Area-wide waterwork is one of the strategies to resolve the water resources problems which cannot be resolved by the effort of the single municipality. If the area-wide waterwork is defined as an association of several municipalities, combination of them is a basic frame of the planning. This paper deals with the combination as the problem of areal definition of the area-wide waterwork.
The association of the municipalities is assumed to be composed by pairwise relations among them. These relations are described as matrices of some factors in geographical and socio-economical conditions. Component analysis II, referring to the actual establishments of area-wide waterworks in Japan, gives the weights of the factors to evaluate the likelihood of the association on each pair of municipalities. Cluster analysis provides the hierarchy of municipalities based on their likelihoods to make an area-wide waterwork. Areal extent of the area-wide waterwork could be determined on this hierarchy. Case studies are undertaken in two different regions to discuss the validity of this approach.

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In planning and design of a wastewater treatment plant, it is important to understand the biological reactions that affect the quality of plant effluent and to set up water quality goal. There exists a problem concerning the BOD analysis when NH4-N is nitrified in a wastewater treatment process. In the case when NH4-N coexists with nitrifying bacteria in the effluent, the oxygen demand for the nitrification (N-BOD) increases.
This paper presents some examples indicating that the nitrification in an organic oxidizing process affects the BOD values in the effluent and proposes a plant design procedure controlling nitrification and maintaining low N-BOD value, although some quantitative considerations are still needed. Water quality goal of a wastewater treatment is affected by river conditions and water quality criteria, therefore, such treatment plant design parameters as capacity and BOD loading of plant facilities should be determined taking these factors into account. Keeping the difference of nitrogen composition in the effluent in view, the behavior of NH4-N in a river is studied and treatment plant design parameters are evaluated for the case that NH4-N concentration in the effluent affects the use of river water.

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Various pollutants are produced too much in our environment, and they are accumulated on road surfaces, roofs, and open areas or in drainage ways and sewer pipes. These loads are flushed out by runoff water in rainfall and become one of factors of water pollution in receiving water.
For preventing the water pollution and improving the quality of receiving water, it is necessary to control the pollution runoff from non-point sources by some way. For this purpose, it is important that we make clear the runoff mechanism of pollutant from nonpoint sources and estimate the runoff loads quantitatively.
In this paper, we made clear the runoff characteristics of separate sewer systems which is one of ways of runoff loads from non-point sources, and built up the model which express these runoff characteristics. We simulated runoff loads in each rainfall and in each water qualities by our models. We get good results that simulated value by these models almost agree with measured value it will be possible to calculate the runoff loads of the flushing of separate sewer systems in many districts.

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Because storm runoff loading in a river is larger in comparison with loading in same period of dry weather day, the author proposes following regression models to estimate its loading. Plotting the relationships between sum of loading a unit area (ΣL_gross/A) and sum of flow a unit area (ΣQ_gross/A) in direct runoff period by storm events on logarithmic paper, the points are in a restricted range and are expressed as an exponential equation, ΣL_gross/A=a·(ΣQ_gross/A) ⁿ, by regression analysis. Similarly, for net loading by direct runoff (ΣL_net) which is substracted sum of loading in same period at dry weather day (ΣL_base) from ΣL_gross, a regression equation is obtained with net discharge (ΣQ_net), ΣL_net/A=a·E (ΣQ_net/A) ⁿ And also, net loading a unit area (ΣL_net/A) could be expressed as regression equations with ΣQ_net, observation period (T_dir) or rainfall duration period (T_rain) and area of basin (A) as following:ΣL_net/(A·T_dir) =a [ΣQ_net/(A·T_dir)] ⁿ;ΣL_net/A=a·[ΣQ_net/(A·T_rain)] ⁿ. Using observation data (28 cases) of influent rivers into the Lake Kasumigaura, regression equations of four types are obtained for almost all water quality indicators with high regression coefficients. Especially, these four regression models could be applied not only for total and particulate component loadings but also for dissolved component loading.

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The mechanism of the rolling-up phenomenon has not been sufficiently analyzed in that the sediment material is small, cohesive and of mixed organic matter. Numerous data obtained to date are from fragmentary or overall measurement on hydraulics and rolling-up rate. Consequently, the systematical study on the fundamental factors, to be used for forming a model of this phenomenon and to evaluate its appropriateness, has not been attempted. Therefore, the factors presiding over the phenomenon are considered in this paper, from the optimum combinations in many kinds of physical quantities with the dimensional analysis, and then the existence of sediment transport and density current in this phenomenon are explained with these nondimensional parameters.
Results are as follows: The coefficient of condition is combined with the 3rd power of nondimensional shear stress, the 6th power of Keuligan number and the -3rd power of friction velocity coefficient, and is related to the Galileo number. This coefficient is the most important parameter to determine the occurence of sediment transport or density current phenomenon on the mud surface. When the water content in mud is decreased, the nondimensional rolling-up rate is proportional to the 1st power of nondimensional shear stress. On increasing the density and viscosity, the layer neighboring the mud surface grows with the mud which is supplied from the lower layer by shear stress, so that the three layer model is expected to apply in the concentration distribution. The sediment transport phenomenon is observed on the mud surface. In the other case, i.e., on increasing the water content, the nondimensional rolling-up rate is not only proportional to the 4th power of the nondimensional shear stress, but the density current phenomenon is observed on the mud surface. When these concentrations in the two layers (lower and middle) are of the same values, the middle layer becomes extinct, and is expected that a two layer model can be constructed.

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In this study, I mainly examined the characteristics of algal growth potential of urban polluted waters and the relationship between them and the forms of nutrients. For these purposes, I made AGP tests (applying the method of Sudo and others (1981), inoculation with Microcystis aeruginosa) and MBOD tests applying the method of Nakamoto (1978) on waters pretreated in various ways (non-treatment, autoclave treatment, filtration treatment, and so on) which were sampled from rivers and lakes near Sapporo city in winter. Together with the tests above, the forms of nutrients especially of phosphorus were analyzed. As the result of these experiments, it was recognized that the maximum algal production of polluted urban waters were limited by the concentration of phosphorus, especially by particutate reactive phosphorus, the dominant form in many cases. It was also recognized that the influence of the existance of bacteria to the algal growth is not so much. In addition, through this study, MBOD test that is advantageous of short testing period (5 days) is fairly effective of predicting the quantity of algal production, but it was observed to have the tendency to underestimate the contribution of particulate nutrients to some extent.

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Authors propose a simple and practical method for estimating the growth rate of algae in nature using field survey data. This method is applied to the southern part of the Lake Biwa.
The estimated growth rates by this method are compared with other items of water quality data (N, P). The estimated growth rates are also compared with AGR values.(AGR value is computed from the resultant reproduction curve of a laboratory algal assay procedure-AGP and AGP^M test.)
As a result of comparison, there exists positive correlation between them, that is, Monod type functional relation is partically true. This relation, which is also derived from the theoretical consideration, shows that AGP values are equivalent to nutrients'concentration in evaluating the lake eutrophication state.

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Nowadays, lake eutrophication, especially extreme algal growth phenomena, affects significantly drinking water resources and causes heavy damage to water supply systems. Therefore, analyses of algal growth mechanism and model construction of algal population dynamics are necessary for the conservation of water resources. This paper discusses a computer model for simulating algal population dynamics and spatial distribution in the lake, which is based on the hydrodynamic characteristics such as vorticity and retention time. Spatial distribution of vorticity and currents in the lake are computed by the 2-dimensional vorticity-stream function model.
Next, a biological submodel describes the algal population distribution. This hydrodynamic process oriented model is applied to the southern part of the Lake Biwa.
As a result, vorticity, which is considerd the extent of local water circulation, makes substantial retention time of algae and affects algal growth process as well as nutrient condition.

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This essay is a report on the mechanisms for the musty odour production in the lake Kamafusa where is located in the nothern part of Japan. The investigation and analysis are made about the condition and the prediction for the musty odour production, identification of the odorous compounds and the effect to the water flows in the lake.
As a result, Actinomycetes as odour producing aquatic organism is turn into Phormidium tenue because the change of the biota which is caused by the cold-weather in summer season in 1980.
From the cultivation by Phormidium tenue, the threshold odour value increases following to the increasing of Chlorophyll-a. And it is confirmed that the musty odour compound of Phormidium tenue is 2-methylisoborneol by the qualitative analysis.
According to the analysis of quantification theory, it is considered that the duration of higher temperature and insolation beyond the average value is effective to the musty odour production. Moreover, the threshold odour value is getting higher with the raise of water level.
To anticipate, the method of“effective accumulated temperature” is applied to the musty odour production and it is indicated it's efficiency and the numerical value.
It is observed that the horizontal and vertical circulations are formed in the lake. Furthermore, it is found that the wind-driven current effects directly upon the diffusion of musty odour.

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Lake surveys and in-situ experiments were conducted to study the dissolved oxygen budget in natural lake and artificial lake. Differences of dissolved oxygen budget in each stage of summer stratification were studied on Lake Yunoko (surface area = 0.33 km², maximum depth = 12.5m, mean depth = 7.4m). Lake Kamafusa is a artificial lake (surface area = 2.66kni, maximum depth = 33m at elevation of 148m), which was surved to compair the difference of dissolved oxygen budget from Lake Yunoko. A mathematical model, in which the production of oxygen by photosynthesis of phytoplankton, the consumption by respiration of microorganisms, sediment oxygen demand, and oxygen transfer by the eddy diffusion and reaeration at the surface of water were taken into consideration, was developed to estimate the dissolved oxygen budget in the lake. The results of this research are as follows.
(1) In a first stage of stratification in summer, that the sediment oxygen demand (SOD) played significant role on largest deficit in DO at the bottom layer.
(2) After the hypolimnion becomes a low level in dissolved oxygen in such lakes, water column oxygen dmand was dominating facters rather than the others facters.
(3) Significant oxygen depletion in the hypolimnion was not observed in the presence of small oxygen demand in sediment and/or large amount of oxygen transferred from upper layer to deeper layer.

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Characteristics of variation of water quality, which are effected by lake topography, input variation, and variation of rate constants, govern the sampling method in a lake. For the purpose of long-term monitoring of water quality, modelling of water quality variation in a shallow lake was tried by the use of system analysis method after the classification of the lake to apply completely mixing model and the lake to apply advection-dispersion model. Prediction of characteristics of water quality was obtained for second-order moment with the aid of frequency response and for probability distribution with the aid of unit impulse response under the conditions of input fluctuation and variation of rate constants. Considering the effect of sampling at equal intervals to the variation of low frequency and the effect of biassed probability distribution on interval estimation, sampling accuracy due to the number of sampling in a year was evaluated. These results were applied to Lake Kasumigaura and successfully discussed.

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The statistical data of municipal water supply were analysed to assess nitrogen pollution of groundwater in each prefecture of Japan. The weighted mean concentration of nitrate plus nitrite nitrogen in groundwater for all over Japan was 1.33 mg·L^-1 in 1970 F. Y., 1.10 mg·L^-1 in 1975 F. Y. and 1.28 mg·L^-1 in 1980
F.Y., and no abvious trend was found. The weighted mean concentration of shallow well water for all over Japan was about 1.6 mg3·L^-1 in these three years which was always higher than the concentration of any other groundwater such as deep well and spring waters.
To compare with the above result the mean nitrogen concentration in groundwater was estimated supposing that nitrogen loaded the ground from such sources as domestic wastewater, chemical fertilizer, and livestock and poultry wastes would be uniformly diluted with effective rainfall. The estimated mean nitrogen concentration in groundwater for all over Japan was 2.00 mg.L^-1, which was approximate to the actual weighted mean concentration of nitrate plus nitrite nitrogen in groundwater. From aspect of contribution to groundwater nitrogen pollution, chemical fertilizer had the largest proportion, and livestock and poultry wastes the second largest, and domestic wastewater had only a negligible proportion. The actual and estimated nitrogen concentrations in groundwater in each prefecture did not always agree with each other, and the reasons were discussed.

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Optimum allocation method was proposed and simulation studies were executed for allocating monitoring wells around an assumed municipal solid waste burial site by use of a computer. The problem to allocate monitoring wells was formulated as a multi-objective design problem and was tried to solve based on utility assessment techniques.
Environmental monitoring system should detect the release and transportation of hazardous materials through groundwater zone infallibly, rapidly and redundantly as well as economically. The objective function was described with a total utility function which was to be determined by adding up each three attribute (e. g. rapidness, redundancy & economical superiority) utility functions, and the optimum alternative was selected as one with maximum total utility.
Two dimensional convective dispersion equation was solved numerically to get travel time distribution of a hazardous material, which should be used for determining utility value of each attribute under appropriate conditions.
Some examples of optimum allocation of wells were shown and the characteristics of the optimum alternatives and the proposed allocation method were examined.

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Biological degradability. of sewage sludges was studied by aerobic and anaerobic digestion experiments. The following results were obtained.(1) The primary clarifier sludge produced at lower overfolow rate was more rapidly decomposed than that at higher overflow rate in the batch aerobic digestion process, while the difference was little in the anaerobic one.(2) In the batch aerobic digestion process of waste activated sludge, the ultimate decomposition level became higher as the overflow rate of primary clarifier was.increased.(3) In the semi-continuous digestion process of mixed sludge, the specific decomposition rate in the anaerobic digestion at 37°C was fairly higher than the aerobic digestion at 20°C for short digestion time, while the difference was little for long digestion time.(4) The percentage of anaerobic decomposition was rapidly incrersed for 10 days and was nearly the same after then. The highest percentage was 93 on a basis of the degradable mass. The soluble COD was not increased in the digester until- about 6 to 8 days.(5) In the anaerobic digestion process of the mixed sludge oxidized.by the preceding aerobic digestion, the solid liquefaction rate in the early stage was not so affected by the remaining degradable mass, while the overall gas production rate per decomposed volatile solid was reduced by about 25% compared to the original value of 800 ml/g of the mixed sludge.

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Acidogenesis from a powdered whole milk solution in a CFSTR at 37&C was studied over the pH range from 3.6 to 7.0 and HRr range from 6 to 30 hours, with respect to the decomposition of the constituents and the product distribution. The decomposition ratio of carbohydrate and protein ranged from 95 to 100 and from 20 to 50 percent, respectively. Only less than 10 per cent of lipid was decomposed at all pH values and all HRT values. As for the fermentation products, acetic acid and propionic acid were the main products in the higher pH range and the longer HRT range, while butyric acid appeared in high concentration in the lower pH range and the shorter HRT range. In order to investigate the effect of phase separation on the methanogenesis, the mixed liquor of the acid reactor and the unacidified substrate were inoculated with a methanogenic sludge from a single-phase digester. Retardation of acidogenesis from the unacidified substrate, probably because of the temporal accumulation of higher fatty acids, was observed, while the mixed liquor of the acid reactor was acidified and converted to methane without retardation.

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The acidification of whole milk (4, 500 mgCOD/1) in anaerobic digestion was investigated to obtain more information on the acid phase, including both hydrolysis and fermentation, at low temperature. Four continuously-fed digesters with hydraulic retention times (HRT) of 12, 24, 36 and 48 hours were operated at 20&C and one with HRT of 24 hours at 37&C. Based on equivalent COD, about 30 to 40% of substrates were degraded at 20&C when operated at HRTs of 12 to 48 hours and 38% at 37&C, demonstrating that a little increase of HRT could make up for the decrease of bioactivity caused by lowering temperature. Of the substrate constituents, carbohydrates were most extensively utilized (95%) and next proteins (60%), while only 30% of lipids decomposed. The change of methane content in gas phase indicated that the growth rate of H^2- utilizing methanogenes was greatly increased between HRTs of 12 and 24 hours, although methane production was always less than 4% of substrate COD. The hydrolysis rate was described by a first order reaction as a function of biodegradable unsoluble matters remaining and not directly related to the cell concentration within its range of this experiment. Values of the kinetic parameters determined at 20&C were 0.179 hour^-1 for the hydrolysis rate constant, 0.385 g cell COD/g COD utilized for the cell yield and 0.00036 hour-1 for the cell decay.

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The inhibition process in composting was examined using newsprint and dog food as substrates. In the studies, it was often observed that there was apparently little amount of oxygen consumption when compost had a low pH. It was found that the inhibition was mainly due to the formation of lower fatty acids and the eventual decline of pH. To know the effects of pH and lower fatty acids on composting process, oxygen consumption was measured at different pH which was controlled with acetic acid, sulfuric acid, ammonia and potassium hydroxide. In all cases, the optimum pH for oxygen consumption was in the alkaline phase. On the other hand, little oxygen consumption was observed in the acid phase. The decomposition rate of acetic acid was also studied by dosing acetic acid to ripe compost. There was time lag before decomposition of dosed acetic acid began. The lag time was prolonged exponentially with the increase of its dosing level. However, dosed acetic acid was decomposed rapidly after this lag time.

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Experiments on finding the role of sulfate reducing bacteria in an anaerobic fluidized bed reactor were conducted with the substrates of a refined soybean protein and amino acids. Soybean protein consists of 60% of the soluble part and 40% of the suspended particle part. The soluble part of the protein was rapidly decomposed into organic acids in the reactor with the hydraulic retention time of 25 min. The organic acids were converted into acetic acid with reduction of sulfate, which meant the role of sulfate reducing bacteria was to convert certain low molecular organic acids into acetic acid. If the sulfate concentration in the influent is kept at the optimum ratio to the concentration of the protein, acetic acid occupies 44 to 76% of total organic acids in the effluent. A mixed substrate of 14 amino acids was also used for the influent of the reactor and showed high decomposition of the amino acids ranging from 23 to 95% decomposition for each amino acid. The reduction of sulfate and production of acetic acid were also observed. When single amino acid of 10 kinds was used for the substrate, decomposition and sulfate reduction were poor for most of the experiments. The stickland reactions of combinations of glycine-alanine, glycine-valine, glycine-leucine and arginine-leucine were investigated in the reactor. Compared to the experiments of single amino acid substrates of 10 kinds, the decomposition of all amio acids were more poor in the reactor.

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We have developed the sludge settling analyzer which provides with the additional functions to automatically measure the supernatant turbidity in the settling column and to analyze the settling properties from settling curves, besides the measurement of sludge volume index (SVI). Settling test studies using this apparatus were conducted to determine the settling parameters in the full-scale activated sludge process under a variety of operational conditions. As a result, the settling curves can be expressed in the form combined with the two settling zones, that is, both hindered settling and compression regions. These parameters such as initial settling velocity (ISV), Roberts' constant (k_r) and compaction point (t_c, H_c) are shown to be expressed as a function of SVI. It has been found that supernatant turbidity is well correlated with 30 min settled volume (SV₃₀) or ISV. Therefore, these parameters are available for the designs and process controls of the secondary clarifiers

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The development of effective simultaneous removal processes of nitrogen and phosphorus have been desired, since environmental standards for nitrogen and phosphorus in lakes were set in December, 1982. In Hamamatsu City, attempts have been made to remove nitrogen and phosphorus simultaneously from wastewater at two smaller-sized sewage treatment plants in order to prevent entrophication as well as to conserve water quality in Lake Hamana. These treatment plants are operated with alternative simultaneous nutrients removal processes by making use of the existing treatment facilities designed as the extended aeration system. In these processes, internal carbon sources and / or endogenous respiration is exploited to achieve dissimilatory reduction of nitrate to nitrogen gas, and phosphorus removal can be accomplished by biological excessive uptake of phosphate. The following conclusions were derived from full-scale operations at Kotoh sewage treatment plants. At higher water temperature, excellent treatment pertormances in terms of organic substances and nutrient salts were obtained consistently. On the other hand, it was required sophisticated SRT (sludge retention time) control to achieve satisfactory nutrionts removal at lower water temperature: longer SRT was required for complete nitrification- denitrification reaction, whereas excessive SRT might have adverse effects on the biological phosphorus removal.

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In this paper we deal with the BOD oxidation, nitrification and denitrification in one aeration tank. Although this system has very simple and noticable characteristics, the mechanism of removal isvery complicated, and the modeling of the phenomena has not been established because BOD oxidation, nitrification and denitrification occur concurrently and succesively. Authors were rearranged this phenomena as biochemical oxidation-reduction system, and were treated kinetically. It was concluded from the results, which are:(1) The sum of all bacteria is regarded as one kind of the biomass to be considered. Every bacteria in the biomass acts as a metabolic tissue.(2) Organic carbon and ammonia nitrogen compete as an electron donor in the biochemical oxidation-reduction system (3) dissolved oxygen and nitrate (nitrite) ntrogen compete as an electron accepter.
From these computer simulations, successful results to explain these complicated phenomena.

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Denitrification processes in soil columns were investigated under the continuous leaching of KNO₃ solution. Temporal evolution of concentration profiles of NO^-₃-N, NO^-₂-N, and NH⁺₄ -N in the soil columns were measured after the step application of solution. Steady-state profiles of NO^-₃-N were linear, which shows the zeor-order denitrification. The zero-order rate coefficients of the experiments were estimated using the mathematical solution of the convective-dispersive equation with reaction.

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