Shigeki Nakajima

Relationships between water quality, morphological factors in river basins, the diversity index and the biotic index

Abstract The relationships among water quality, the morphological factors in river basins, the Diversity Index, and the Pollution Index were analyzed by the principal component, using the data obtained from the rivers in Kumamoto Prefecture from 1984 through 1988. The value of the Pollution Index, which was used as a biotic index, correlates with both water quality and morphological factors.

Comparative performance studies on model hoppered peripheral feed and center feed clarifiers

Abstract The intractability of the full equations of motion in the domain of clarification has resulted in the development of empirical design and performance criteria. This state of affairs has led to a proliferation of clarifier types; each with in many cases, unsubstantiated claims of superiority of performance. The objective of this work was to attempt to use a coherent methodology coupled with objective criteria in the development of appropriate final clarifier configurations for planned oxidation ditch plants that are envisaged to serve small communities. The paper reports the results of the first phase of on‐going research and development work on the not so well studied hoppered final clarifiers. In the current phase of the work, physical hydraulic scale models were used. It is concluded that in terms of hydraulic detention efficiency, the peripheral feed clarifier, as modelled, is relatively more quiescent (average coefficient of clarifier performance 0.29) than the center feed clarifier (average ...

A Fundamental Study of the Sulfate Movement in the Forest Soils.

Sulfate leaching was studied in the laboratory in undistributed Ando soil cores comprising I A, I B, and II A horizons that were taken in a Japanese cedar forest. The soil cores were watered with 0.4 me.l-1 sulfuric acid solution having pH 3.0. The sulfate concentration of the leachate remained at about 0.05 me.l-1 at pH 4.1 to 4.2, but after 15l sulfuric acid solution was applied, SO42- leaching was accelerated at pH 3.9 to 4.0. The stability diagram showed a better fit with gibbsite. In the I A horizon, which did not accumulate SO42, the soil pH was 3.1. SO42- accumulation had occurred in both the I B and II A horizons. The adsorption maximum was about 4.0 me · 0.1 kg-1.

Simultaneous removal of fluoride and phosphate by fluoroapatite crystallization with sintering pellets of activated sludge ash

Abstract A method of fluorides treatment by fluoroapatite crystallization is described. By using this method, it was possible to remove simultaneously fluoride and phosphate. For the purpose of recycle use of waste activated sludge, sintering pellets of sludge ash was used as a seed for crystallization. The kinetic formulation have been studied by batch experiments. The effect of operating conditions on reaction constant was discussed. The crystallization reaction follows a second oder kinetic law. The reaction constant was depended on initial pH, saturation index Sl and ambient temperature. The reaction constant were proportional to both the 1.7 power of initial Sl and the 4.8 power of the initial pH. Free activated energy was 10.13KJ/mol for fluoride.

Pollution evaluation of the river in Aso caldera area by the methods of moltivariate analysis

阿蘇カルデラ内火山流域河川を対象に, 1984年12月, 1985年4月, 8月, 11月に実施した流量, 水質, 底生動物の調査結果を用いて, 多変量解析法である主成分分析や重回帰分析を行ない阿蘇火山流域河川の評価を行った。水質の主成分分析の結果, 第一主成分Z1 (16I, 7S) およびZ1 (9I, 7S) に火山流域河川の水質特性を示すものが抽出された。次に最下流調査地点に対する火山性汚濁評価を, 第一主成分得点差と流量比との積 (火山性汚濁得点Pii=1～6) により行った結果, ホ場整備の際に黄鉄鉱地帯に埋設された暗きょが大きな汚濁化作用を有することが示された。底生生物と水質の重回帰分析の結果, 生物相に最も影響を与える水質項目はF-であった。また, 水質の第一主成分Z1 (9I, 10S) と生物の群集類似度DI (N) の間にはDI (N) =1.888e-0.192Ziの関係が示され, 火山性汚濁が進行すると底生動物の生息が阻害される水環境になることがわかった。