Kohji Kakimoto

Upgrading of anaerobic digestion of waste activated sludge by ultrasonic pretreatment

To enhance the efficiency of anaerobic digestion, we examined the effects of ultrasonic pretreatment on the solubilization of waste activated sludge (WAS) and on methane generation. Organic substances in WAS were solubilized by ultrasonic pretreatment. In the digestion with WAS pretreated by ultrasonic pretreatment for 30 min, the total quantity of generated methane increased by 64%, as compared with experimental control (non-treatment). In addition, the relationships between methane generation and concentrations of soluble protein, carbohydrate and volatile fatty acid (VFA) were also examined.

Genotoxic activities in vivo of cobaltous chloride and other metal chlorides as assayed in the Drosophila wing spot test.

A series of metal chlorides were subjected to the wing spot test of Drosophila melanogaster. In the test, larvae trans-heterozygous for the wing-hair mutations mwh and flr were orally treated at the third instar stage with a test compound and the wings were inspected at the adult stage for spots expressing phenotypes of the markers. CoCl2, MnCl2, MoCl3, NiCl2 and ZnCl2 were clearly effective in inducing spots with one or two mutant hairs (small spots). CoCl2 was clearly effective in inducing spots with three or more mutant hairs (large spots) as well. CrCl3, FeCl2 and FeCl3 were negative under the conditions used. Based on estimated frequencies of small spots induced at the LD50, the genotoxic effectiveness of the positive metal salts were ranked in a sequence of CoCl2 > ZnCl2 > MoCl3 > (MnCl2, NiCl2). Since CoCl2 did not induce large spots in the wings of the mwh/TM3 flies with a suppressed ability of mitotic crossing-over, the large spots induced by this compound in the mwh/flr system were ascertained as mutant clones due to mitotic crossing-overs.

Combined mutagenicity of cobalt(II) salt and heteroaromatic compounds in Salmonella typhimurium.

Mutagenic activities of 4-aminopyridine (4AP), 4-aminoquinoline (4AQ), 9-aminoacridine (9AA) and harman (HM) were examined by the Salmonella test system in the presence of cobalt(II) chloride (CoCl2), which itself is non-mutagenic in this system. Mutagenic activity of the mixture of 9AA and CoCl2 was found to be much higher than that of 9AA alone in strains TA1537 and TA2637. A similar enhancing phenomenon was observed in 4AQ-CoCl2 and HM-CoCl2 mixtures but not in that of 4AP-CoCl2. Judging from visible and nuclear magnetic resonance spectral data, this increased mutagenicity may be attributable to the formation of moderate to weak complexes between these chemicals and the Co(II) cation. A survey of the mutagenicity of several Co(II) complexes supported this interpretation.

Influence of hydraulic retention time on anaerobic digestion of pretreated sludge

Continuous anaerobic digestion of waste activated sludge pretreated at low temperatures below 100°C increased methane generation by 30%. pH values of the digestion mixture increased, approximately from 0.3 to 0.55 by pretreatment, although its volatile fatty acids concentration was greater than the control. An abrupt increase in propionate : acetate ratio in digestion stage (e.g. from less than 1:1 to over 3.5 :1), provided a reliable indicator for impending failure.

Reductive dechlorination of non-ortho substituted polychlorinated biphenyls by ultraviolet irradiation in alkaline 2-propanol

Abstract The photodechlorination pathways of 3,3′,4,5,5′-pentachlorobiphenyl (3,3′,4,5,5′-PentaCB) and the related lower polychlorinated biphenyl congeners irradiated at 254 nm in alkaline 2-propanol were elucidated. Steric effect is the most important factor for controlling the dechlorination pattern of these substrates. Electronic effect also influences the photoreactivity of chlorine substituents.

Effects of Pretreatment on the Solubilization and Anaerobic Digestion of Waste Activated Sludge

嫌気性消化過程の効率化を目的として, 余剰汚泥に対して超音波処理, 熱処理および凍結処理を施し, それぞれの前処理条件を詳しく検討した。各前処理により可溶性タンパク質, 炭水化物などの有機物が余剰汚泥から溶出され, その溶出量がメタン発生量に大きく関与していることがわかった。30分間超音波処理した汚泥のメタン発生量は60%以上増加し, 低温熱処理 (60℃) の場合にもメタン発生量は顕著な増加が見られ, エネルギーの面から見ても有利である。また, 前処理した余剰汚泥と種汚泥の混合比の嫌気性消化に及ぼす影響を検討した結果, 前処理した汚泥中に可溶性有機物が多量に溶出しており, 酸発酵が進んでいた。揮発性脂肪酸を蓄積しない濃度にするため, 種汚泥の割合を大きくしたほうがメタン発酵の効率はさらに向上する。

Structure-dependent variation in the mutagenic, prophage-inducing and antibacterial activities of 5-nitro-2-furamide derivatives

A comparative survey of the mutagenic, prophage-inducing and antibacterial activities of 3 structure-related series of 5-nitro-furan derivatives including 5-nitro-2-furohydrazide imide, 5-nitro-2-furamide oxime and 5-nitro-2-furohydrazide has been undertaken. Among the compounds assayed, the 5-nitro-2-furohydrazide imide series was found to be most active with regard to mutagenic and antibacterial activities against Salmonella typhimurium TA100 and prophage-inducing activity in Escherichia coli GY5027. A clear correlation was observed between the chemical structure and the mutagenic and prophage-inducing activities which were approximately correlated to the antibacterial activity.