In order to explain the mechanism of phosphate release from lake sediments under aerobic conditions, the behavior of Fe (II) and phosphate added to yeast extract solutions under bacterial growth was examined, which is to imitate the situation where Fe (II) -phosphate is released from anaerobic sediments to aerobic overlying waters.
When Fe (II) in Fe₃ (PO₄) ₂ was added to yeast extract solutions under bacterial growth, it was oxidized to Fe (III). Althouth a part of Fe (III) precipitated as Fe (OH) ₃, the rest remained in stably soluble form by complexing with dissolved organic ligands contained in yeast extract solutions. On the other hand the most part of Fe (II) in Fe₃ (PO₄) ₂ added to distilled water precipitated immediately as Fe (OH) ₃.
Phosphate added with Fe (II) to yeast extract solutions was adsorbed to precipitated Fe (OH) ₃ in the ratio of 0.41 0.46 mol phosphate to 1 mol Fe (OH) ₃. Phosphate released with Fe (II) from anaerobic sediments to aerobic overlying waters was supposed to remain soluble except the portion of adsorbing to Fe (OH) ₃ in the above ratio.

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The organic water pollution of streams and lakes has been usually discussed from the different view point, i.e. in running waters it has been discussed from the view point of saprobic system, in standing waters from that of trophic system, as is generally known.
Such the difference in measure to determine the degree of water pollution between the two make the composite discussion difficult.
Recently, a numerical index to organic pollution of running waters (Diatom Assemblage Index -DAI_po) has been developped based on epilithic diatom assemblages.
In this research, the applicability of DAI_po to pollution of standing waters was investigated using 100 attached algal community samples collected from dammed lakes, irrigation ponds and fish culture ponds, and 246 diatom taxa occurred at 100 sampling sites were able to be classified into three ecological groups, Saprophilous, Eurysaprobic and Saproxenous based on their tolerance index without a considerable alternation in the ecological group to which the taxon belongs, compared with the former result obtained from running waters.
In attached diatom assemblages of standing waters, relative abundance of taxa belonging to each ecological group varies in proportion to increase of DAI_po value in the same manner as shown in running waters.
From the facts, we may conclude that DAI_po is useful not only to running waters, but also to standing waters, as a common index to organic pollution degree.

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In order to improve the dewatering of sludge using cationic polyelectrolytes, the development of an analytical system for determining the residual concentration of polyelectrolytes in the interstitial liquid of the flocculated sludge was desired. The effect of salts and turbidity on the determination of cationic polyelectrolytes by colloid titration was studied using a two-wavelength photometric cell.
The results obtained were as follows :
1) The effect of salts was different for polyelectrolytes with differing cationic charge densities. The effect decreased with increasing charge density of the polyelectrolyte.
In order to maintain an accuracy up to ±5% for concentrations of higher charge density polyelectrolytes (0 '0.2meq E1^-1), the ionic strength had to be lower than 0.04.
The effect of salts greatly increased with higher concentrations of the lower charge density polyelectrolytes. In order to maintain the same accuracy of the higher charge density polyelectrolytes for the lower charge density polyelectrolytes, the concentration of the lower charge density polyelectrolytes had to be kept under 0.02 meq ·l^-1.
2) The effect of turbidity can be disregarded between 0 and 150 degree of turbidity unit.

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Effects of inorganic salts, especially of inorganic anions, were examined on the elution profiles of organic matter in sewage treated water on Sephadex G-15 with water as the eluent.
The results of this study have led to the following conclusions.
(1) The effects of inorganic salts on the gel chromatographic behavior of organic substances were principally the same as in the salt boundary technique proposed by Posner, although the salt boundaries more than one were observed in this work.
(2) The effects of anions are decisive in the elution behavior of organic substances.
(3) The principal role of inorganic salts is presumably the suppression of charge induced exclusion.
(4) Whether the sample contains inorganic salts or not, the chromatogram of organic matter with water as sole eluent may be of limited value to obtain information about the molecular-weight distribution of natural organics in aquatic environment.
(5) Even apart from the subject of the moleculer-weight distribution, the information of coexisting inorganic salts is, at least, inevitable for evaluating the quality of natural and waste on the basis of the organics.

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