Development of an effective operation method of sequencing batch reactor activated sludge process with intermittent to remove nitrogen, phosphorous and organic substances simultaneously from wastewater was studied by using the laboratory scale apparatus. This treatment process is made up four stages.
First, the wastewater is inflowed into the tank with agitation in the anaerobic condition until the wastewater is filled in the tank. At second stage, aerobic reaction and anaerobic reaction are conducted alternatively by intermittent aeration of activated sludge in the tank. The solid-liquid separation are conducted at third stage and the suppernatant is effluented from the tank at last stage.
The results obtained from this study are as follow.
(1) At first stage, the suitable agitating time for removing phosphorus effectively in the wastewater was from 15 to 120 min. (2) The wastewater was effectively treated when the NH₄-N concentration in wastewater was kept about 0.5mg·l^-1 at the final point of intermittent aeration of second stage by controlling air volum. (3) The suitable agitation time was 60 min. per once in intermittent aeration reaction for removing nitrogen. (4) When the operation time of all stages was about 8h and the time schedule of each was suitable, nitrogen, phosphorus and organic subustances was removed more than 90% simultaneously.

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Experimental studies of a two-phase methane fermentation combined with a membrane separation unit were conducted to upgrade efficiency of gas production and treated water quality. The test was carried out on a pilot plant basis. The plant was constructed in a soybean processing factory and used on a continuous run basis.
The purpose of this experimental research was to obtain comparison performances of three different methane fermentation processes, 1) acidification bioreactor-methane bioreactor without a membrane separation unit, 2) acidification bioreactor-methane bioreactor-membrane unit, 3) acidification bioreactor-membrane unit-methane bioreactor.
The comparison results have demonstrated the superiority of the third process in gas production as well as in treated water quality. The experimental data on ammonium production have also clarified the degree of two-phase methane fermentation in each process. The third process has been substantiated as a two-phase methane fermentation process in the terms of solid substrate decomposition by the ammonium production analysis.

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Low strength soybean processing wastewater (BOD=1, 000mg·l^-1, VSS=690mg·l^-1) was treated, using an anaerobic two-phase membrane reactor process, in which an acidification fixed-bed reactor was combined with an ultrafiltration membrane module. A fixed-bed reactor reduced SS loading for membrane to ensure a high flux and enhanced solubilization rate with high attached soybean SS and bacteria. Studies on solubilization and acidification were conducted in the labratory scale and the continuous field tests. The following results were obtained :
1) In the batch solubilization test of soybean protein SS, under the condition of pH ranged from 5.0 to 8.3, the result showed the maximum solubilization rate constant was 0.7 d^-1 in the proximity of pH 6.0.
2) The ultrafiltration membrane concentrated both substrate soybean protein SS and bacterial SS. The permeate supplied to the methane reactor contained mainly volatile atty acids.
3) A composition analysis of SS attached on the carriers in an acidification reactor clarified 41% to 56% of total SS attached was the soybean protein SS. The field test results estimated the solubilization rate constant was 0.28 d^-1 to 0.33 d^-1.

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The evaluation of self-purification process in lakes and ponds has to be taken into consideration to control the organic pollution owing to eutrophication. In this study, the quantitative analysis of bacterial decomposition activity in eutrophicated water is achieved. From the microcosm experiments using several samples of natural watersheds, following results are obtained :
(1) Organic substrates decomposed by bacteria can be clearly classified into two groups : easily biodegradable fraction of the decomposition reduction rate constant of 0.82d^-1 and hard biodegradable fraction of 0.0070.0015d^-1.
(2) The easily biodegradable fraction is 7080 % in soluble organic matter originated from degraded plankton, while it is less than 30 % in particulate organic matter.
(3) The maximum growth rate of bacteria at 20°C is 0.19d^-1 in the case of particulate substrate, and 0.27d^-1 in the soluble substrate. Bacterial weight is estimated 310×10^-10mg as COD, and its yield is 0.5.
(4) The bacterial respiration rate R (mgO₂·l^-1·h^-1) is roughly estimated from the T-COD concentration S (mg·l^-1) and the bacterial number B(ml^-1) as the following equation : R=b×B×(S/B)^3/4, where b is 3.3×10^-5 at 20°C.

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