Area-wide waterworks are often planned to resolve water resources problem which cannot be solved by the single municipality. Improvement of water supply stability is one of the effects to be expected by areawide waterworks. Areal definition as a combination of municipalities should be planned in order to get a most effective alternative from view point of the stability improvement. This paper deals with evaluation method of the effect.
Indices are extracted to evaluate water supply stability. Design of experiment method is adopted to make alternatives of area-wide waterworks based on these indices. Factor profile method selects the most effective alternative. Case study gives a practical usefulness of this approach.

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Adoption of area-wide sewerage system has brought about long-term planning problems such as uncertainty of the planning parameters and increasing investment at the initial stage of the project. Time phased construction becomes a present problem of sewerage planning.
This paper discusses the case that the multiple sewers are adopted as the main sewer system. Multiple sewer system has an advantage of sizing flexibility at the intermediate stage, comparing to the case of full-scale construction at the initial stage.
Optional sizing at the initial stage is examined with the present value of expected total project cost calculated by serial demand patterns and its occurrence probability. Case study reveals the advantage of multiple sewer system and necessary conditions to perform the time-phased construction of main sewer system.

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Various pollutants are produced too much in our environment, and they are accumulated on road surfaces, roofs, and open areas. Since most accumulated loads on road surfaces are gathered into street inlets, we never ignor the influences of pollution loads in street inlets on runoff water quality.
So, we derive the model for runoff loads from street inlets which are one of nonpoint pollution sources, in order to make clear the influence on runoff loads on rainy day and the runoff characteristics, and we simulate runoff loads by our model on the basis of the results of runoff experiments.

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Pollutant loadings in dry and wet weathers are observed at Tokiwa and Daini drainage areas that are residential districts. They are 21.3 ha and 1900 inhabitants, 90 ha and 8500 inhabitants, respectively.
The characteristics of pollutant flux are affected by rainfall and rainfall intensity. It is indicated in this study that annual pollutant loadings could be estimated using these equations.
For BOD, D-COD_Mn, TN, D-TN, TP, D-TP
L=365·L_D+R₁·f₁·C₁/100+R₂·f₂·C₂/100
For SS, COD_Mn
L=365·L_D+R1·f1·C1/100+Σa·10_b·Rpn/A
L: Annual pollutant loading (kg/ha·y)
L_D: Pollutant loading in dry weather day (kg/ha·d)
R₁, R₂: Yearly accumulated rainfall for less than 20mm rainfall and for more than 21mm rainfall, respectively (mm/y)
f₁, f₂: Average rate of runoff for less than 20 mm rainfall and for more than 21mm rainfall, respectively
C₁, C₂: Average water quality for less than 20 mm rainfall and for more than 21mm rainfall, respectively (mg/l)
Rpn: Peak rainfall intensity in nth rain of more than 21mm rainfall (mm/hr)
A: Drainage area (ha), a, b: Constant

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11 types of sorption-desorption equations were examined for evaluating breakthrough curve of cadmium. Mathematical models were solved numerically by the Shifting Particle Method and the calculated breakthrough curves were compared with the experimental results.
Some valuable results were obtained under the limits considered. These are as follows;(1) Different from the sigmoid curve, the observed breakthrough curve for cadmium sometimes shows tailing phenomenon;(2) Shifting Particle Method, proposed by G. F. Pinder et al. and improved by K. Ginno et al., was expanded successfully for estimating sorptive materials performances in the saturated zone; and (3) Observed breakthrough curve for cadmium was simulated well by the mathematical model. The model assumed that the cadmium takes two stable physico-chemical forms in the aqueous solution and are sorbed on the soil.

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For most of water quality indicators in a river an annual total loading for the year with more rainfall became larger than that with less rainfall on the basis of the weekly data for two years. Especially, the discharge-weighted mean of nitrate concentration for one year was larger than the arithmetic mean. The frequency distribution of nitrate loading is not normal but skewed logarithmic-normal. These characteristics were distinct in agricultural-land and mountainous rivers and weren't seen for chloride. When the surface runoff occurs during a storm runoff, the concentration and loading of nitrate becomes peaks behind that of discharge, and the concentration keeps up higher level at the recession stage. Because the concentration of rain-water is low, that of river-water becomes a sudden drop by the dilution of surface runoff at the stage of a sharp increase of discharge. Consequently, most of the nitrate load increased by a storm runoff are drained out from the surface soil layer of river basins and carried by subsurface runoff. A specific total nitrate loading during the direct runoff of a storm could be estimated by the log-log regression equation of specific total discharges for many storm runoff events.

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Estuaries plays an important role in the nutrient transport system, but there is only a little knowledge about it. Yamaguchi Bay estuary, which has large tidal marshes, was chosen as the field of this study. By the field work investigation, the following results were obtained; 1) A large ammount of suspended solid is transported upstream during one tidal cycle, under ordinary weather conditions. 2) With this movement, suspended portions of P, N, COD also go upstream, while, soluble portions of them go downstream during one tidal cycle. 3) Movements of chlorophyll-a, suspended solid and C1 ion are different from each other, because the vertical distribution of their concentration and the flowing velocity are localized. 4) Net sedimentation rate of suspended solid in the estuary, caluculated from mass balance or by box model simuration, was 1 to 3 m/day.

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The purposes of this study are to investigate the settling phenomenon of cohesive fine particles and to predict the concentration of suspended solids in quiescent seawater. Experiments on the settling of cohesive fine particles (Kaoline) in quiescent seawater were performed. The mass balance equation for the growth of cohesive fine particles by settling in quiescent seawater was computed numerically by the Monte Carlo method. Assuming the similarity of the particle size distribution, a simplified method for the prediction of the concentration of suspended solids has been developed. A factor of both collision and adhesion, an important parameter with regard to the growth of cohesive fine particles, was studied by comparing the results of the experiments and computation. The numerically computed results show good agreement with experimental results. The factor depends on particle diameter. It is shown that fine particles in quiescent seawater are less cohesive. The simplified method is also applicable to predict the concentration of suspended solids by considering the decrease in the factor due to the growth of cohesive particles.

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In this study, to solve problems on a conventional rotary viscometer, that is, the slip phenomenon of suspension along the cylinder walls, edge effects, and control methods of viscometer, an improved coaxial rotary viscometer was designed and produced, and two simple calculation methods of rheological properties of suspension were developed when the gap between cylinders was wide. The features of this improved viscometer are as follows: 1) The mechanism of transmitting torque was seperated from the mechanism of measuring the rate of shear; 2) A triple cylinder type rotary viscometer was used to minimized the edge effects; and 3) The viscometer was operated at the condition of either constant apparent deformation rate or constant shear stress.
As the simple calculation methods of rheological properties, differential and integral methods are proposed. The former is available when the angular velocity distribution in the radial direction of clay suspension is known over the distance between center and outer cylinders, the latter is available to obtain the relationship between deformation rate and shear stress from the angular velocities near them. Experimental results of clay suspensions with this viscometer differ from the results with conventional viscometers due to the consideration of the slip phenomenon.

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It was shown that a enormous error could appear when convection-dispersion nroblems in infinite domains were solved by Galerkin finite element method assuming an infinite domain by a finite one. Infinite elements suggested by Bettess which easily satisfy boundary conditions at infinity were applied to some convectiondispersion problems and their applicability was examined. Following conclusions were obtained on the problems about a continuous point source in an infinite domain. The best attenuation length contained in a weighting function for infinite elements was found to be proportional to√D_xD_y/v, where D_x and D_y were dispersion coefficients for x and y direction respectively and v, the flow rate. Infinite elements were efficiently applicable to the steady and unsteady problems under the uniform flow fields and the steady problem under the nonuniform flow field.

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Moisture control is required for optimum composting. In this paper, the effect of moisture was examined by measuring decomposition ratio which is dimensionless loss of mass. In benchi-scale composting, temperature was controlled constant at 50°C with the mixture of newsprint and dog food (sample N) or the mixture of sawdust and dog food (sample S). For each run, moisture content was set differently and maintained constant throughout. To make kinetic consideration, Contois' model is used for expressing the time course of decomposition ratio. Since other experiments confirm that it is suitable for composting compared to Monod's model. Fitting of this model, the experimental results show that optimum moisture content is 50 to 60% for both samples, and the ratio of Contois' constant to maximum specific growth rate (k/μm) is the adequate index for expressing the decompositio rate.

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One of the fundamental tactors in selecting a system of co-combustion of dewatered sewage sludge and municipal refuse is a water content of feed sludge to a furnace, namely dewatered sludge or sludge dried by excess heat from the furnece.Comparison of heat balance between two co-combustion systems was carried out in this study. The feed sludge to System 1 and to System 2 was dewatered sludge and dried sludge, respectively. The two Systems had the same units of a gratefired waterwalled combustion unit, a boiler, a generation unit, an exhaust gas treatment unit and so on except a sludge drying unit for System 2. Following ore the results of this study. A. A range of an autogeneous co-combustion ar ratio is wider in System 2 than in System 1. The co-combustion ratio means a ratio of dewatered sludge incinerated to refuse incinerated by weight. B. Comparison of energy costs between the two Systems reveals that System 2 is better than System 1 when autogeneous combustion is not possible, but there is little difference between the two Systems if autogeneous combustion is realized. C. Even if a low heat value is constant, the higher the water content is, the lower the value of sludge as fuel is. In order to solve the problem, new three definitions of heat value are compared with the low heat value.

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A mathematical model was developed to analize the performance of anaerobic biofilm reactor. The biochemical degradation of substrate in biofilm was assumed to aconsecutive reaction. Conservative equations were derived and calculated numerically by using some dimensionless parameters indicating reactor performance and operating characteristics. Effects of the rates of diffusion in biofilm and bulk liquid flow on uptake rates, removal efficiencies and effluent characteristics were clarified.
The following results were obtained.
(1) Intermediate metabolic products are accumulated within biofilm when the value of biofilm property (M) is greater than 2 and the removal efficiency is less than 50%. There exists a region where effectiveness factor (λ_A) is greater than 1 under the condition.
(2) Although the utilization of primary substrate depends on biofilm properties and bulk concentrations of substrate, the utilization of intermediate metabolic products exhibits the different behaviour which depends on biofilm properties and the bulk concentrations or depends on biofilm properties and influent substrate concentration.
(3) The saturation constant in each reaction step evaluated by using bulk concentrations varies with biofilm properties.

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A biological removal of phosphorus and nitrogen by endogenous denitrification process was investigated using a pilot-scale plant. Denitrification rate decrease exponentially as the aeration period preceeding denitrification zone increased. The influent phosphorus concentration, BOD-SS loading, and magnesium and potasium concentration affected the removal of phosphorus.
A laboratory work on the bacterium, Acinetobacter calcoaceticus, which has been considered to be responsible for the biological phosphorus removal, was carried out to clarify the effect of temperature on the growth and its biochemical properties. These results suggested that some micro-organisms other than A. calcoaceticus might be also contributed to the phosphorus removal.

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A multi-staged upflow sludge bed reactor was applied to denitrification process with an aim to enhance the process performance for the treatment of wastewater containing high strength nitrate nitrogen. The denitrifying cells grown in the upflow environment had a tendency to form granular sludge, whose settlability was significantly superior, i.e., SVI of sludge was achieved less than 10 (ml/g). Therefore, the granulation of sludge caused the maximum attainable biomass hold-up in the reactor to be 110, 000 mg/liter as MLVSS equivalence. The retainment of high concentration of biomass leads to increase allowable volumetric loading rate to an order of magnitude greater, compared with that in conventional suspended growth system. From the continuous flow runs varied the influent substrate in the range of 200 to 800 mg NO₃-N/liter, the consumptive ratio, the true growth yield and the maintenance coefficient in USB reactor were evaluated to be 0.82 (g TOC removed/g NO₃-N reduced), 0.334 (g VSS/g NO₃-N) and 0.017 (g NO₃-N/g VSS·day), respectively. The progress of granulation was observed to be associated with the accumulation of extracellular polymer content in the sludge. In addition, the secondary effect of precipitation of insoluble Ca-salts in the sludge granules caused more improvement of their settlability.

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Shallow urban rivers, receiving nutrient-enriched effluent, have thick growths of algae on their beds. Such algae deteriorate the water quality of those rivers by their respiration and detachment from the beds. Therefore it is significant to study the characteristics of the behavior of the attached algae for understanding the water pollution mechanism of the rivers.
In this study, to investigate the effects of the flow on the growth of the attached algae, the algal growth on the surface of a circular cylinder is studied. The cylinder is stood on the bed of an experimental flume perpendicular to the uniform flow and is thought to produce different hydraulic conditions around it.
In the first place the variations of the shear stress and the nutrient flux on the surface of the cylinder are theoretically considered, respectively. Then the way is shown to control those conditions by choosing appropriate values of the velocity of the uniform flow and the cylinder diameter, and the availability of using the cylinder is described.
Next, the experiments are performed following the method described above and it is examined how the shear stress and the nutrient flux at the substratum affect the growth of the attached algae.

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To understand and control eutrofication in natural waters, it is essential to determine what factors are limiting the growth of phytoplankton algae. The statistical analysis and field survey are made about the environmental factors which have influence on extreme algal growth phenomena-water blooms-in the southern part of Lake Biwa. Statistical analysis is based on long-term daily monitoring data-water quality, algal population, and meteorological factors which were recorded by the water supply authority of Kyoto city. As a result, according to the analysis of quantification theory, it is considererd that water temerature, water level, and release rate appear to be potentially important in triggering blue-green algal blooms. Intensive field survey is made to ascertain those factors' effects on algal blooms and to understand the temporal and spatial changes of algal distribution in the lake in summer season. Finally, a simple and practical method to ditermine limiting factors using field survey data is proposed and applied.

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Accuracy of a mathematical model for prediction of eutrophication, which is affected by temporal and spatial scales, has been analyzed in order to provide basic data to determine those scales more objectively. The analysis method is to evaluate accuracy of each submodel for temporal and spatial scales which are different from those in the standard simulation. The following results are obtained.(1) Accuracy of water quality balance model is little affected by temporal scales of proportion of diatoms, water temperature and light intensity.(2) Accuracy of each submodel is strongly affected by a temporal scale of precipitation.(3) Effects of temporal scales on accuracy vary with retention time of a lake. According to the simple model, if retention time is less than 5 times temporal scale of an input function, variation of an output is greater than 10% of that of an input.(4) Accuracy of outputs on water quantity is little affected by a spatial scale of the watershed of South Lake (the southern basin of Lake Biwa), but accuracy of outputs on water quality is strongly affected. Accuracy of load model is more important when determining a spatial scale of a watershed.

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Mud sumples were collected from Lake Kasumigaura in July 1981. Grading curve, water content, specific gravity and iginition loss of the samples were measured. The vertical profiles and horizontal distributions of these parameterss are discussed. The distribution characteristics, especially those of the grading curves, changed distinctly at 0.3m deep. Mud samples less than 0.3m deep had larger mud particle diameters and higher ignition loss than those bellow 0.3m and showed regional differences. The region from Takahamairi Bay to the center of Lake Kasumigaura had the largest diameter, the highest water content and ignition loss and the lowest specific gravity. Distributions for cases more than 0.3m deep showed little regional differences. Apparently some big change occurred in the environment about Lake Kasumigaura at the time bottom sediments about 0.3m deep accumlated. Taking into consideration the vertical changes in water content of bottom sediments layer, we estimated that this sediment had accumlated about 65-85 years ago. It was found almost all the annual accumlation rates as determined by some researchers are basically in agreement with ours although there are some differences in their expressions.

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Deposition of seston, chlorophyll-a, and nutrients in Lake Chuzenji, which is oligotrophic lake with 163m maximum depth, were observed every one month for two years. The annual amounts of deposition at 110m depth were obtained to be 1241, 0.582, 52.6, 5.83, 1.27g/m²y for seston, chlorophylly-a, carbon, nitrogen, and phosphorus, respectively. On the basis of the content of Ti, the separation of deposited matter into allochthonous and autochthonous matter was examined. The decomposition rates during sedimentation and at sediments were estimated from those data. The significance of deposition of particulate matter was discussed with the observed input fluxes. Particularly, those phenomena expained the low value of dissolved oxygen near sediments and the increace of NO₃-N in lower layer in stratified period. The average values of sinking rate were calculated to be 2.5m/d for seston, and 0.67, 1.19m/d for chlorophyll-a at the depths of 30m and 110m, respectively. In addition to the cross correlation of those rates for each sampling period at each depth, the content of chlorophyll-a in seston effects the sinking rates of seston and chlorophyll-a

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The concentration of sulfide in the mud of many polluted water basins in Japan practically exceeds 0.2mg/g dry mud, the fishery standard.
In this research on Lake Barato (fresh water, partially brackish water) in the suberbs of Sapporo city and on Otaru Canal (sea water) of Otaru city which is connected to the Bay of Ishikari, I comprehended the actual condition of sulfide in the mud measuring its concentration and the number of sulfate reducing bacteria which form it, and I made its formation mechanism clear by laboratory work.
The resultes of this research are as follows:
(1) Sulfide in the mud of these water basins (especially sea water basin) polluted by the urban waste water exists in proportion to organic content and exceeds far beyond the standard.
(2) Sulfide as iron sulfide accumulates more in sea water than in fresh water.
(3) The sulfide formation rate is influenced by temperature but not by concentration of sulfate nor the number of sulfate reducing bacteria.

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