Mercury extraction was carried out using an anaerobically stabilized sludge originated from our laboratory wastewater treatment plant. Mercury in the sludge was not directly extracted not only with KI, KBr, Na₂S₂O₃, ethylenediaminetetraacetate or cysteine solution at neutral pH, but also with 1.0 mol/l HCl. However, 20 per cent of mercury was extracted with 0.1 mol/l NaOH.
On the other hand, 55 per cent of mercury was extracted with 0.1 mol/l KI at neutral pH when the anaerobic sludge was aerated for 6 days. Treatment of the aerated sludge with hydrogen peroxide solution, followed by treatment with KI solution, resulted in 85 per cent extraction of mercury. Most of mercury remaining in the sludge could be extracted by repeated treatment with KI solution. Mercury in the anaerobic sludge could also be extracted by aerating the sludge in 0.1 mol/l KI. Further more, when the anaerobic sludge was treated with Ca (OCl)₂ at pH 8 and at pH lower than 2, 20 and 80 per cent of mercury were extracted.
Other metal ions, such as Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺, were scarcely extracted with 0.1 mol/l KI from the anaerobic sludge as well as aerobic or hydrogen peroxide treated sludges. From these results, it was clarified that KI was a specific chemical for the extraction of mercury in the sludge and that some oxidation process was essential for the effective extraction of mercury.

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An improved curcumin method has been developed using a 20% (v/v) 2-ethyl-1, 3-hexanediol, a boron complexing agent, in diisobutyl ketone as an extracting solvent. Boron in the upper, organic solvent is converted to rosocyanin complex by the addition of glacial acetic acid-curcumin solution (0.375%) and concentrated sulfuric acid in this order. The concentrate is diluted with 95% ethanol and spectrophotometrically read at 550 nm vs. ethanol. Beer's law is obeyed over the concentration range of 0.02 (cell : 5cm) -10 (cell : 1cm) mg B/l, and relative standard deviations for blank and 1 mg B/l solutions are ca. 2 and 0.9%, respectively. The improved curcumin method eliminates inconvenient time limits and the interferences of hardening agents, iron (III), fluoride and nitrate. This method with or without alkali fusion as a pretreatment was applied to the determination of boron in industrial waste water, disposal plant sewage, river water and sea water. The results obtained by this method were in good agreement with those obtained by a modified curcumin method and ICP-atomic emission spectrophotometry. When boron in a sample solution such as industrial waste water exists in the chemical form of fluoroborate, etc., the pretreatment of alkali fusion followed by this method must be carried out.

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The conditions of removal of phosphates from the different wastewater containing phosphate by addition of titanium (IV) sulfate with precipitation method were examined experimentally. As a result of experiment, it was found that about 100% phosphate was precipitated as an useful titanium phosphate from the wastewater by addition of two moles of titanium to one mole of phosphate and by adjustment of pH between 1.0 and 5.5. In the case of the wastewater containing heavy metals besides phosphate, it is desirable to set pH 1.0 as possible for removal of about 100% phosphate and for keeping the heavy metallic ions in the liquid phase successively. In the case of the wastewater containing fluoride and phosphate, it is necessary to adjust pH above 1.5 but the partial coprecipitation of fluoride is not avoidable. In the case of condenced phosphate, the phosphor was perfectly precipitated by addition of two moles of titanium to one mole of phosphor just as orthophosphates but pH must be adjusted between 1.5 and 3.0.

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Persistence of isoprothiolane, diisopropyl 1, 3-dithiolan-2-ylidenemalonate (Fuji one ^®), in river water and sea water was investigated. Isoprothiolane in water samples was quantitated and identified by a gas chromatograph equipped with an electron capture detector and a gas chromatographic-mass spectrometric technique.
Isoprothiolane residues at Chikugo river and Ariake sea sites were detected throughout the year. The maximum concentration was observed in August when it has been applied to paddy fields. After that, the concentrations reduced by degrees. However, the low levels were found in waters in January and March 1981. The detection of the chemical in this period may suggest that the appleed chemical has combined with soil surface in paddy fields and flown out gradually from these fields. The levels of isoprothiolane ranged from 0.001 to 4.2 μg/l in Ariake sea and from 0.001 to 224 μg /l in rivers and agricultural drainage.

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