 27, 2011
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    Microorganism inhabited in river water system is an important factor affecting river ecosystems and river water qualities. In this study, the density of microorganisms in Nagara River water system was evaluated by real time PCR method and the plate culture method for river water and the riverbed sediment field collected from the mainstream of the Nagara River and its seven major tributaries. The results indicated that the density of microorganisms in the river water phase increased as water flowed downstream, however, that in the riverbed sediment phase did not change significantly. Water quality seemed to be in close relation with the density of microorganisms. In addition, the relationship between total microorganisms (defected by the real time PCR method) and viable cells (defected by the plate culture method) differed with field study points, suggesting that microorganisms were affected by water qualities at those study points and seasons.
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