The water quality data of the Sagami River at 12 stations from April 1976 to March 1980 were analyzed by the Principle Component Analysis (PCA) method.
Water Quality Index (WQI), which was proposed in this paper as an evaluation of the pollution level as caused by human activities, was reached as follows. First, the test of normal distribution was carried out for 10 water quality items and the most appropriate tarnsformation type that brought each item closer to normal distribution was selected among the three types, i.e., original data, square root and logarithm. Next, PCA was performed by using the transformed data. The first component of PCA with 10 items was ascribed to the pollution caused by human activities. Then the 6 items (DO, BOD, COD, PO₄-P, NH₄-N and NO₂-N) which showed high contribution to the first component were selected for the further analysis. The equation derived from the first component of PCA with 6 items was used to evaluate WQI.
WQI at 11 stations displayed little or no yearly change except in 1978. In 9 stations, WQI at night was found to be worse than daytime WQI. Such characteristics could not be obtained by analyzing only BOD data.
The relationship of WQI with natural and social factors in the tributary basins was also discussed. The results showed that there was a high correlation between WQI and flow rate, basin area and population density factors.

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Fortysix processing industry plants of wastewater treatment that utilize only secondary activated sludge were checked on concentrations of phosphorus in their influents and effluents to estimate the environmental (BOD, COD, T-N and P) loading form this source. While influent levels of 17.7 mg/l were reduced to 6.2 mg/l (as P) in the effluent, an overall removal of about 65%. The remainder is still high enough to contribute significantly to the accelerated eutrophication of freshwater stream, lakes and marshes as well as the marine waters in some coastal areas of Japan.
Therfore, a pilot plant study was initiated to investigate the further removal of phosphorus from these processing industry wastewaters though the use of chemical coagulants such as aluminum sulfate, ferric chloride, and calcium hydroxide. The pilot plant data showed increases in efficiency of phosphorus removal to more than 90%. Moreover phosphorus contents in the sludge and weight of sludge were measured.

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On the biological index of the river water pollution and contamination was carried out by the BGLB/36°C, BGLB/44.5°C and EC/44.5°C method of Coli-form test (MPN). Results obtained were as follows.
(1) There was a high correlation between the MPN from EC/44.5°C method and BGLB/44.5°C method, and the MPN of fecal Coli-form was 4.7 to 10.7% of the MPN of total Coli-form.
(2) Each fitted rate of the environmental quality standard in Japan obtained by BGLB/36°C and BGLB/44.5°C method was 48.5% and 95 to 100% respectively.
(3) Fitted rate from BGLB/44.5°C method against 1/10 value of the environmental quality standard was 66.7%.
(4) Fitted rate with the MPN from BGLB/44.5°C method parallels more closely than that the MPN from BGLB/36°C method on the fitted rate of BOD.
(5) There was no considerable difference between the BGLB/36°C method and BGLB/44.5°C method against the results of SS (C), BOD (D) and TOC (E).
(6) It was suggested that the rate of fecal Coli-form isolated from BGLB medium at 36°C incubation method is more closely correlated with the MPN from BGLB/44.5°C method than that from BGLB/36°C method.

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The effect of NO^-₂-N on the denitrification by N-1 strain at different temperatures was investigated.
The additional dosage of NO^-₂-N in the course of denitrification gave no effect on the removal rate of NO^-₃-N. When NO₂-N was contained in medium, the denitrification was greatly inhibited at 5°C, but it was not heavily inhibited at 10°C. Aerobic growth of N-1 strain was inhibited by 2 mM NO^-₂-N at 5°C, while 7 mM NO^-₂-N gave no effect at 10°C. The results of the denitrification using the resting cells indicated that N-1 strain produced unknown factors which stimulated the denitrification in the filtrate of anaerobic culture solution.

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