Filamentous organism in activated sludge was quantitatively expressed in terms of both filament length and filament volume per unit weight of dried sludge and the former was defined as specific length of total filaments and the latter specific volume of total filaments, respectively.
In the determination of specfic length of total filaments, length of filaments was measured by counting number of intersects between filaments and grid lines in a square according to Olson's method. Specimens for the measurement of istersect number were prepared as follows :
1) A sludge sample was homogenized with a blender.
2) After making a series of dilution, the diluted samples were filtered.
3) Optical density of filaments on the filters was increased by staining with basic Fuchsin.
4) After driing, the filters were made semi-transparent on slide glasses using an immersion oil.
The intersect number was counted either directly with a microscope attached an ocular squares micrometer or on microscopic photos.
For the determination of specific volume of total filaments, filamentous organisms in an activated sludge were classified to types based on the morphological feature and then width and specific filament length were determined for each type of filamentous organisms.
Furthermore, after the sources of error were examined, the magnitude of error was designated in an equation for each quantitative filament determination.

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In the previous paper, one of the authors showed a method to determine the quantity of all filamentous organisms in activated sludge by both filament length and filament volume per unit weight of dried sludge. The former was defined as specific length of total filaments and the latter specific volume of total filaments, respectively.
In this paper, relationship between these quantitative estimates and bulkiness of activated sludge was examined using activated sledges obtained from various treatment plants. The bulkiness of activated sludge was determined using Standard SVI at 20 C.
Following aspects were indicated.
1) Increase of filamentous organisms in activated sludge made the sludge more and more bulky.
2) Specific volume of total filaments showed higher correlation to Standard SVI than specific length of total filaments did.
3) Bulking of activated sludge may occur at about 2 per cent of filament content in activated sludge organisms.

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The effects of interruption of wastewater inflow on the performance of rotating biological contactor processes (RBC) were studied using laboratory scale RBC processes. The processes used in this study were placed in temperature controlled rooms of 10°Cand 20°C. The processes were operated with hydraulic loading of 53^l·m^-2·d^-1 and BOD loading of 8.0g·m^-2·d^-1.
The following results were obtained.
1) Immediately after the reintroduction of wastewater, effluent COD values increased up to about 27mg·^l-1 and about 35mg·^l-1 for 3 days and 7days interruption, respectively. However, the effluent COD values decreased to the same level as that before the interruption (COD =1020mg·^l-1) within one day. Little difference was observed between operations under 10°C and 20°C.
2) The increase in the effluent COD was estimated to be caused by decomposition and dissolution of microbial film during the interruption. However, organic removal efficiency of microbial film was not decreased during the interruption of wastewater inflow for several days.

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A method of determination of fluorescent whitening agents (FWA) in river waters and sediments by high performance liquid chromatography (HPLC) was studied.
Six kinds of FWA could be separated according to following conditions; column : ODS SS-10-B 4mm i.d. X 250mm, mobile phase (a) 0.011 NaH₂PO₄ -acetonitrile (75 : 25v/v), flowrate : 1.0m^l/ min.
FWA in the column effluent were monitored with fluorescent detecter (E_x=358nm, E_m =403nm).
FWA in river waters were adsorbed on SEP PAC cartridge and eluted with methanol. FWA in river sediments were directly extracted by shaking with methanol successively three times.
Each extract was evaporated to dryness and dissolved in the solution of water-acetonitrile (70 : 30v/ v) for HPLC.
From river waters and sediments of the Sagami river, two types of FWA (FWA I and FWA II), the same as used in the detergents, could be detected.
For the rapid quantitative analysis of FWA I and FWA II, it was found to be effective to use mobile phase (b) 0.1% tetraethyl ammonium perchrorate in water-acetonitrile (70 : 30v/v). Then peak heights were linear with FWA amounts in the range of 010ng for FWA I and 01ing for FWA II.
By the proposed method, FWA in river waters and sediments of the Sagami river were determined as follows ; FWA I : 0.09-3.4μg/g in sediments, FWA II : 0.85-4.4, μg/^l in river waters, 0.1410.7μ g/g in sediments.

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The authors reported in the previous paper that the Water Quality Index (WQI) derived from the Principle Component Analysis (PCA) method for the Sagami River could evaluate the pollution levels caused by human activities fairly well.
This time, in order to obtain more general and more reliable WQI, the water quality data of the 11 items collected at 72 stations in the 27 rivers which flow through the Kanagawa Prefecture were analyzed, and especially careful attention was paid to pre-treatment of the data.
As the pre-treatment of the data, exclusion of outliers by Masuyama's method and Iwai's method which correct skewness, were applied besides the test of normality for the three kinds of transformation types, i.e., original data, square root and logarithm.
The 4 items (DO, BOD, PO₄-P and NH₄-N) were chosen for inclusion in WQI on the basis of the results of the PCA with 11 items. Then, the first component of the PCA with 4 items was used to evaluate WQI.
This WQI was able to be classified reasonably well and the water quality map was drawn according to the classification. This map was found to be a useful tool leading a better understanding of the river water pollution.

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Water quality characteristics of R. Kakogawa in Hyogo Pref. were analyzed statistically by the time series data for the years 1972-1980.
Concentrations of SS and Coliform had spacial and time-dependent variations markedly, whereas pH value varied little. The concentration of Cl- was positively correlated with an increase in the concentration of organic pollutants and negatively with an increase in the magnitude of flow. It was found in several water quality parameters that many sites had common seasonal variations in this river basin.
From the principal component analysis based on the correlation matrix of six parameters (BOD, COD, SS, Coliform, Cl^- and DO^5at.), the first component (Z₁) was identified as the water pollution factor. Because of the similarity of long-term variations between Z₁ score and census data, it is presumed that water pollution in its middle reaches is caused primarily by the effluents from the textile and dye factories in and around Nishiwaki City.

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The mechanism of eutrophication in embayments was investigated in Hakata Bay that is located on the northern part of Kyushu Island. On the basis of the results of the field survey, two numerical simulation methods for the prediction of COD concentration were discussed. The first method was the ΔCOD method in which the COD concentration derived from phytoplankton production was expressed integrally with the concentration of nutrients. The other one was the productive function method in which the rate of internal COD production was represented as the function of the concentration of the nutrients.
As a result of field survey and the numerical simulation the coefficients of sedimentation velocity, primary production rate, and decomposition rate were obtained. Thus the mass balance of COD and nutrients in Hakata Day were identified. In addition, two simple and useful methods for the COD prediction, the COD method and the productive function method, were indicated.

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