The mechanism of the luxury uptake of phosphorus by activated sludge was studied. An activated sludge process composed of an anaerobic zone followed by an aerobic zone removed almost five times more phosphorus than the conventional activated sludge process. In the anaerobic zone, most of the influent BOD was removed and orthophosphate was released. The amount of the released phosphate was found to be directly proportional to the amount of the removed BOD. For every two moles of glucose removed, one mole of orthophosphate was released; in case of acetate one mole was enough to cause the release of one mole of the phosphate. The removed glucose and acetate were stored in the sludge as glycogen and poly-j3-hydroxy-butyrate, respectively. In the aerobic zone, the released phosphate and the influent phosphorus were incorporated into the sludge and seemed to be stored as polyphosphates. Microorganisms in the anaerobic zone might utilize the polyphosphates as an energy source to incorporate BOD components and to synthesize storage compounds.

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The power economy, which is defined as the amount of BOD removed per unit power consumption, of trickling filter with plastic media was predicted and discussed under varied practical operating conditions.A mathematical model previously presented by one of the authors was used to predict the BOD removal performance in the filter, where a revised value of the rate constant was obtained and used from the test operating data in a full-scale plant.
The increase in filter depth and in recycle ratio of effluent enhances the BOD removal rate per both the unit volume and unit sectional area of the filter media, but will lead to lowering the power economy.Under normal operating conditions designated by the structural standard of community plants in Japan, sufficient quality of the effluent can be expected, but the power economy of the plants will show rather low values. In order to equalize the daily fluctuation of influent loading, the operation to maintaining constant irrigation rate to the filter media is effective, but in this operation, the decrease in the power economy will not be avoided, in comparison with the case when the equalization tank in front of the filter is applied.

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The influence of exfoliated periphyton on the pollution in the Kannogawa River flowing into the Lake Inbanuma was investigated by the use of artificial substrata.
The dominant species of microorganisms in a periphton community grown up on the artificial substrata changed seasonally, i.e., the sessile algae in summer and sphaerotilus colonies, which forms slime infestation (so-called “Mizuwata”in Japanese), in winter. The growth rate in the early growth stage of periphyton community was higher in summer than winter, but in the middle growth stage it was rather high in winter. The maximum standing crop of periphyton community was appeared in winter. The proportion of carbon and nitrogen to the attached organic matter expressed in I.L. was constant in the every growth stage, but the proportion of phosphorus was high in. the early stage.
The water quality in the Kannogawa River became worst in winter. In this season about 47 percent of the total SS load was estimated to be derived from the exfoliation of “Mizuwata”. It was also estimated that annual SS load resulted from exfoliated periphyton in the mouth of the Kannogawa River was approximately 240 ton.

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Nickel peroxide in the field of organic synthesis is known as a selective catalyst for liquid phase oxidation. Applicability of this catalyst in water or wastewater treatment is examined first by testing the adsorption characteristics of wide variety of organics.
Phenols are found to be effectively removed and then stoichiometric relation of adsorption of phenol to surface active oxygen atom on the catalyst is determined. Also from the rate of adsorption, intraparticle diffusion kinetics is found to be controlled by pore diffusion.
Regeneration of spent catalyst by sodium hypochlorite as well as cyclic use of nickel peroxide is examined and found practicable.

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Growth characteristics of Chlorella sp. isolated from a sedimentation tank in glycine, glucose and inorganic medium and also in peptone medium in association with B. megaterium were discussed.
Chlorella sp. utilized glycine phototrophycally and specific growth rate (μ) was 3.35 day^-1 (25°C). The isolate also utilized small amount of glycine heterotrophycally (under dark and the supply of air) and specific growth rate (μ) was 2.76 day^-1. The isolate utilized glucose heterotrophycally (μ= 2.70 day^-1). Under the supply of CO₂ enriched air to the inorganic medium, specific growth rate of 3.30 day was obtained at more than 0.6% CO₂ concentration.
Although the isolate showed a little growth in 0.5% peptone medium, it grew promptly when it was incubated in association with B. megaterium. This symbiotical growth took place under light and oxygen limited conditions (μ=4.50 day^-1, 2°C). No growth of Chlorella sp. was observed under an aerobic condition. Growth rate of the isolate was accelerated with an increase of temperature and reached to the maximum μ of 8.0 day^-1 at 36°C. Rapid growth was still observed at 42°C. But, this high growth rate continued only for 12 hrs. In 0.1% glycine medium, the maximum growth rate without bacteria was observed at 30°C., and growth was completely ceased above 40°C. Carbon analysis before and after incubation indicated that organic carbon degraded by the bacterium quantitatively transferred to the biomass. This symbiotical growth was also observed in simple organic medium in which B. megaterium could grow.
From these results, it was assumed that the symbiosis observed between B. megaterium and Chlorella sp. fundamentaly consisted of interchange of CO₂ and O₂. But, high growth rate observed in symbiosis might indicate the existence of more complicated mechanisms supporting each other.

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