Most of algae which affect the filter clogging in water purification process for drinking water are slender type diatom. In this study, the filtration experiment has been performed using the practical slender diatoms to clear the mechanism of deposit in the filter. The ratio of filter grain size to the length of slender type diatom is closely related with the filter efficiency, the headloss profile in filter layer. As the results, it is indicated as follows: 1) the efficiency of filtration is higher comparatively under the filtration of filter grain size, d within about 15 times of length of slender type diatom, s, but it decreases with ratio of grain size to length of diatom, 2) on the penetration depth, which is correspond to the filter depth of the 95% headloss appearance to total headloss for the deposit in the filter, of diatoms into sand filter layer, under the condition such less than 15 in ratio, d/s, the number of thin filter layer having depth of grain size for the penetration depth is within about 50 only.

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A modified jar-test method, comprising a rapid mixing process with a time of 5 minutes and a filtration process with glass fiber filters or membrane filters, was used to evaluate the quality of filtered water in direct sand filtration of surface water with low turbidity and relatively high color content. The results showed that with the application of this method, the time needed for evaluating the quality of filtered water in direct sand filtration was greatly shortened (of several minutes), compared to about one hour with the conventional jar-test method. Furthermore, the estimation of the efficiency of several different types of coagulants in direct sand filtration by the modified jar-test method made clear that PACI (Poly-aluminum chloride) was more effective than alum, and the cationic polymer performed much better than either the nonionic or the anionic polymer.

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The effect of soluble microbial products (SMP) accumulated in reactor on permeate flux and formation of fouling layer was investigated. In a continuous treatment of synthetic wastewater by activated sludge process incorporated with ultrafiltration membrane, it is known that permeate flux was dropped with an increase in SMP concentration, due to an increase in fouling mass adhered onto the membrane surface. From the result of SMP influence on bacterial adhesion to various membranes and coating surfaces by SMP, it was found that bacterial number per unit area was in proportion to the SMP concentration in bulk suspension. Bacterial adhesion number is influenced by the surface tension of substrates used in adhesion experiment. Coating membranes surface with SMP caused an increase in bacterial adhesion number, as the result of an decrease in membrane surface tension. From the thermodynamic model for the adhesion of bacteria from a suspension onto the membrane, it was found that the variation in bacterial adhesion number correlated well with the thermodynamic predictions. These results indicated that SMP accumulated in reactor promotes bacterial adhesion to membrane or fouling layer surface. Influence of SMP on the permeate flux drop could be considered as the promoting effect of SMP on bacterial adhesion, as well as SMP direct adsorption to membrane surface.

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To investigate the fouling process and mechanism of OF membrane due to organic colored matter, continous experiments were carried out. Ceramic membrane (CM 20, 000, 150, 000 Dalton) and cellulose acetate membrane (CA 100, 000 Dalton) were tested for a diluted kraft pulp black liquor. The increase of transmembrane pressure difference of CM was higher than that of CA. The increase was mainly affected by setting flux and feed concentration. Shorter interval and longer time of back washing was effective for decreasing the pressure difference. Some decrease of the pressure difference was also observed after stoppage of electric current. After an initial period in which little removal was shown, especially in CM 150, 000, effective removal was revealed in accordance with an increase of the pressure, with more removal being achieved for higher feed concentration. Thus, the removal of colored matter would depend upon a growth of fouling on a membrane surface. SEM observation showed a tight gel layer of colored matter, which could not be easily detached by back washing. The layer on CA membrane, however, had many cracks and traces of back washing, which would be formed by some vibration and contraction of membrane elements during back washing. This would be because that the pressure difference of CA did not increase rapidly. After HPLC analysis, the molecular weight of colored matter retained in a gel layer was estimated to be in the order of 10³ Dalton.

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Low pressure reverse osmosis (LPRO) is an effective wastewater treatment process providing high permeation of water and high rejection of solutes. The LPRO experiments were made with inorganic solutions of Na⁺, Ca²⁺, Mg²⁺ and Cl^- and organic matters in different concentrations and pH levels. The experimental results showed that the solute permeability in LPRO membrane depends on the charge of membrane and ions in many cases. The divalent cations provided lower rejection of coexistent cations in mixed solutions system than that of the cation in single solution system. The LPRO was very effective in removing inorganic matters and organic matters in artificial incineration ash leachate. The membrane permeations of inorganic ions in the leachate were similar to those in mixed solutions system.

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The groundwater which contained iron, manganese and disolved silica in high concentrations, was oxidized to be deposited under the presence of manganese dioxide. It was filtered through two types of UF membranes and an MF membrane at a membrane filtration flux of 1-3m/d. The change of transmembrane pressure difference and the quality of the filtrate were investigated. After the continuous filtration experiment, the chemical cleaning effect was investigated. It is considered that the slower membrane filtration flux gives larger quantity of filtrate. When the membrane filtration flux decreases to a certain level, the effect of the membrane filtration flux becomes insignificant. The UF membrane having a smaller moleculer weight cutoff will suppress the increase of transmembrane pressure difference after a long period of operation. If the detention time is 30 minutes or more, the concentration of manganese dioxide becomes a factor rather than the detention time of the reaction tank. In chemical cleaning, the flux of UF membrane is almost perfectly recovered by acid cleaning, but the flux of MF membrane shows a poor recovery. A presumable cause of MF membrane is the direct invasion of manganese beneath the membrane.

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Removal efficiency of organic matters was investigated using a hybrid membrane systems combined with a nano filtration system and an activated carbon process. The surface water of Chitose river which contains relatively high concentratoin of organic matters (i.e. humic substances) was treated. The results of this study indicated that pre-coagulation process did not improve the removal efficiency of organic matters. The removal efficiency of dissolved organic matters by the activated carbon process gradually decreased to only 30% and reached an equiliburium condition, while that of the NF system was always over 90%. Although manganese could not be sufficiently removed by even the NF process and/or any combinations of these processs, applying chlorination before the MF process promoted the complete removal.

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The objectives of this research were to investigate the feasibility of direct filtration (DF) of raw sewage, and decomposition of captured organic matters by thermophilic oxic process (TOP). Feasibility of this process was assessed by determining removal efficiencies of SS, BOD, and the change in particle size distribution when filtration rates are changed. Wood chips of which size is 10mm was used as media both for direct filtration and thermophilic oxic process. When the filtration rate ranged from 100-220m·d^-1, removal efficiencies of SS and BOD by the filtration were 70-80% and 40-50%, respectively. Approximately 70-80% of captured BOD was decomposed by TOP with the aeration rate of 100 1·m^-3·min^-1 and BOD load of 3.0kg·m^-3·d^-1. The media can be reused both for filtration and thermophilic oxic process without backwash

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It is necessary to make high quality compost in order to expand the utilization of biosolid produced in sewage treatment plants. The high quality compost should not only possesses characteristics of ordinary compost, but also has superior ability to improve soil properties and contains more plant nutrients. Additives, which were possessed of two functions, were used in this research. One is called bulking material function that contributes to adjusting moisture content and improving the permeability of air during the active composting. The other is called soil amendment function that contributes to improving soil properties and to balancing plant nutrients. Cedar chips, zeolite, charcoal and rice bran were used in this study. The results indicate that cedar chips are the suitable bulking material because it possesses large water adsorption capacity and low bulk density. Zeolite not only has high ability of NH3 adsorption but also possesses large value of cation exchange capacity (CEC). Charcoal functions as soil amendment. Rice bran contains a fairly high amount of plant nutrients. The compost in which cedar chips, zeolite, charcoal and rice bran are added contains high ability of improving soil property and fairly amounts of plant nutrients. Using these materials as the additives, the high quality compost was produced.

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A new treatment process involving yeast utilization was developed to treat potent wastewater from a dried food products factory. Using wastewater, three yeast strains were isolated from an enrichment culture. The first treatment facility, seeded with the mixture of the isolated yeasts, was installed at the dried food products factory in 1989. After four years, the treatment performance was investigated for a year. The yeast treatment process was able to remove over 95% of BOD even when operating under extremely high loads of 16kg BOD·m^-3·d^-1, and responded to a load variation of 5-16kg BOD·m^-3·d^-1. Moreover, this process could decompose the suspended solids and reduce both air supply and sludge yield. On the other hand, the limitations of yeast treatment lay in terms of the quality of treated water. About 120mgl^-1 of BOD always remained in the yeast treated water, and nitrogen and phosphorus could not be removed except for the amounts required for yeast cell synthesis. However, the quality of effluent could be improved by combining the yeast treatment and bacterial treatment processes.

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The structure of biofilm is composed of two parts, base and surface films. In the region of base film, molecular diffusion is considered to be distinguishable. On the other hand, the behavior of surface film is influenced by the mechanical behavior of fluid on surface film and by the configuration of the surface of the biofilm. The change in surface roughness of the biofilm formed by acidophilic iron-oxidizing bacteria and iron precipitates and the effects of the surface roughness on substrate removal flux were investigated by continuous and batch experiments. The ratio of profile length to the length of substratum and rms (root mean square) and power spectrum was used as the quantitative index of surface roughness. The two-dimensional simplified biofilm model in which the roughness of surface was apporoximated to the continuous arcs of circles was simulated by finite element method. The simulation indicated that the increased rate of flux of biofilm with rough surface increased as rms increased and approached the increased rate of surface area when rms was large. The evaluation by the si mulation showed the same trend as experimental results qualitatively.

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The factors influencing the activities of extracellular enzymes {lignin peroxidase (LiP) and manganese peroxidase (MnP)} synthesized by white rot fungus, Phanerochaete chrysosporium, were investigated by batch culture experiments. Veratryl alcohol produced as a secondary metabolite from glucose was found to be the most important substrate enhancing LiP activity. Tween 80 (a surface active agent) was considered to play an important role in LiP secretion. The LiP activity was maximal under the nitrogen sufficient condition as a response to carbon starvation, compared with the activities under both conditions of the nitrogen limited and nitrogen excess. The MnP activity was highest under nitrogen limited condition and decreased with an increase of initial NH₄⁺-N concentration. The decolorization rate of azo dye (Reactive Red 22) by Phanerochaete chrysosporium, in the presence of both LiP and MnP activities under carbon limited condition, was greater than that in the presence of MnP under nitrogen limited condition. The azo dye was also decolorized by the crude enzyme mixture of LiP.

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The dehalogenation of herbicide degradative microorganisms and its crude extracts were demonstrated from the standpoint of improving biological wastewater treatments by biochemical and genetic methods. Herbicides utilizing bacteria were screened in a medium containing 2, 4-D (2, 4-Dichlorophenoxyacetic acid) or MCPA (2-Methyl-4-Chlorophenoxyacetic acid) as a sole carbon source, one and three kinds of bacteria were isolated respectively and chloride ions were released in mediums. The resting cells of 2, 4-D degradative bacteria catalyzed the dehalogenation of 2, 4-D, 2, 4-DP (2, 4-Dichlorophenol) and 2-CPA (2- Chloropropionic acid), and the crude enzyme obtained from the cells also acted on 2-CPA, but did not dehalogenated 2, 4-D either 2, 4-DP. Activity staining of 2-CPA dehalogenase in polyacrylamide gel and its visualization were carried out to check isozymes. Single spot was formed and it led to the conclusion that only one 2-CPA dehalogenase was produced.

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Biological expanded-bed GAC (granular activated carbon) reactor was applied to treat artificial wastewater which contains high concentration of pentachlorophenol (PCP) as well as acetic acid. Organic loading was changed from 0.64 to 11g CODcr/(kg GAC·Eday) by changing concentration of organics (PCP concentration from 100 to 800mg/L and acetic acid from 500 to 2000mg/L) and hydraulic retention time from 2.2 to 0.43 days based on expanded-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 PCP removal efficiencies were kept more than 95% and 99% respectively. Biomass in the reactor was from 0.10 to 0.22mgDNA/gGAC, which corresponds to 1700-3900mgVSS/L based on the expanded-bed volume.

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In this paper, an oscillatory behavior of optimal solutions of an advanced water supply system is examined. The system has a buffer reservoir for raw water as well as a biological treatment unit and an activated carbon treatment one as advanced treatment facilities to fill a qualitative and quantitative demand of supply water in the case of drought. For the optimal design of the system, a formulation and a solution procedure have been given in our former paper. Here, for changing values of supply water quality, fluctuation with sharp increase and decrease behavior of the corresponding optimal contact length of the biological treatment unit is discovered. The optimal solutions are scrutinized to reveal the reason of the oscillation is the relation of trade-off between the design parameters of the two advanced treatment facilities of the system. This means the design procedure shown in the former paper is indispensable for the optimal design of the system.

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This paper presents a system that identifies any hyetograph as 25 representative rainfalls (Raintypes) using Fuzzy inference. The preparation of identification is consisted of two parts.(1) We define Fuzzy sets of Rainfall Volume, Rainfall Duration, Peak Duration and Peak duration for each Raintype.(2) We calculate the value of indexes (RV, RD, PI and PD) of input hyetograph using filters. We calculate the integrated membership grade for a Raintype by letting these values of indexes substitute into the membership functions of the four fuzzy sets of the Raintype respectively to get the membership grade for the four fuzzy sets and linear-connecting these membership grades. Concerning the coefficients of linear-connection, we change them according to the characteristics of input-hyetograph. We repeat the above calculation for all Raintypes. The Raintype of the biggest integrated membership grade for Raintype is defined as the Raintype to which the input hyetograph belongs. We tested this system with real rainfalls in a French local authority and get positive results.

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In recent years, many policies on water and water quality management are proposed for various problems, such as water pollution and water shortage. To choose a most suitable policy or policy combination, we need to quantitatively evaluate these policics' effects on a river basin scale.
In the present study, the evaluation system on water management with the simulation of water and pollutant balances is constructed. In this system, the random variation of water quantity is considered and probabilistic evaluation indices are calculated. Furthermore, this system is applied to the Tone River Basin and the effects of water saving and a new reservoir are evaluated. The following results are obtained from the present evaluation;
The effects of the new reservoir, Naramata, are less than the effects of 20% reduction of intake volume at the Tone-Ohzeki and both effects are larger in the lower basin.
There is no relation between water saving in the upper basin and the stability of water use in the lower basin in the Tone River.
The effects of water saving in agricultural use are larger than water saving in industrial and domestic use.

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Runoff of dissolved organic matter (DOM) was examined during snow-melt period in MOTOKISAWA area which is a small forest catchment area located in the suburb of Sendai-city. Leachate from the litter layer and soil water at 10cm depth had always high concentrations (5.0-25.0mgC/1) of DOM during the experiment period, but in the soil deeper than 20cm, the concentrations were kept in low level in spite of changes of soil water content. The concentrations of dissolved organic carbon and the absorbance at 260nm increased rapidly in MOTOKI brook during snow-melt events. From the profile of DOM in the soil water and results of separation of snow-melt runoff hydrograph using SiO₂ as tracer, it was found that the direct runoff including organic components leaching from litter contributed to the increase of DOM concentration in the brook.

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Our previous investigation had revealed various interesting aspects on tiny air bubbles found on the Abukuma river bed. The gas composition of the tiny bubbles were 99.8% of nitrogen, and it had been concluded that the river had been undergoing self-purification process of nitrogen. For the purpose of better evaluations of the microorganism activities related with nitrogen on the river bed, field research was carried out for two months from March to April 1995. On the other hand, we carried out batch tests with bed biofilms taken from the Abukuma river in which the initial NH₄⁺- N and NO₃^--N concentration were adjusted as 10mg/l. In the tests, we found that the biofilms supplied the NH₄⁺- N and NO₃^--N when the bacterial activities were low. In this report, we revealed the relationship between bacterial activities and nitrification and denitrification rate on the river bed.

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A laboratory sediment-water microcosms experiment for three lakes were conducted over 20-d incubation period. These lakes included different types of an oligotrophic, a mesotrophic, and a dystrophic lake. Two sets of microcosms for each lake were acidified to pH=4.5 with surfulic acid and nitric acid, and one of them was treated with chloroform to suppress the biological activities. All treatments demonstrates rapid pH recovery, but the acid-neutralization capacity varied between types of lakes. Cation exchange was the main process in the oligotrophic and the mesotrophic lake, whereas the biological reduction of nitrate and sulfate was the main process in the dystrophic and the mesotrophic lake. In the microcosms treated with chloroform, the acid neutralization by the biological reduction of nitrate and sulfate was suppressed and was replaced by cation exchange.

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In order to investigate the performance of thermophilic UASB reactor and the behavior of methanogenic activities of the retained sludge, a laboratory-scale UASB reactor was operated at 55°C over 8 months by feeding with an alcohol distillery wastewater. The reactor was inoculated with granular sludge grown on a carbohydrate (fruit juice) wastewater under a mesophilic condition (35°C).
The maximum COD loading achieved was 30kgCOD/m³/d, corresponding to a HRT of 7.2h for influent strength of 9000mgCOD/l, with a COD removal efficiency of around 85%. During a period of COD loading of 30kgCOD/m³/d, propionate and acetate accumulated in the effluent up to about 300-600mgCOD/l and 100mgCOD/l, respectively. Although the settleability of the retained sludge deteriorated from the initial SVI (based on VSS) of 25ml/gVSS to 52 during the first 80 days, its value gradually improved finally to 21 due to a significant proliferation of thermophilic methanogens.
Thermophilic cultivation caused a drastic shift in temperature dependence of methanogenic activities of the retained sludge. On the day 202, acetate-and hydrogen-utilizing methanogenic activities exhibited their optimum values at 65°C, while that of propionate-fed methanogenic activity occurred at 55°C. Comparing in methanogenic activities at 55°C between the retained sludge and the seed sludge, acetate-fed activity increased finally by 4.4 times, propionate-fed activity by 4.6 times, and hydrogen-fed activity by 3.5 times. Fairly lower value of propionate-fed methanogenic activity, i. e., only 1/5 of acetate-fed activity and furthermore only 1/23 of hydrogen-fed activity, suggested that the propionate degradation is subject to be a rate-limiting step in thermophilic condition.

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Hydrogen fennentation and COD removal from a wastewater with concentrated sucrose were investigated using a special consortium of anaerobic bacteria in chemostat-type reactors at 35°C. The experiment was conducted by varying the hydraulic retention time (HRT) of the reactor from 3.0 to 24.0 hours in 7 steps. When the HRT was longer than 6.0 hours, over 99% of the influent substrate was degraded and the COD removal reached to 32-35%. As a result, the influent COD (100%) were converted into various forms, including hydrogen (10.7-13.2%), acetate (11.7-12.9%), butyrate (40.3-48.5%) and biomass (14.5-21.8%). The biogas produced was mainly composed of hydrogen (40%) and carbon dioxide (60%), and the concentrations of acetate and butyrate in effluent reached to 1500mg/l and 3300 mg/l, respectively. The Monod equation was suitable to describe the relationship between the substrate concentration and the substrate utilization rate for the hydrogen-producing consortium, and all the kinetic parameters were determined. The following stoichiometric equation was obtained for the hydrogen fennentation reaction at the HRT of 8.0 hours: surose→ 3.18H₂+ 4.68CO₂+ 0.72acetate+1.17butyrate +0.39bacterial cells (C₅H₉O₃N).

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A method to derive surface albedo from satellite measurement is developed and discussed. In this method, atmospheric correction is performed by solving the radiative transfer equation, and calibration coefficients for the satellite radiometer are determined by the measurements over two reference sites; i. e., sea surface and snow-coverd surface. The sensitivity study indicates that the calculated surface albedo is not sensitive to the assumed surface albedo values of the reference sites, but sensitive to the optical properties of atmosphere. The proposed method is tested over Sapporo and Tokyo area, using NOAA AVHRR data and surface albedo maps for snow-covered area and no snow-covered area are derived. The method is shown to be relevalent for the study of urban heat island.

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Atmospheric turbidity coefficients were calculated at five sites (Nemuro, Sapporo, Shionomisaki, Tosa-Shimizu and Ishigaki) in Japanese area from 1980 through 1992. The turbidity coefficients ranged 0.03-0.30 at Nemuro, 0.05-0.40 at Sapporo, 0.05-0.45 at Shionomisaki, 0.03-0.40 at Tosa-Shimizu and 0.03-0.40 at Ishigaki. They decreased in autumn and winter, and increased in spring. Variations of the turbidity coefficients had tendency of increase from 1957 through 1992 due to increase of human activities. In 1982-1984 and after 1992, the turbidity coefficients had the maximum due to large volcanic eruptions of Mt. El Chichon and Mt. Pinatubo, respectively.

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Local winds provide important background for atmospheric environment through transport of pollutants, heat etc. Thus, urban and regional planning are required to take these winds into account for creating better living space with energy-saving ways. By understanding the mechanism of the winds system in a particular region, we can better estimate possible influence on climate of our planning activity such as urbanization. In this study we investigated how the local flow system in Nohbi plain is affected by topography of various spatial scales, the topography ranging from local coast line to the large mountain range of the size of the Japanese Alps. Using a meso-scale meteorological model which includes k-ε model for turbulence, the development-mechanism of sea breeze system in the plain area was clarified. One of the major findings is that the local circulations of valley winds and plain-plateau winds, caused by the Japanese Alps, i. e. the largest scale topography considered, dominate flows over Nohbi plain by strongly heating air mass there during daytime, although the mountains is quite far from the plain, i. e. located more than 100km north-east to the plain.

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In this case study on Asahi River Dam reservoir, we discussed the relationship between hydraulic retention time and increase of phytoplankton, and the propagation of water quality in the reservoir to the downstream. Since the observation time includes the severe drought period, the influence of the drought on the water quality is also discussed. Obsevations were carried out from spring to late autumn in 1993 and 1994 and the Observation points are located from upstream of the reservoir to the downstream. The water quality components observed are phosphorus, nitrate, chemical oxygen demand, chlorophyll-a. The water quality in the reservoir is different from the upstream to the downstream. The chlorophyll-a increases in the reservoir, but it often descreases in the downstream in spite of the sufficient nutrients. The particulate components of COD, nitrogen and phosphorus decrease during flow down. The hydraulic retention time is a limiting factor for increase of phytoplankton in the Asahi River Dam reservoir. A retention time of at least 2 to 3 weeks is necessary for the sufficient increase of phytoplankton. This retentin time can be predicted by the growth rate of phytoplankton. The water quality in the reservoir is not affected significantly by the draught since the hydraulic retention time and pollutant loads decreased.

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There has been remarkable improvement of water pollution conditions of these days, compared to that of the nineteen-seventies. But from the view point of water usage, especially for drinking water, the eutrophication is still a major problem in rivers and lakes. One of the major reason of eutrophication to occur is the excessive loading of nutrients and organic substances to the water body by industrial wastewater and/or household discharge where sewage treatment systems are not sufficient.
The Abukuma River is a very important water resource for use such as drinking water, industrial water, waterpower generation and agriculture in Fukusima prefecture. The water quality of river has been deteriorating and resulting in problems such as water pollution, increasing eutrophication and decreasing of water clarity.
At present, the average concentration of algae flowing into the Abukuma river locality is about 28μg/l. The reason of this high algae concentration was investigated. A number of effluent samples from ponds which are situated within the river basin are regularly examined.
In this report we studied the effect of effluents from fish breeding ponds on eutrophication of the Abukuma river. We want to propose the ways to improve the water qualities and to keep good condition of the Abukuma river as water resouces.

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Wetlands in estuary areas supply an important resting and feeding place for migratory birds. The preservation of these wetlands has been focused in recent years. A simulated tidal flat system was established to evaluate the treatment characteristics of fish-pond wastewater which was rich in Chl-a, SS, COD, nitrogen and phosphorus, and was directly discharged to the wetland. The results from both batch and continuous experiments indicated that the removal of suspended substances including SS, Chl-a was quite high, and the removal of organic matter, nitrogen and phosphorus was simultaneously recognized. The removal rates of COD, TN and TP were found to be 180, 120 and 18mg/m²/day, respectively. It indicated that sandy sediments of tidal flat played an important role in purification of fish-pond wastewater. However, if the tidal flat sediments are disturbed, the purification ability such as denitrification will be dropped significantly.

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First, the level of mutagenicity of 5 commercial and 6 pure surfactants was determinated using Ames' assay. Next, in order to elucidate the effects of surfactants discharged in water environment on the level of mutagenicity in it, each of the surfactants was added to Ames' assay of 4-nitroquinoline 1-oxide (4NQO) or benzo (a) pyrene (BaP) and the change in the level of mutagenicity was investigated. No mutagenic activity was found for any surfactant in the presence or absence of rat liver homogenates (S9-Mix). In contrast, the level of 4NQO mutagenicity in the absence of S9-Mix and the the level of BaP mutagenicity in the presence of S9-Mix were increased in the presence of the surfactants. Marked increases in the level of 4NQO mutagenicity were observed in the presence of the surfactants in the order of α-sulfo-fatty acid methyl ester (α-SFE)> polyoxyethylene-n-lauryl ether (AE)> amidic fatty acid (DA)> sodium dodecylsulfate (SDS)> alkyl sulfate (AS). These increases occurred when Salmonella typhimurium (S. typhimurium TA-100) was treated simultaneously with 4NQO and AS or α-SFE, when S. typhimurium TA-100 was treated with SDS followed by addition of 4NQO and when S. typhimurium TA-100 was treated with 4NQO followed by addition of AE or DA. Marked increases in the level of the BaP mutagenicity were observed only when S. typhimurium TA-100 was treated with surfactants, followed by addition of BaP, in the order of linoleic acid sodium salt>AS> sodium oleate> commercial soap>SDS>DA>sodium myristate>sodium laurate> sodium palmitate. The net number of revertants was positively correlated with the. hydrophile-lipophile balance (HLB) and critical micelle concentration (CMC).

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The budget of the net flux of water and the relationship between load and water quality was studied as the base of water quality management in Seto-Inland Sea. A numerical simulationof the tidal current by levelmodel, data analyses of load and water quality of COD and nutrients and a diffusion simulation of water quality by ΔCOD method were conducted. The main results obtained are as follows.
(1) Computed results of tidal residual current showed an eastward flow pattern flowing from Bungo-Channel and out through Kii-Cannel, and it was in good agreement with the phenomenon of model domain in Seto-inland Sea. The estimated results of vertical advection flux were upward in Iyo-Nada, Suoh-Nada and Osaka Bay and downward in Aki-Nada and Hiuchi-Nada.
(2) The ratio of the retention time for water quality items and the retention time of fresh water could be the useful parameters for the filtering effect of each item, or for the environmental capacity in enclosed sea areas. The ratio was apparently large in the order of COD, TN and TP.
(3) Inner productivity of COD was large in Osaka Bay and Harima-Nada and small in Bisan-Seto. Although Δ COD method was also applicable for water quality control in Seto-Inland Sea, the water-sediment quality simulation and the ecological modelling including fish were thought to be developed for more sophisticated management.

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The purpose of our study is to estimate the influence of development activities on shallow sea ecosystems, especially on fish. An eight boxes two layers ecological model was adopted to the Seto inland sea by using a Shallow Sea Ecological Modelling tool (SSEM). The components of the model were nutrient, detritus, phytoplankton, copepod, pelagic fish (plankton feeder and fish feeder), demersal fish (plankton feeder and fish feeder), and benthos (detritus feeder and benthos feeder). Oxygen deficit was selected as an human impact factor to the fishery environment. The water/sediment interaction model was employed to evaluate the box-average dissolved oxygen concentration. Because SSEM is a box based model, it was difficult to estimated the local oxygen deficit that occurs in rather small water volume. Probability density function of oxygen deficit occurrence was decided based on field survey data from a literature. Oxygen-deficitent water volume to a certain box-average dissolved oxygen concentration was calculated using the probability density function. Although quantitative estimation of stock size by mathematical model are generally thought to be difficult, SSEM seemed to succeed in explaining the distribution of benthos catch in the Seto inland sea by taking the influence of anoxia into account.

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Nitrous oxide (N₂O) is one of the effective greenhouse gases. N₂O concentration in reactors of a full-scale night soil treatment plant was measured and the effects of operating conditions of the plant on N₂O production was investigated. N₂O was produced in the first reactor (intermittent aeration tank) during either aeration phase or anoxic phase. The balance of nitrification and denitrification occurring in the reactor seemed to be a main fa ctor that decided during which phase (aeration or anoxic) N₂O was produced. Dissolved N₂O in the first reactor varied from 0.73-1.25mgN/l to 16.9-24.2 mgN/l depending on the operating condition and other factors. N₂O dissolved in the effluent from the first reactor was effectively consumed in the second reactor (anoxic tank) by denitrification. Addition of methanol into the first reactor as an organic carbon source for denitrifiers was effective to suppress N₂O production in the reactor. Appropriate time ratio of aeration and anoxic phase also seemed to be effective in controlling the N₂O production.

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Interactions among sulfate reducing bacteria, poly-P accumulating bacteria and filamentous sulfur bacteria Type 021N were examined in the activated sludge cultivated with peptone and acetate. When sulfate reducing bacteria grew and the sulfate reducing rate obtained from a batch experiment was great, Type 021N grew predominantly. The sulfate reducing rate was related to the number of sulfate reducing bacteria, and the sulfate reducing rate of a unit sulfate reducing bacteria was about 0.8×10^-8g SO₄/hr. Sulfate reduction and phosphate release were occurred simultaneously in the batch experiment. It was a tendency that when sulfate reducing rate was great, phosphate release was also great. When sodium molvbdate was added to the substrate in the batch experiment, the amount of phosphate release slightly increased. As the results of estimation of the amount of produced acetate by sulfate reducing bacteria from the batch experiments, sulfate reducing bacteria reduced three moles of sulfate and produced four moles of acetate. Sulfate reducing bacteria utilized propionate and/or unknown organic substances produced from peptone.

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Microorganisms that get dominant in the anaerobic-aerobic activated sludge process are known to take up organic substrates under anaerobic conditions. Two types of microoganisms are known to have this ability; one of them utilizes polyphosphate as the energy source under the anaerobic conditions, and another utilizes glycogen instead of polyphosphate. We conducted batch experiments on the anaerobic substrate by two types of anaerobic-aerobic activated sludges, one of them dominated by the polyphosphate dependent microorganisms, and another by the glycogen dependent microorganisms. The anaerobic uptake of acetate, propionate, lactate, pyruvate, malate, succinate, and glucose were examined. And the redox balance and the material balance in the anaerobic substrate uptake were calculated, based on a biochemical model which includes the glycolytic pathway, succinate fermentation pathway, and PHA synthetic pathway. The result showed that both the polyphosphate dependent and glycogen dependent microorganisms take up organic compounds basically in the same way, except for the source of energy for the anaerobic substrate uptake. In order to control the enhanced biological phosphorus process with the anaerobic-aerobic operation, intensive study is needed to understand the interaction between the polyphosphate dependent and glycogen dependent microorganisms.

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Experiments on a proposed dual-media filter were conducted to investigate the effect of filtration rate on its performance in direct filtration with and without coagulation for secondary wastewater effluent. The proposed filter consists of a semi-cylindrical coarse medium bed over a sand bed. Aluminum sulfate was used as coagulant to remove soluble substances and improve turbidity removal.
The results obtained are summarized as follows:(1) The over-all removal efficiency of the filter for turbidity, color, COD and phosphate did not change too much with filtration rate.(2) The removal efficiency of the coarse medium bed and its filter coefficient calculated from IWASAKI's equation decreased with an increase in filtration rate.(3) The length of the filter run decreased with an increase in filtration rate, but the extensibility of the run length owing to high arresting capacity of the coarse medium bed was almost the same regardless of filtration rate.(4) The filter run length was 4-5 times shorter in filtration with coagulation than without coagulation and the corresponding depth of particle penetration in the sand bed, 1.5-2 times greater.(5) The volume of dead void caused by deposition in the sand bed was extremely greater than that of deposits.

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Formulation of denitrification rate of suspended sludge (K_DN) was attempted in the high rate nitrogen removal process using immobilized microorganisms. BOD amount required for denitrification was expressed by BOD balance in the process, and K_DN equation was described as functions of BOD-SS loading (B_L), hydraulic retention time in reactor (Θ), nitrified liquor recycling ratio (R), and proportion of aeration time in Θ(p). KDN calculated by the equation whose constants were determined by experiment was almost proportional to BL and fitted to KDN data. Larger KDN being estimated with smaller p value, it was considered that optimizing the p value is important to improve the overall process performance.

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A mathematical model for the Air-Fluidized-Bed Biofilm Reactor (AFBBR) was developed based on soluble BOD (S-BOD) removal rate, ammonia nitrogen removal rate, oxygen consumption rate and oxygen transfer rate. The caluculated values agreed well with the mesured values. And then simulations were made to evaluate the effect of air feed rate control on the AFBBR by using this model and following results were obtained. Comparing with the constant and equal air feed to every stage of AFBBR, 1) tapered aeration had no advantages and no disadvantages, 2) proportional air feed rate control was effective against the change in the influent feed rate, but not effective against the change in the influent concentration, 3) DO control was effective even when the DO was controlled at only one stage of the AFBBR. And based on the results about the oxygen consumption in this system, the value of the oxygen consumption per BOD removal could be smaller than that of the activated sludge system especially when the S-BOD/Total-BOD (T-BOD) ratio was small.

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Thermophilic Oxic Process (TOP) can be applied to the treatment of highly concentrated organic wastewater. Organic matter in the wastewater is almost completely decomposed and all water of influent is evaporated by this process. In this paper, TOP was applied to the treatment of thickened excess sewage sludge. Caloricity of this sludge is not enough to evaporate all water in this sludge. Therefore, waste food oil was added to increase the caloricity for the acceleration of microbial activity and evaporation of water. The optimum operational conditions were investigated using a 20 1 of reactor and cedar chips as a medium. When the mixing ratio of oil to sludge was 12%(w/w, BOD₅ concentration of mixture was 157, 000mg·1^-1), BOD₅ load was 6.6kg·m^-3·d^-1, moisture content of medium ranged from 50% to 60%, and aeration rate was 2001·m^-3·min^-1, temperature of medium increased to approximately 60°C, organic matter in the sludge was almost completely mineralized to CO₂ and all water in the sludge was evaporated. A minute amount of excess sludge was formed in this process.

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This paper deals with the dewaterability measurement of sewage sludge and its applications. It is reported that a thermal treatment enhances the dewaterability of both primary sludge and waste activated sludge. In order to study this effect more thoroughly, we measured the dewaterabilty and the compressibility of the thermally treated sludges. A newly made air-pressure compression apparatus was used and the effectiveness of the thermal treatment was confirmed. Using the compressibility properties of the sewage sludge measured, the sludge dewatering process was simulated and the numerical solution of this model agreed reasonably well with experimental results.

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To investigate the behavior of non-aqueous phase liquid (NAPL) such as trichloroetylene (TCE) in soil and ground water, one-dimensional column experiments are carried out with pure TCE as a contaminant and four kinds of glass beads (particle size: 1mm, 0.5-0.6mm, 0.18-0.212mm, 0.074-0.125mm) as porous media. In the column, pseudo ground water table is set. In the experiment, the behavior of TCE in the glass column is observed visually and recorded by a video camera. In the experiment with a stainless steel column, a vertical distribution of water and TCE is measured after TCE movement stops. From these experiments it is found that TCE injected into the column initially stagnates at the capillary fringe, and then some of TCE penetrates the capillary fringe and infiltrate to saturated zone. It is confirmed quantitatively that much of injected TCE remains above the pseudo ground water table in the experiment with 0.5-0.6mm and 0.18-0.212mmm glass beads. To remedy contaminated soil and ground water, the behavior of TCE around the capillary fringe and ground water table is very important.

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Experiments on the elution of heavy metals were carried out for three types of rocks (Tuff, Andesite and Shale) under various experimental conditions on pH, rock size, mixture of rocks.
The experimental results showed that Tuff and Andesite increased the alkalinity of water and eluted Mg and Ca. On the other hand, Shale acidified the water and eluted much more heavy metals. Therefore, Tuff and Andesite were defined as an alkali supply rock and Shale as an acid supply rock. It was also found that the smaller size rock eluted much more heavy metals.
In the case that Shale was mixed with Tuff or Andesite, the elution quantity of heavy metals increased, compared with that for an alkali supply rock (Tuff or Andesite). This suggests that the attention should be paid for the use of an acid supply rock in the civilconstruction works.

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Laboratory-scale experiments were carried out to investigate the feasibility of an in-situ denitrification method of nitrate-contaminated groundwater using H₂ as an external electron donnor. To supply H₂, electrodes are embeded into a sandy aquifer and electric currents are applied. Experimental results showed that satisfactory denitrification occured over one year without any addition of inorganic nutrients such as phosphate. Furthermore, clogging problem was not observed, but about two times the stoichiometric current was needed to remove nitrate completely. These results confirm the feasibility of the present denitrification method.

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Because of high burning rate of combustible waste, incineration ash constitutes a large percentage of landfilled waste in Japan. High alkali content in the ash leads to high pH in leachate, which have been seen in many reports of shaking test or lysimeter tests of the ash. However, a couple of lysimeter studies show rapid decrease of pH in leachate, and neutral pH are commonly observed in actual landfill operations. By close analysis of past studies, the authors assumed that carbon dioxide immigration/absorption into ash layer could neutralize pH.
The authors tested the assumption by batch type experiments in this study. Carbon dioxide absorption rate into ash was determined, and good correlation was observed between the absorption amounts and pH decrease in leachate. Though the most experiments were done in carbon dioxide concentration of 30%, the neutralization of pH was also realized in the atmosphere whose concentration is only 0.03%. Finally, model simulation explicitly shows that the neutralization process follows the second order reaction of carbon dioxide and alkali, and the reaction rate constant was estimated.

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It is expected that marginally aerobic layer around the leachate collection pipe has enough capacity to stabilize the leachate in semi-aerobic landfills. To model such marginally aerobic zone, artificial incombustible refuse, artificial mixed refuse and crushed stones were packed in columns respectively and TOC removal capacity of the leachate in each column was measured.
Consequently the following results were obtained.
1) Aerobic decomposition of acetic acid occurred almost as a single reactor condition in artificial refuse and crushed stones layer.
2) Saturation coefficient K_m in Monod equation is estimated to be about 2% in mixed refuse layer, about 1% in the others.
3) When oxygen gas concentration was more than 1-2%, TOC removal efficiency was almost 100% with less than 100g/(m³·d) of TOC inlet load.

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Quality conversion of pollutants in landfill layers was studied through a four year experiment with three semi-aerobic landfill model lysimeters in each of which different landfilling method was adopted. T-N cumulative leaching amount in leachate for 4years reached 37g/t to 84g/t, and TOC 156g/t to 241g/t. Landfill layers become more aerobic with higher air permeability in the layers, so that the T-N leaching amount could be decreased by 45% with improving landfill layers to be aerobic, and TOC by 55%. Leaching amounts of Cl^-, Na and K were 60-70% of the Total Solids. On the other hands, leaching amounts of heavy metals in each lysimeter showed less than 0.1% of the total contents in the solid waste. Decrease in the wastes for 4years was less than 3%(23kg/t to 29kg/t), 53-68% of which was due to leaching and 32-47% due to gasification. Consequently, by improving landfill layers to be aerobic, the leaching amount of organic pollutants decreases and the gasified amount increases.

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A numerical simulation model is suggested for estimating the water quality in tidal urban rivers. The model is composed of two submodels, which calculate unsteady flow and diffusive process of SS and BOD. In the second model, BOD was further divided into dissolved and particulate matter, while SS was divided into organic and inorganic matter. Taking the strong relationship between organic SS and particulate BOD into concideration, water quality was estimated. Some important coefficients in the second model such as self-purification factor and the conversion factor of SS into particulate BOD were determined by field data in a tidal urban river. Introducing these determined parameters into this simulation model, BOD and SS were estimated. Estimated ones well coinsided with the observed ones in the Shinmachi river.

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The investigation of benthic animals in the Tamoki river was conducted in order to evaluate the impact of the river improvement works against the river ecosystem.
The benthic fauna was significantly influenced by the river bed conditions. The benthic fauna destroyed by the river improvement works recovered faster than that by the river flood because the benthic animals lost could be compensated from the upper stream.
The results obtained from this investigation showed that the benthic fauna could be used as an effective index in evaluating the impact against the river ecosystem, which would be brought by the river improvement works.

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