ENVIRONMENTAL ENGINEERING RESEARCH
Online ISSN : 1884-829X
Print ISSN : 1341-5115
ISSN-L : 1341-5115
Volume 30
Showing 1-39 articles out of 39 articles from the selected issue
  • Toshihiro KOMATSU, Tatsuya NOIKE
    1993 Volume 30 Pages 1-7
    Published: November 29, 1993
    Released: March 17, 2010
    JOURNALS FREE ACCESS
    Anaerobic digestion is extremely attractive for the treatment of easily degradable high strength wastewaters from sewege sludge and various in dustries because of the energy recovery by methane productionand low excess sludge production as compared with aerobic treatment. Recently, anaerobic digestion was modified by use of two-phase system and membrane separation. However, little is known on the effects of accumulated biomass in two-phase anaerobic digestion by use of membrane separation during start-up phase.The purpose of this study is to examine the effects of accumulated biomass on the acidogenic phase of two-phase anaerobic digestion. It can be concluded from the results of this study that:(1) The biomass and macromolecular substances were kept at high concentrations in the bioreactor by the membrane separation module.(2) The biomass concentration was stable at day 200.(3) The concentrations of VFAs decreased in the following order: acetic>propionic>i-valeric>i-butyricand varied n-butyric acid during cell growingtime, but on the other hand, when cell biomass concentration was kept at steady state the order was as follows: acetic>propionic>i-valeric>i-butyric>n-butyric acid.
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  • Zhen Jia ZHANG, Hiroshi NAKANISHI, Masao UKITA, Hasayuki FUKAGAWA
    1993 Volume 30 Pages 9-15
    Published: November 29, 1993
    Released: March 17, 2010
    JOURNALS FREE ACCESS
    In this paper the mixing characteristics and their influencing elements in a gas-lift bioreactor with bio-gas circulation were analysed by means of tracer test. The results showed that the sludge concentration in the reactor influenced the mixing state for the bypass and the deadspace increased with increasing of the sludge concentration. The volume utilizing efficiency (ηv) of reactor decreased from 89.9% to 82. 5%, and the bypass rate (1-ηt) increased from 11.5% to 23.1%, when the sludge concentration increased from 14.6gl-1 to 21.8gl-1. Therefore it can be deducted that it is unilateral to increase simply the sludge concentration of reactor in an anaerobic contact process. The bypass is main factor for the decline of treatment efficiency of reactor.
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  • Nobuo ARAKI, Hideki HARADA, Kiyoshi MOMONOI
    1993 Volume 30 Pages 17-25
    Published: November 29, 1993
    Released: March 17, 2010
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    Effect of particulate organic loading on performance of anaerobic fluidized bed reactor was investigated during a start-up period. Experiments were conducted by in parallel operating two laboratory-scale reactors with an identical size fed with a synthetic wastewater containing two different strengths of cellulose: 25% and 50% of the influent COD (referred to as 25%-run and 50%-run). Organic loadings were increased stepwise throughout 140 days from 0.5 to 10g·l-1·d-1in the 25%-run, and from 0.5 to 5 g·l-1·d-1 in the 50%-run. The influent cellulose strength caused a distinctive difference in the behaviors of cellulose retainment and degradation in the reactors. At the low strength (as for 25%-run) cellulose particles tended to be captured by attachment onto biofilm surfaces and then they were slowly but eventually degraded. On the other hand at the high strength (as for 50%-run) cellulose was more subject to being entrapped into inter-lattice voids between bioparticles one another, rather than attached onto biofilms themselves. A subsequent extrusion of cellulose particles entrapped in bed voids from the reactor was associated with a sharp decline in bed expansion with in the initial 20 days. Cellulose accumulation in biofilms in the early stage of the 25%-run accounted for 16% of MLVSS, while in the last stage of the 50%-run it attained 36% of MLVSS. Cellulose accumulation affected significantly biofilm density, rather than biofilm thickness. The biofilm density decreased with an increase in cellulose content of biofilm. Bioparticles located at the upper portion of reactor had tendency to have larger thickness as well as higher cellulose content.
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  • Hiroshi TSUNO, Masasumi KAWAMURA, Isao SOMIYA, Zenkon ROU
    1993 Volume 30 Pages 27-38
    Published: November 29, 1993
    Released: March 17, 2010
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    Fluidized-bed GAC (granular activated carbon) anaerobic reactor was applied to treat artificial wastewater which contains high concentration of phenol as well as acetic acid. Organic loadings were changed from 2 to 40 gCOD/kgGAC.day by changing concentrations of organics (phenol concentration from 500 to 2, 000 mg/L) and hydraulic retention time from 2 to 0.2 days based on the fluidized-bed volume. The operation of the reactor was successfully started without any dilution of the wastewater and the reactor could respond without any deterioration of treatment efficiency to shock load by the adsorption ability of GAC used as attached medium. COD and phenol removal efficiencies were kept more than 95%. GAC adsorption capacity consumed at start-up operation and shock load was biologically regenerated before and during stable operation. Biomass in the reactor was from 0.24 to 0.64 mgDNA/gGAC, which corresponds to 4, 000-10, 000 mgVSS/L based on the fluidized-bed volume.
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  • Shigeki UEMURA, Hideki HARADA
    1993 Volume 30 Pages 39-49
    Published: November 29, 1993
    Released: March 17, 2010
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    A thermophilic UASB reactor was operated for a period of more than six month by feeding a synthetic wastewater composed of sucrose. Well-settleable granulated sludge with a diameter of 2-3 mm developed successfully after 100 days operation from a start-up. Characterization of thermophilic granules was made with respect to morphological structure and methanogenic activity. The granule showed a double-layered structure. The exterior layer was composed of a sponge-like material, while crystalline precipitates existed in abundance inside the granule (referred to as the core). A major component of the precipitates formed in the core was confirmed to be calcium carbonate, in the form of not only aragonite but also calcite. The presence of calcium-bound phosphorus in the core was three times as large as that in the exterior layer. Methanogenic activities from acetate and hydrogen increased with increasing vial-test temperature from 55°C to 65°C: 1.43 to 2.36 and 0.85 to 1.11kgCH4-COD·kgVSS-1·d-1, respectively, for acetate and hydrogen. On the other hand, methanogenic activity from propionate remained unchanged in that temperature range (0.1-0.12kgCH4-COD· kgVSS-1·d-1). The methanogenic activity from propionate was considerably lower than that from acetate or hydrogen, indicating that the propionate degradation is a ratelimiting step in the thermophilic condition. The acetate utilization rate of the granules was significantly inhibited by the presence of hydrogen. This indicates that a large extent of acetate conversion to methane was performed by a syntrophic association between acetate-oxidizers and hydrogenotrophic methanogens.
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  • Aloice W. MAYO, Atsuya NOIKE
    1993 Volume 30 Pages 51-60
    Published: November 29, 1993
    Released: March 17, 2010
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    This paper presents the effect of organic loading rate on the carbon distribution in mixed algal-bacteria fed batch culture. Glucose used as a source of organic carbon was fed daily in granular form to provide input concentration ranging from 25-700 mg/l. Results show that glucose was largely converted to biomass in aerobic reactors. In anaerobic reactors however, glucose was mainly converted to gases and volatile fatty acids (VFAs). The growth of biomass in anaerobic reactors were affected by accumulation of VFAs. The maximum biomass specific growth rate, μmax, and substrate saturation constant, K were 0.44 d-1 and 135 mg/l respectively. The specific dissolved inorganic carbon accumulation increased as glucose loading rate increased. However, because of VFA accumulation in anaerobic reactors, pH dropped resulting in shift of equilibrium between H2CO3∗(H2CO3∗+CO2(aq) ), HCO3 and CO32-in favor of H2CO3∗ production, most of which was released as CO2 (g) to the atmosphere.
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  • Youngjae KIM, Toshihiko MATSUTO, Nobutoshi TANAKA
    1993 Volume 30 Pages 61-71
    Published: November 29, 1993
    Released: March 17, 2010
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    One and half year long survey was done for Sapporo RDF plant, in which RDF is produced from wood, paper, plastics commercial & industrial refuse. Physical composition of raw materials were determined for samples taken at outlets of the shredders, the storage silos and the mixingfeeder, and properties of RDF, such as calorific value, moisture and ash content, were measured. Though large fluctuations in the compositions and RDF properties were found on an hourly basis, RDF properties except bulk density, were rather stable on monthly basis. The calorific value of RDF increases as the plastics content increases, or as the incombustible content decreases. The bulk density of RDF increased as the moisture and wood content decreased. The sampling and measuring method employed inthis study can be applied to other RDF plants, and the mass flow rate in the plant was determined by least square method using the composition data and plant operation data.
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  • Tomonori KAWAKAMI
    1993 Volume 30 Pages 73-80
    Published: November 29, 1993
    Released: March 17, 2010
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    Investigation conducted in 1992 and 1993 showed that the pH values in the lakes around the top of Mt.Norikura decreased compared with those in 1985. The water in all these lakes had low alkalinity values, low ion content and low pH values. An analysis of the ion balance between rain and water in Lake Tsurugaike revealed that neither ion exchange of H+ for Ca2+ in sediments nor biological reduction of SO42- took place. During the snow melting periods, there was a decrease in the concentrations of major ions in Lake Tsurugaike and an increase in pH values. This indicates that Tsurugaike was strongly influenced by the initial fraction of meltwater containing highly concentrated ions released from snow pack.
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  • Junichi ICHIYANAGI, Kohki GOTOH
    1993 Volume 30 Pages 81-89
    Published: November 29, 1993
    Released: March 17, 2010
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    Vertical distribution changes of water quality (pH, Conductivity and turbidity) in snowpack were investigated at the area of Mt. Gassan in Yamagata prefecture. Snowpack-melting water samples were collected at two different points from January to May in 1993. Ion concentration of new snow was above 50μS/cm and it was decreasing with changes of snow type from compacted snow to granular one. Profile of pH and Conductivity (EC) in snowpack had many peaks because of the difference of snow type, existence of ice layers and colored layers. High pH layer with high concentration of turbidity was observed in snowpack, and it contained rich concentration of Ca2+. Its yellow color and high concentration of Ca2+ indicated that turbid substance was Kosa aerozol (Yellow sand dust), and increase of pH was attributed to dissolution of Ca2+. Black pollutants were appeared at March investigation on the surface of snowpack and it seemed that main source of supply was stem and branch of trees.
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  • Katsuhiko MIZUNO, Harukuni TACHIBANA, Norihito TAMBO
    1993 Volume 30 Pages 91-99
    Published: November 29, 1993
    Released: March 17, 2010
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    The chemical forms and the run-off characteristics of particulate heavy metals were researched. Before the chemical analysis, the suspended matters contained in water were separated by continuous centrifuge, then the various types of heavy metals were fractionated into 5 groups from them by various solvents. Together with the data of examining the chemical components in water and mud, the followings were found out:(1) The ratio of natural mineral heavy metals becomes high in flood time, (2) Cu originate from human activities because of the close relation with organic matters, (3) Much of Mn and Zn have a similar behavior, and they originate from industries and households. Though the amount of heavy metals in suspended solid in studied area is not so much, run-off control of suspended solids by consolidating drainage system is available for improving water circumstances.
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  • Akira SAKAI, Masaro HIRAI, Sheng Ping ZHANG
    1993 Volume 30 Pages 101-110
    Published: November 29, 1993
    Released: March 17, 2010
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    It has been recognized that nonpoint source is an impotant element to improve water quality conditins. To discuss the comprehensive management policy of water pollution control including nonpoint source, it is needed to quantify nonpoint source and understand its runoff mechanisms.
    In this study, we shall construct a model including restoring and runoff processes of point and nonpoint sources, and apply it to analyze differences of pollutants load behaviers between combined and separated sewer systems for wet weather and dry weather.
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  • Masatoshi MATSUKAWA, Hiroake SAMPA, Kenji NAGANO
    1993 Volume 30 Pages 111-120
    Published: November 29, 1993
    Released: March 17, 2010
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    Regarding the effective use of sewage sludge ash, the lime-added sludge ash, which generates from dewatered sludge using lime, is suitable as a soil conditioner because of the hardening action of calcium oxide. However, it has been considered that the polymer-added sludge ash, which generates from dewatered sludge employing polymer coagulant, cannot apply a soil conditioner because of its low content of calcium oxide.
    We tested the mixture of these two types of sludge ashes as a soil conditioning additive. The experiment indicated that this additive improved the consistency, the compaction dry density and the CBR value of the weak-strength soil. High abitity on water retention of polymer-added sludge ash and the synergic effect of both ashes couses this increase of soil strength. This result confirms the applicability of polymer-added sludge ash as a soil conditioner, thereby expanding the prospect for wider use of sewage sludge ashes.
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  • Tadahiro MURAKAMI, Tsunekazu FUKUI, Atsuhiro KIMURA
    1993 Volume 30 Pages 121-132
    Published: November 29, 1993
    Released: March 17, 2010
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    Behavior of ash components of sludge in coke-bed sludge melting furnace was examined at commercial plants with capacities of 10 t-DS/day and 40 t-DS/day. Sludge fed to furnace is dried and decomposed by high temperature gas blowing up from burning coke-bed. Ash components of the sludge are molten in the coke-bed with a temperature over 1500°C, and molten slag flows out from the furnace. Retention time of ash was measured using titanium and manganese added to the fed sludge as tracers. Effects of tracers appeared at ten to fifteen minutes after feeding tracers and peaks of concentration in slag were observed at fourteen to thirty four minutes after feeding. Average retention time was twenty nine minutes. Slag recovery rate varied from 70% to 90%. Testing method to measure ash defines to heat at 600°C, but temperature higher than 1200°C is required to melt ash. Heating test was carried with different kinds of sludge. Heating from 600°C to 1200°C, weight reduction of 26-40% was measured, but reduction rate was depended on the kind of sludge. Weight reduction was big when heating up to 815°C, and reduction at a temperature over 815°C was depended on the type of sludge. Main materials causing weight reduction were unburnt carbon (C) and some other elements like sulfur (S), chlorine (Cl), some metals like sodium (Na), potassium (K) and oxygen (O) released from some kinds of oxide. Even though very small quantity, zinc (Zn) and lead (Pb) were also vaporized.
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  • Kouji MORINAGA, Teruyuki UMITA, Tatsuo OMURA, Jiro AIZAWA
    1993 Volume 30 Pages 133-142
    Published: November 29, 1993
    Released: March 17, 2010
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    Removals of heavy metals from digested sewage sludge such as Cu, Cd, Ni, Zn, Mn, Pb and Cr were investigated by the batch experiments in addition of Thiobacillus ferrooxidans and ferric sulfate.
    The addition of T.ferrooxidans to the sludge brought favourable effects for the elution of heavy metals from the sludge, especially for Cu and Cd. The elution of heavy metals was also stimulated by the addition of ferric sulfate which would be indirectly converted into the substrate for the bacterial growth in the elution process of heavy metals.
    The major form of heavy metals lost in the sludge after the experiment was the form extractedfrom the sludge by 1M HNO3. This form of heavy metals was easily removed from sludge by T.ferrooxidans. The major form of Zn and Mn in the sludge before the experiment was the form extracted by 0.1M Na4P2O7, which was also eluted by the addition of ferric sulfate.
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  • Shinsuke MORISAWA, Yoriteru INOUE, Masaru TANAKA
    1993 Volume 30 Pages 143-151
    Published: November 29, 1993
    Released: March 17, 2010
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    Probability technique for estimation of contaminant leakage points was combined with the numerical simulation technique for contaminant transportaion in the ground, to develop practical procedures for identifying the leakage point at a hypothetical municipal solid waste landfill site. The procedures were applied on the optimum monitoring wells system, which was allocated in advance of the landfill operation, to illustrate how to identify the leakage points using the additinal monitoring information after the landfill operation.
    The results obtained under the limits considered can be summarized as follows;
    (1) The framework to allocate additional monitoring wells for identification of contaminant leakage points can be mathematically described as the problem to find the numbers of wells and their locations which show the least expectation of an entropy of the conditional probability for identification of leakage points.
    (2) The entropy of the conditional probability can be used as the index which shows how certain the identification of leakage points is. The less entropy shows the more certain identification. Zero entropy means ideal identification.
    (3) Example allocations of additional monitoring wells were illustrated using possible set of monitoring information.
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  • Hai Nan KONG, Yuhei INAMORI, Hiroshi NAKANISHI, Ryuichi SUDO
    1993 Volume 30 Pages 153-163
    Published: November 29, 1993
    Released: March 17, 2010
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    This study dealt with treatment efficiency, granulation property, property of bacteria and activity denitrification of circulating process, which consisted of self granulation process and aerobic biofilter filled with ceramics, under high loading of 5.25kgTOC.m-3·day-1, 0.94kgT-N. m-3·day-1 (HRT6. 2h) for two years. The results obtained from this study were as follows:
    (1) Stable treatment characteristics were observed and removal rates of TOC and T-N were nearly 97% and 70% respectively.(2) Compared with non-circulation process, the MLVSS of granule was higher in this process, and the average diameter of granule was bigger, and granulation property maintained in two years.(3) Stable treatment was performed when the loading fluctuation was changed within ±20%, however, when the loading fluctuation reached to ±40%, granulation property was effected and removal rates became lower.(4) When the operation temperature rose from 20°C to 30°C, the granulation property became better and removal rates became higher, on the contrary, when the operation temperature fell down to 10°C, the granule floated out and the removal rates of TOC and T-N became lower greatly.(5) The number and activity of denitrifying bacteria per unit volume of self granulation reactor were 20 and 40 times higher than those in Anoxicioxic·Activated Sludge Process.
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  • Bao Gang Liu, Tadahiro Mori
    1993 Volume 30 Pages 165-174
    Published: November 29, 1993
    Released: March 17, 2010
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    Thermophilic Oxic Process was applied to treat the “shochu” processed wastewater which contained extremely high Biochemical Oxygen Demand (BOD) and Suspended Solids (SS). The optimum operational conditions such as BOD load, aeration rate, etc. were investigated. It was found that the BOD and Total Organic Carbon (TOC) removal efficiencies were 100% and a minute amount of excess sludge was formed when the BOD load was 6 kg·m-3·d-1 and aeration rate was 300l·m-3·min-1. The carbon balance showed that almost all of the input carbon was converted to carbon dioxide (CO2). The water and thermal balances demonstrated that all of the added water was evaporated; 66% and 34% of it were evaporated by the heat of biological reaction and electric heater, respectively.
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  • Masami TAKEUCHI, Sadaaki MURAKAMI, Masayuki FUKAGAWA, Hiroshi NAKANISH ...
    1993 Volume 30 Pages 175-186
    Published: November 29, 1993
    Released: March 17, 2010
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    Photographic wastewater bears high level of various organic and inorganic chemicals which can not be deducted to the extent permitted for disposal only with a biological or a chemical method. We had proposed a three-stage treatment system; the wastewater is treated biologically at first, then chemically to reform the remaining refractory chemicals biodegradable, and biologically again. High cost of chemical stage is reducted by minimizing the treatment time enough to reform chemicals. In this study, ozone was applied to the chemical stage and the removal efficiency of the system has been discussed.
    Ozonation of photographic wastewater, which had been treated biologically, enhanced BOD of the wastewater. Typical refractory chemicals used in photographic processing were ozonated and it was found that their BOD was enhanced enormously. The absorbance by the wastewater at 310nm was disappeared when its BOD was reached maximum. The optimum ozonation time can be determined with a monitor of absorbance at 310nm.
    The 1st biological-ozonation-2nd biological process removed 96% of COD; the contributions to COD removal were 64%, 17% and 15% for 1st biological, ozonation and 2nd biological stages, respectively. The process removed 99% KjN; 26%, 2% and 71% for 1st biol., ozonation and 2nd biol. stages. 46% of TN was removed and N remained as NO3-. The basic process for COD removal from photographic wastewater is thought to be established, but the additional N removal process is necessary to discharge the treated water into the N regulated waterbody.
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  • Tatsuo SHIMIZU, Norihito TAMBO, Kenzo KUDO, Akira NAKABAYASHI, Toshio ...
    1993 Volume 30 Pages 187-196
    Published: November 29, 1993
    Released: March 17, 2010
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    An anaerobic fluidized bed (AFB) bioreactor followed by an aerobic bioprocess enables effectively simultaneous removal of suspended solids, organic matter, phosphorus and nitrogen compounds. In the AFB bioreactor, suspended solids, colloidal matter and phosphorus were coagulated with the combined use of small amount of polymerized aluminium chloride and weakly anionic polymers to generate large sized coagulated sludge which could rapidly separate from the liquid. Especially, in the summer season with high water temperature, the pelletized sludge with high effective density can be produced. The microscopic observation showed the pelletization of sewage pollutants was caused by chemical coagulation as well as bacterial growth. Above 18°C of temperature, recycling of nitrified effluent from the aerobic bioprocess to the AFBbioreactor achieved complete denitrificationandnitrificationwitha total retention time of 4h (2h in AFB bioreactor and 2h in the aerobic bioprocess) and a recirculation rate 3 times the feed rate, resulting in above 80% of total nitrogen removal efficiency.
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  • Akiyoshi OHASHI, Hideki HARADA, Kiyoshi MOMONOI, Takeshi KUROKAWA
    1993 Volume 30 Pages 197-208
    Published: November 29, 1993
    Released: March 17, 2010
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    A geometric model is proposed herein to quantify relationship between diffusion coefficient within biofilm and dry density of biofilm. This model describes a tortuosity structure of porosity in biofilm consisting of either bacillary cells or spherical cells. Nitrite diffusion coefficients in seven kinds of particles layers, which consisted of glass beads or vinylon fibers, were measured for verification of the model proposed. The results of the experiment gave good agreement with the theoretical values estimated by the model. The diffusion coefficient in the particles layers estimated from the model was affected neither by particle size nor by the difference in shape between spherical and bacillary at a porosity above about 0.3. The model predicts that diffusion coefficient within biofilm decreases with increasing biofilm density, leading to about 80% of that in water when the dry density is 25g·l-1.
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  • Tsuyoshi IMAI, Tetsuya KUSUDA, Hiroaki FURUMAI
    1993 Volume 30 Pages 209-217
    Published: November 29, 1993
    Released: March 17, 2010
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    The objectives in this study are to develop a layered model with attrition for the growth process of biofilm in a methanogenic fluidized bed reactor, to discuss the possibility of existence of “dormant” biomass in the biofilm, and to estimate distributions of active biomass in the biofilm by the model. The model expresses characteristics and distributions of microorganisms inside the biofilm. Each substrate consumption activity of attached, sloughed, and remaining biomasses is measured by batch experiments. Comparing their specific activities, the possibility of existence of “dormant” biomass in the biofilm is indicated. Dormant biomass is inactive in the biofilm, but its activity recovers by the supply of substrates. Based on results of the experiments, a layered biofilm model is developed, into which the concept of “dormant” biomass is incorporated. The accumulation process of active and dormant biomasses in the biofilm is expressed by simulation with this newly developed model.
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  • Sadahiko ITOH, Hitoshi MURAKAMI
    1993 Volume 30 Pages 219-226
    Published: November 29, 1993
    Released: March 17, 2010
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    Effect of hydrolysis on mutagenic activity of chlorinated water was investigated. Chromosomal aberration test using Chinese hamster lung (CHL) cell was carried out to evaluate mutagenic activity. It was found that activity-induced chromosomal aberrations of chlorinated humic acids solution decreased with hydrolysis reaction. The observed hydrolysis rate constant at neutral condition (pH7.1), 20°C was determined to be 1.76 day-1, and half-life was estimated to be 9.5 hours. While chloroform was produced with hydrolysis reaction, activity-induced chromosomal aberrations decreased. Activity-induced chromosomal aberrations of chlorinated water could be attributed to chlorinated and/or oxidized by-products excluding chloroform. Effects of hydrolysis reactions of 1, 3-dichloro-2-propanono and 1, 1, 1-trichloropropanone. which were mutagens identified in chlorinated waters, were examined. It was found that the decreases of mutagenic activities of these mutagens proceeded by cleavage of chlorine by hydroxide ion, suggesting that the same mechanism existed in hydrolysis reactions of chlorinated drinking waters and chlorinated effluents from sewage treatment plants.
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  • TOMONARI MATSUDA, TAKASHI YAGI, HIRAKU TAKEBE, SABURO MATSUI
    1993 Volume 30 Pages 227-234
    Published: November 29, 1993
    Released: March 17, 2010
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    FADU (Fluorometric Analysis of DNA Unwinding) is one of the most simple and sensitive methods to detect DNA strand breaks. We tried to apply this method as a short-term test which detects DNA-damaging environmental agents. An SV40-transformed human fibroblast cell line WI38-VA13 was used, and the oliginal FADU protocol was modified in this study. DNA strand breaks induced by physical and chemical carcinogens such as γ-rays, ultraviolet light, MNNG, 4NQO were detected efficiently by using the modified protocol. We also tried to detect DNA strand breaks caused by the effluent of a waste water treatment plant. About 5.6 strand breaks per 108 base pairs were induced when cells were exposed for 1 hr to water sample which was concentrated 200 fold. This represents DNA damages equivalent to approximately 11.2 strand breaks per average human chromosome. We conclude that the FADU assay using VA13 human fibrobrast cells is useful for detecting DNA damaging substances in the environmental water.
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  • Noriaki SEMBA, Takashi KONNO, Hidetaka TAKIGAMI, Saburo MATSUI
    1993 Volume 30 Pages 235-242
    Published: November 29, 1993
    Released: March 17, 2010
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    The Bacillus subtilis rec-assay which can detect DNA toxicity was applied to water samples from various points and non-point sources.
    In the application of the assay, there are technical problems such as a concentration method of DNA toxic substances. In general, there is a close relationship between biological concentration factor and Pow (Octanol-water Partition Coefficient). Hydrophobic chemicals whose value of Pow is high, have more significant effects in ecological toxicity including DNA toxicity. This means that the selection of concentration methods of DNA toxic substances in water, should focus on better capacity of absorption of hydrophobic substances. Four kinds of resins, XAD-2, XAD-4, Blue-rayon and Sep-Pak Plus C18 were examined in the capacity of absorbing hydrophobic chemicals. XAD-2 and XAD-4 resins were found to be better among the four.
    The application of the assay using XAD-2 resin was conducted for the samples of municipal sewage, primary treatment effluent, secondary treatment effluent, night soil treatment effluent, rain water and run-off water. We could detect DNA toxicity in all the samples, which means DNA toxic pollution extended widely in our environment.
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  • M. AKIBA, T. KITSUDA, S. NODA, M. NAKAMURA, T. MORI, T. SATO
    1993 Volume 30 Pages 243-249
    Published: November 29, 1993
    Released: March 17, 2010
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    Suspended sediment accumulation in dredged sites of brackish Lake Nakanoumi has caused problems such as the release of nutrients and the generation of hydrogen sulfide. It is of great importance to know the characteristics of the suspended sediments at the dredged sites in order to control these problems. The characteristics of the suspended sediments at the dredged sites are; water content, 700%; ignition loss, 22%; Eh, -170mV; and average grain size, 10μm. By comperison, the characteristics of the suspended sediments away from the dredged site are; water content. 350%; ignition loss, 16%; Eh, +20mV; and average grain size, 20μm. Several kinds of diatoms were found in the suspended sediments at the dredged sites, the dominant species being Skeletonema sp. which frequently appears in the “red tide” of Lake Nakanoumi. Many mineral particles (mainly quartz) were found in the suspended sediments away from the dedged sites.
    From these results, it was found that the characteristics of the suspended sediments at dredge site were higher water content and ignition loss, lower Eh value, and smoller grain size, compared to the sediments outside the dredge sites.
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  • Kazuo TAKI
    1993 Volume 30 Pages 251-256
    Published: November 29, 1993
    Released: March 17, 2010
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    No prediction of the rate of resuspended load on mud has ever sufficiently focused on the characteristics that sediment material is small and cohesive. This paper will attempt to introduce this nonincluded factor in the prediction of critical tractive force of mud. The critical tractive force which may be termed as the so-called “theory of electrochemical anchoring force”, is calculated from the condition under which cohesive force obtained from the sum of the van der Waals' attraction between two mud particles, and the force caused by the surface charge of particles. In a region less than tens gm of particle diameter, or lager than 2 of relative water content (W/WL, WL means the liquid limit of water content), the critical tractive force decreases almost exponentially in the value of noncohesive critical shear stress as the water content increases.
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  • Makoto MATSUBARA, Haruki WATANABE, Kazuaki SATO, Atsushi KASAI
    1993 Volume 30 Pages 257-266
    Published: November 29, 1993
    Released: March 17, 2010
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    Sewage sludge pumping experiments were conducted by using a loop pipeline to establish the methods of predicting pressure drop. To avoid changing sludge viscosity during pressure measurement and to measure the viscosity exactly by the rotational viscometer, sample sludge was fully circulated and sludge particles were disintegrated to some extent before the measurement. In case of laminar flow, experimental Darcy-Weisbach's friction loss factor f was successfully expressed by Reynolds number Re for non-Newtonian fluid, such as Bingham Plastic and Pseudoplastic. The relationship between Re and f became f=64/Re like water. In case of turbulent flow, however, sludge did not have the same relationship as water except for dilute Newtonian sludge. The method proposed by Dodge and Metzner gave us a relatively good result. The applicable region of Chou's method, which has been used commonly in Japan and is based on sludge multiplication factor, turned out to be very limited. Then, we tried to improve on this method and proposed a new one to which the factor calculated with sludge concentration and average velocity was applied.
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  • N'guessan Bi Tozan Michel, H. Hozumi, H. Yoshida, H. Ueda
    1993 Volume 30 Pages 267-273
    Published: November 29, 1993
    Released: March 17, 2010
    JOURNALS FREE ACCESS
    dual-media filter with a coarse medium at the upper part and a sand bed at the lower part has been proposed for the direct filtration of secondary waste water effluent from an activated sludge treatment plant. Filtration without coagulation gave, for the model proposed, a filter run length five times that of the single sand bed filter at the rate of 120m/day. Laboratory experiments were carried out to evaluate the optimum values of pH and aluminum dosage that gave a color removal of up to 70%. Coagulant-assisted filtration without pH control gave a color removal of up to 40%. The filter performance was measured in terms of (1) filter run length and (2) removal of color, COD and phosphate.
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  • S. Takizawa, Y. Suzuki, M. Takahashi, S. Hatano, J. Miyata
    1993 Volume 30 Pages 275-286
    Published: November 29, 1993
    Released: March 17, 2010
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    A serial Nitrification-Denitirfication Process (O-AO-O Process) which utilizes organics incorporated into bacteria as the main carbon source for denitrification, has been recently developed as a nitrogen removal process from domestic wastewater. More than 80% of nitrogen can be removed from wastewater by the O-AO-O Process without nitrified-liquor recirculation, hence it can save enrgy. However, it requires comparatively long Hydraulic Retention Time (HRT), ca. 20 to 24 hours, in the biological reactors. The objective of this study is to develop a process which can cut required HRT of the present O-AO-O process by half. A 165L pilot plant was fablicated and experimental studies on nitrogen removal from domestic wastewater were carried out from June 1992 through May 1993. Polypropylene pellets were added up to 40vol.% of the oxic-tank in order to enhance nitrification, and effects of immobilizing pellet and ORP on denitrification were investigated. Whereas the water temperature in the reactors fell as low as 12.5°C, 65% of the influent nitrogen was removed within 13.2 hours of biological reaction time.
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  • K. MORIYAMA, M. TAKAHASHI, T. KITAMURA
    1993 Volume 30 Pages 287-293
    Published: November 29, 1993
    Released: March 17, 2010
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    Organic substrate in influent is utilized as an organic carbon source for denitrification reaction in most of the biological nitrogen removal process. Consequently, BOD concentration in influent is one of the most important factors for biological nitrogen removal from wastewaters. The BOD concentration can be controlled by either installing a primary clarifier or not. Therefore, a pilot plant experiment was conducted to study the effect of primary clarifier on the nitrogen removal and other treatment characteristics in the sequential nitrification-denitrification process using endogenous respiration. Two pilot plants with and without primary clarifier were operated with domestic wastewater as influent. It was shown that the efficiency of total-nitrogen removal in the plant without primary clarifier was higher than that in the plant with it. From the experimental data, it became clear that the primary sludge was a useful organic carbon source with low strength of nitrogen for denitrification reaction. It was also verified that the ammonification of organic nitrogen in influent could alleviate the alkalinity deficit in the plant without primary clarifier. As the value of autolysis coefficient of activated sludge increases with SS in influent, there is little difference between the two plants in sludge generation rate. The results of this study suggest that the necessity of primary clarifier and its capacity must be reconsidered to upgrade the nitrogen removal efficiency.
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  • Tsuyoshi HIRATA, Koki GOTOH, Nobuo USHIAMA, Atsuhisa SATOH
    1993 Volume 30 Pages 295-301
    Published: November 29, 1993
    Released: March 17, 2010
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    The pH effect of coagulation treatment on cross-flow type filtration was investigated using kaoline suspension and Alum coagulants. Flux of membrane filtration was improved under the low ALT ratio (0.001) at pH 5. Although flux of membrane filtration was increased with the increase of ALT ratio and pH, the amount of coagulant is getting large. Although sweeping effect in membrane becomes large because of the increase of floc size with increase of Alum dosage, the amount of aluminum hydroxide becomes large, so, improvement of flux is getting slow down comparing with the flux at low pH range. In the pH range from 6 to 8, the best backwashing interval for the increase of effectual filtrate is 10 min without coagulant and 30 min with coagulation treatment (ALT=0.01).
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  • GenYong Liu, Kiyoshi MOMONOI, Hideki HARADA
    1993 Volume 30 Pages 303-310
    Published: November 29, 1993
    Released: March 17, 2010
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    The effect of soluble microbial products (SMP) on permeate flux and resistances in ultrafiltration incorporated into activated sludge process was investigated. In a resistance-inseries model applied in this study, gel layer resistance was assumed to be proportional to gel layer thickness (Lg) and gel layer formation concentration (Cg), i. e. Rg=α·Lg·Cg. Resistance coefficientαand mass of gel layer Mg was used for interpretation of the influences of suspension composition and operational conditions on permeate performance. The results suggested that high molecule SMP accumulated in the reactor plays a more significant role in the decline in permeate flux rather than MLSS. It is found that permeate flux dropped logarithemically with increasing SMP concentration. The declination in flux or the increase in resistance was due to the increase in gel layer mass independent of resistance coefficient α. It is observed that applied pressure and crossflow velocity affect both cake layer resistance and gel layer resistance. As applied pressure was raised, the gel layer resistance increased correspondently. This is attributed to the same variation in resistance coefficient as gel layer resistance. On the other hand, gel layer resistance decreased with crossflow velocity due to decrement in the Mg.
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  • Koki GOTO, Yoshitsugu JIMBO
    1993 Volume 30 Pages 311-319
    Published: November 29, 1993
    Released: March 17, 2010
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    Membrane filtration of ground water, which included high concentration of Fe, Mn and dissolved-SiO2, was investigated using 5 kinds of membrane. In the case of air oxidation, particle size of oxide was 0.03-0.1μm, and its coagulation state was poor. So, perfect removal of Fe by MF membrane was difficult without Alum dose.
    In the case of chlorine oxidation, particle size of oxide was 0.01-0.03μm, and the removal of Fe by membrane (pore size below 0.1μm) is perfect because of high coagulation state of oxide. The removal of Mn by MF and UF membrane after chlorine oxidation was 80-90% but concentration of Mn was not below 0.01mg/l. The concentration of Mn by the combination of Mn-sand filtration after membrane filtration reaches below 0.01mg/l. The increase of filtration resistance of UF and MF membrane depends on the pore size and the coagulation state of oxide by the difference of oxidation method.
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  • Chunmo ZHU, Hegze SHEN, Masao UKITA, Hiroshi NAKANISHI
    1993 Volume 30 Pages 321-327
    Published: November 29, 1993
    Released: March 17, 2010
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    This paper discussed the water quality, water quality model and natural purification capacity as well as their seasonal characteristics in Tumenjiang River, flowing through China, North Korea and Russia into Japan Sea. Following conclusions were obtained:
    1. There were found good correlations between CODcr, BOD5 and CODMn in the river water polluted by the wastewater from the pulp and paper mill.
    2. The water quality model applicable to the mid-reaches of the River was introduced, including seasonal change of the natural purification capacity.
    3. By utilizing the purification capacity efficiently, it was recommended to construct a stock lagoon and to store a part of the wastewater in winter, low-water season and discharge it in the period of high-water. The treatment cost required for this process was estimated to be 46 Chinese yuan (930yen)/ton pulp, and 209 Chinese yuan/t·p will be saved than that for the wastewater treatment of 60% cut corresponding to the present standared in China.
    This study will be useful to “Tumenjiang Development Project” organized by UNDP.
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  • Kazuhisa FUKUNAGA, Yukio HAGA, Keisuke OJIMA, Morio SAKATA
    1993 Volume 30 Pages 329-340
    Published: November 29, 1993
    Released: March 17, 2010
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    As a method of improving water quality in enclosed coastal seas, the gravel contact method is highlighted. Recently, this method has been applied to the purification of river water, still more the study of coastal water treatment by the gravel contact method is going to be at an early stage. To compare with river water treatment, coastal water treatment is extremery difficult because of existence of attached organism and filter feeder. Although these filter feeders have an adverse affect on the apparatus, they can also be expected to have an effect on purification. In this paper, the purification rate was calculated from the pilot plant test data. COD purification rate and oxygen utilization rate were expressed as a function of water depth. And they were compared to total purification rate and total oxygen utilization rate including the effects of microorganisms.
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  • Ying An, Tatuo OMURA, Teruyuki UMITA, Jiro AIZAWA, Yoshimitu SATO
    1993 Volume 30 Pages 341-350
    Published: November 29, 1993
    Released: March 17, 2010
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    The seasonal variations of biological water quality indices based on benthic animals were investigated in the Ohkawa river which was flowing through the agricaltural area. The water quality of Ohkawa river was characterized by comparatively low organic pollution and high concentrations of nutrients such as nitrogen and phosphorus.
    The total number of species of benthic animals which appeared in the Oh-kawa river through a year was 132 species, and most of species appeared were belonging to Ephemeropter, Trichoptera and Diptera.
    The seasonal variations in both the number of species of benthic anamals and the number individuals were clearly observed.
    And also the seasonal variations of the biological indices such as similarity index (Cλ), the diversity index (DI), the tolerant species index (I) and the pollution index (PI) which were based on the benthic animals were more useful in judging the water quality in the Oh-kawa river from the biological and biochemical viewpoints.
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  • ESPECIALLY ON LITTLENECK CLAM
    Masahiko SEKINE, Masao UKITA, Hiroshi NAKANISHI, Toshiaki NARAZAKI
    1993 Volume 30 Pages 351-359
    Published: November 29, 1993
    Released: March 17, 2010
    JOURNALS FREE ACCESS
    Although there are many development activities in coastal areas, influence of such activities on ecosystem is not revealed enough. In Ajisu tidal land, wave dissipating concrete blocks were established in front of seawal. The purpose of this study is to estimate the influence of the wave dissipating concrete blocks on ecological environment of Ajisu tidal land, especially on littleneck cram which is the most important resource of fishery afound the area. Ground level, ground water leve1, current velocity, SS and Cl concentration in sea water, particle size distribution of mud, ignition loss of mud, and biomass of littleneck clam were surveyed at 126 grid points in 800m×100m area during 1991 and 1992. The results were combined and put it in cluster analysis. The area in front of the wave dissipating concrete blocks were clusterized in one special cluster. The results are; In normal weather condition, wave dissipating concrete blocks worked positive to clam because they promoted the settlement of juvenile shell and its feed. In abnomal weather condition such as typhoon, wave dissipating concrete blocks worked negative to clam because they scattered sand which accumulated during normal weather period and might caused death of clam by burying them.
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  • Toshihiro KITADA, Chiharu YONEZU
    1993 Volume 30 Pages 361-370
    Published: November 29, 1993
    Released: March 17, 2010
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    Urbanization in coastal area possibly changes climate in inland area through local flow systems such as sea breeze. In the Nohbi plain, which is located on the Pacific ocean side, central Japan, the coastal urban area having expanded during a decade from 1975 to 1985 raised daily-maximum temperature over its inland suburbs on summer sunny days; this was partly attributed to horizontal heat transport by the sea breeze warmed up over the coastal urban area. In this paper, results of hypothetical sensitivity study using numerical heat transport simulation, are reported on the mitigation of this inland high-temperature by changing land use over the coastal urban area, namely, by increasing area-ratios of forest and environmental open water there. The principal conclusions are:(1) the forest and open water introduced in the coastal urban area can decrease the maximum temperatures over a large inland area, (2) the temperature decrease ranged from 0.3°C to 2.0°C depending on the type and the extent of the land-use newly introduced; this decrease was almost equivalent to that calculated for the “without artificialenergy-use” case, and (3) these reduced temperatures of background air mass are expected to contribute largely to saving energy for air-conditioning in the regional scale in summer time.
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  • Toshiaki ICHINOSE, Keisuke HANAKI, Tomonori MATSUO
    1993 Volume 30 Pages 371-381
    Published: November 29, 1993
    Released: March 17, 2010
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    Concerning the energy consumption structure in urban areas, cities in several countries were analyzed by unified standard and their characteristics were compared and discussed. Analysis by published statistics clarified the characteristics of the energy consumption in each sector or type of fuel in each city. The difficulty in the comparison of unit energy consumption based on economical indices was noticed. The urbanization increases the energy consumption in developing countries, while it decreases it in developed countries, according to the difference of the life style between urban and rural area.
    Additionally, the relationships between the heating degree month and the unit energy consumption in the household sector was compared between China and Japan. The difference of impact for human activity by the global warming between both countries were clarified.
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