The day-to-day variability of the 14 Exposition visitors has been seasonally adjusted by U.S. Bureau of Census Method II. X-ll. Trend-cycle was classified into five patterns, that is the pattern of constant increasing, having peak in the first stage, in the middle stage, in the last stage, and expectation. There found four distinction of a day of the week factor, that is small fluctuation, large fluctuation, Sunday's increasing ratio, and Saturday's high ratio. On large scale expositions the peak become in the last stage and a day of the week factor fluctuates small, besides on small scale expositions no peak was found and the high ratio of visitors usually expected on Sunday.

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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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This work was primarily undertaken to reveal the water-bloom formation processes in Lake Kasumigaura which is well known as a hyper-eutrophic lake.
Growth characteristics of Microcystis isolated from the water-bloom in Lake Kasumigaura were studied. The optimum temperature for the growth of Microcystis was between 30 and 35°C, whereas the appropriate range of light intensity for the growth was estimated to be from 500 to 1000 lux. Yields on conversion from phosphorus or nitrogen to biomass (dry weight) of Microcystis were 950 (mg cell/mg P) and 55 (mg cell/mg N), respectively. Large variations of intracellular phosphorus concentration during batch culture were observed. Rate of phosphorus uptake for the cells depended only on the intracellular phosphorus concentration. Microcystis, in addition, was cultivated in a highly controllable microcosm, and accumulated on the water surface as is observed in Lake Kasumigaura.
Using M. aeruginosa and Selenastrum capricornutum as test algae, algal growth potential (AGP) in Lake Kasumigaura was determined. For the water samples of the center of Lake Kasumigaura, the addition of nitrogen compound enhanced AGP values.

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Simultaneous adsorption removal of NH₄⁺ ion and PO₄^3-ion was experimentally investigated with a bench scale apparatus of an adsorption-membrance separation hybrid system using the mixed adsorbent of nature zeolite and activated alumina.
Using an adsorbent only, even the membrane permeation did not changed in the presence of both NH₄⁺ ion and PO₄^3-ion. However, the membrane permeation and removal efficiency of each ions were strongly influenced by the kind of adsorbents and its combination. Using the mixed adsorbent of nature zeolite and activated alumina, in particular, the adsorption rate was fast and the adsorption ion concentration rapidly reached up to the equilibrium concentration of each ions.
The adsorption-membrance separation hybrid system reported in this paper is useful for the simultaneous adsorption removal of nitrogen and phosphorus in water.

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Microcystisの異常発生機構を明らかにするため, MicrocystisおよびChlamydomonas, Synedraの増殖特性を検討すると共に, マイクロコズムを用いて2者培養を行い, Microcystisの異常発生のシミュレーション実験とばっ気による制御実験を行った。MicrocystisとChlamydomonasとでは, 20℃, 30℃では低照度下ではMicrocystisのμが, また高照度下ではChlamydomonasのμが大きかった。このため, 水中照度の鉛直方向の減衰が著しい場合, Microcystisのμが相対的に大きくなり, 異常発生に至りやすいと推定された。MicrocystisとSynedraの場合, 30℃ではMicrocystisのμがSynedraを上回るため, Microcystisが優占になった。またマイクロコズム内の水全体をばっ気することによってMicrocystisへの遷移が遅れたり, 優占種にならなかったことから, 湖水のばっ気, もしくは人為的循環には, Microcystisの異常発生を遅延する効果があると推定された。

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精密膜表面に粒子径約14μmの珪藻土によるプレコート層を形成し, ファウリング抑制効果を検討した. 対象水として0.4～0.8μmの懸濁粒子が主体である河川水と貯水池水を用い, 珪藻土をそのまま, あるいはポリ塩化アルミニウム (PAC) で被膜した後, プレコート剤 (ろ過助剤) として用いた. その結果, 珪藻土をそのまま用いたプレコートろ過ではファウリング抑制効果が得られなかったが, 珪藻土をPAC被膜することによって顕著なファウリング抑制効果を得ることができた. PAC被膜した珪藻土を用いたプレコートろ過におけるファウリング抑制は, 珪藻土表面がPACで被膜され, もともと負電荷を持つ珪藻土が正の表面電荷を持ったことによって負に荷電した水中の懸濁粒子を電気的に捕捉し, 膜表面への到達を抑制できたことによると推定された

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The purpose of this study is to clarify the effects of submerged breakwater on an artificial tidal flat ecosystem. The studied tidal flat ecosystem is composed of three zones, that is, low-, high-and no-submerged-breakwater zones.
The frequencies of shear stress being higher than the critical value (0.1N m^-2) for silt transport in the low- and high-submerged-breakwater zones were lower than that in the no-submerged-breakwater zone. The silt and organic carbon contents in the low-and high-submerged-breakwater zones were higher than those in the no-submerged-breakwater zone. The slopes, reduction zone and permeability of sediment in the submerged breakwater zones were almost the same as those in natural tidal flats at Hiroshima Bay. However, the no-submerged-breakwater zone showed a sharper slope. The total population density of macrobenthos in the low-and high-submerged-breakwater zones were about twice as high as that in the no-submerged-breakwater zone. The dominant macrobenthic species in the submerged breakwater zones were Ceratonereis erthraeensis and Mediomastus sp., which are common in natural tidal flats at Hiroshima Bay. These results suggest that the construction of submerged breakwaters could change both the physiochemical and biological properties of artificial tidal flats similarly to those of natural tidal flats at Hiroshima Bay.

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本研究は，瀬戸内海において製鋼スラグによって人工的に創出した岩礁性藻場生育基盤による二酸化炭素吸収の効果を確認するため，海藻着生などの炭素吸収について検討することを目的とした。人工岩礁性藻場生育基盤は2013年2月～2018年2月に計4回施工を行い，合計面積は36,500 m²であった。岩礁性藻場生育基盤は，創出後16～40カ月まで海藻着生湿重量は季節的な変化をしながら1,251～2,916 g·cm⁻²まで増加した。岩礁性藻場生育基盤創出前の1981～2012年における岸側の砂泥域の平均藻場面積は1,259 m²であったが，創出後に流れや波浪の抑制によって2014～2020年における平均藻場面積は5,934 m²と4.7倍に拡大し，海草の株密度も増加した。人工岩礁性藻場生育基盤創出前の2012年では砂泥性藻場による年間炭素吸収量は6 kgCであったが，創出後の2015年には創出岩礁性藻場面積は11,528 m²，増加砂泥性藻場面積は3,919 m²となり，増加炭素吸収量は1,476 kgC（創出岩礁域824 kgC, 砂泥域652 kgC）と増加した。2018年には，創出岩礁性藻場面積は36,540 m²，増加砂泥性藻場面積は5,068 m²となり，増加炭素吸収量は4,658 kgC（創出岩礁域3,200 kgC, 砂泥域1,458 kgC）と更に増加した。製鋼スラグによる人工岩礁性藻場生育基盤の創出によって二酸化炭素吸収の効果が定量化できた。

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Changes in water quality with degradation of gray water under anaerobic and aerobic condition were investigated by batch incubation at 20°C. Degradation rate of dissolved organic carbon (DOC) in gray water under anaerobic condition was smaller than that under aerobic condition even with inoculation of anaerobic bacteria. Concentration of dissolved nitrogen (D-N), ammonium nitrogen (NH₄-N), nitrate⁺nitrite (NO_x-N) and dissolved phosphorus (D-P) in gray water with inoculation under aerobic condition decreased clearly in six hours from the start of incubation. Concentration of DOC, D-N, NH₄-N and D-P in gray water without filtration and inoculation under aerobic condition decreased gradually in a day from the start of incubation. Decrease rates of DOC and total organic carbon (TOC) were expressed by first order equcation. Decrease rate of D-N was expressed by Monod equcation. Decrease rate of NO_x-N was influenced by its own concentration and DO concentration. The decrease rate of NO_x-N was suppressed under high DO concentration. Relationship between decrease rate of D-P and concentration of D-P was not clear.

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The continuous monitoring of water quality at Nomura dam is carried out with a water-quality profiling system(YSI Inc.). It is equiped near the aerator and the effect of aeration on water quality is investigated. The sampling time and depth intervals are 2 hour and 1 m, respectively. The measuring items are water temperature, pH, turbidity, DO, Chl and the number of Blue-Green Alga per unit volume. Microcystis aeruginosa migrates up and down diurnally. Namely, it can be found near the water surface early in the morning and at midday exists at about 5m depth.

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In this paper, we report such results of time studies about hospitals, parking places and railway stations as follows. 1. a. At Osaka Univ. Hospital, the number of patients entering this hospital is 1, 929. The peak of arrival is between 9 : 30 and 9 : 35 and the ratio of concentration in 30min. is about 20%. Here, the ratio of concentration is proportion of number of persons entering in 30min. to total accumulation in one day. b. At Osaka City Univ. Hospital, the number of patients entering this hospital is 658. The ratio of concentration in 30min. is about 26%. 2. a. At Nagahori parking place in Osaka, the number of cars entering this parking place is about 1, 500. The ratio of concentration in 60min. is about 13%. b. At Azuchimachi parking place in Osaka, the number of cars entering this parking place is about 500. The ratio of concentration in 60min. is about 14%. 3. a. At. Osaka City underground railway stations, the ratio of concentration in 60min. is about 25%. b. At Japan national railway stations, the ratio of concentration in 60% is about 17%.

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The objective of this study is to determine aerobic and anaerobic biodegradation rates of hexadecane (HEX), phenanthrene (PHE), and anthracene (ANT) using estuarine sediments of Tama River in Tokyo and to estimate degradation potentials of these petroleum hydrocarbons in estuarine sediment of Tama River. Known amounts of these petroleum hydrocarbons were added to sediment slurry prepared by mixing estuarine sediment with bottom water in Tama River (sediment : water=1 : 1 v/v). Sediment slurry was incubated by reciprocal shaking in aerobic and anaerobic condition at 20°C. After sediment slurry was sampled periodically and extracted with ethyl acetate, these petroleum hydrocarbons in sediment were determined by gas chromatography with FID. In aerobic incubation series, the cells number of total heterotrophic bacteria and HEX-, PHE-, or ANT-utilizing bacteria in sediment slurry was determined. Aerobic biodegradation rates of HEX, PHE, and ANT in sediment slurry ranged from 40 μg·g^-1 dry sediment·day^-1 to 70μg·g^-1 dry sediment·day^-1. Anaerobic biodegradation rates of HEX were 5-8 μg·g^-1 dry sediment·day^-1. But, biodegradation of PHE and ANT was not observed during the two-month incubation period. Aerobic degradation of HEX was not affected by existence of PHE or ANT. The mumber of HEX-, PHE- or ANT-utilizing bacteria was 5-10 percentage of total heterotrophic bacteria in estuarine sediment. Biodegradation potentials of petroleum hydrocarbons in estuarine sediment of Tama River calculated from biomass of the utilizing bacteria in estuarine sediment and biodegradation rate per cell of utilizing bacteria in the period of constant biodegradation being observed were 1.0-3.5μg·g^-1 dry sediment·dry^-1 of HEX and 1.2×10^-2-4.2×10^-2μg·g^-1 day sediment·day^-1 of PHE or ANT.

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In this study, a new method has been developed for the direct removal of algae from eutrophic water. A pair of electrodes consisted of copper (or aluminum) plate cathode and aluminum plate anode was set in an eutrophic water suspended algae, and then direct current was applied. The applied current and concentration of algae were varied in the range of 10-180 mA and 1.00X10⁸-9.96X10⁸cells·ml^-1, respectively.
As algae have negative charge in water, they migrated to the anode and then adhered on its surface. The adhered algae were easily detached from the anode and removed from the water at high efficiency. The accumulation rate of algae on the surface of anode was increased with increasing applied electric current and initial concentration of algae.

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火災発生時に地上への直接避難が難しい場合，避難者が建物内の安全区画に滞留し，一時的あるいは鎮火まで避難籠城しなければならない状況を想定し，このような場合，安全区画に要求される対人距離や面積を心理的な観点から明らかにすることを目的として，実測および実験を行った。心理的アンケートを用いて，被験者1人に対して，相手が1人及び8人の場合，心理的な圧迫感を受けないために必要な面積として，各々，2．6及び2．9m²／人を得た。また，実測により，電車待ち行列では，最密状態の場合，夏季及び冬季で，各々1．6及び1．9人／m，信号待ちの群集密度では，夏季及び冬季について，各々1．5及び1．6人／m²を得た。以上。安全区画内避難における人口密度の問題に焦点を絞り，計画上の知見を示した。
（オンラインのみ掲載）

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Laboratory scale rotating biological contactors were operated with synthetic wastewater to study the effects of the daily fluctuation of hydraulic and/or organic loadings as observed in wastewater treatment plants for small communities on the removal of organic substrates.
The following results were obtained.
1) Daily average effluent COD values observed in operations with varying inflow rate and strength of wastewater (variable loading) were higher than those of constant loading (no daily fluctuation of inflow rate nor strength of wastewater) with equivalent daily BOD and hydraulic loadings.
2) Little fluctuation in effluent COD was noted by the fluctuation of influent COD concentration under smaller constant flow rate, whereas the fluctuation increased with the increase in hydraulic loading.
3) Attached biomass observed in operations with variable loadings were smaller than those observed in constant loading operations with equivalent daily BOD and hydraulic loadings to high loading period of variable loading. This fact, i.e. the shortage of attached biomass, seemed to result in the higher effluent COD values during high loading period in variable loading operations and, as a consequence, the higher daily average effluent COD values.

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