The study concerns the photodecomposition of volatile chlorohydrocarbons (VCs) with hydroxyl radical which derives from the photo-dissociation of Fe (III)-monohydroxy complex at acidic pH.
The initial decomposition rate of chloroform (CF) with irradiation of a 500 W high-pressure mercury lamp at pH : 3.0 was smaller than those of trichloroethylene (TCE) and tetrachloroethylene (PCE). However, the conversion of organic chlorine of CF to chloride ion was larger than those of TCE and PCE. The generation rates of ferrous ion differed greatly, depending upon chlorohydrocarbons.
The initial decomposition rates of PCE with irradiation of monochromatic light (313nm) were measured at pH : 3.0. The results were in good agreement with the kinetic model that assumed the steady-state concentration of hydroxyl radicals. The intermediate identified in the photodecomposition of PCE other than chloride ion was trichloroacetic acid (TCAA).

抄録全体を表示

The floatation of a primary sewage sludge was studied experimentally. Micro gas bubbles in sewage sludge decrease the efficiency of gravity settling. In the present paper, the buoyancy force of these bubbles were utilized for thickening. To promote the gas generation, sludges were continuously heated during the floatation.
The results obtained by laboratry experiments are as follows ; (A) at 40°C heat treatment, the floatation process completes for about 20 hours and the value of pH increased during the floatation. (B) in case of 60°C, floatation time is sufficient with 6 hours and pH decreased. (C) In both cases, primary sewage sludge with 95% of intial moisture content was thickened to 90%. (D) In case of 50°C, floatation speed and thickening effect were lower than those of both 40°C and 60°C.
Pilot plant experiments also showed the similar results as those of laboratory experiments. In addition, floatation thickened sludges were compressed with a belt press. Without using any additives, the sludge was dewatered to 61% moisture content. Thus. thermally treated primary sludge exhibited so high dewaterbility.

抄録全体を表示

The effect of EDTA on the total cyanide distillation (JIS K 0102 38) has been studied. Cyanide ion could be recovered quantitatively by distillation from most of the cyanide compounds without EDTA. However some compounds, e.g., potassium hexacyanocobaltate (III), did not give good cyanide ion recovery either with or without EDTA. For ferri (ferro) cyanide in the presence of a large excess of some metal ions, EDTA was effective for the quantitative distillation of cyanide. It could therefore be presumed that EDTA prevented the formation of insoluble ferri (ferro) cyanide by the chelate formation with the metal ions added and did not dissociate the ferri (ferro) cyanide ion. The reagents used in Standard Methods (APHA) showed almost the same effects on the cyanide distillation as those given by the reagents used in the JIS method. For some actual waste waters, the JIS method (EDTA involved) gave the higher analytical values of cyanide than Standard Methods (EDTA not involved). This suggested the participation of EDTA in the formation reaction of cyanide ion.

抄録全体を表示

Chemical contamination in river, ground water and sea was investigated from 1988 to 1992. Water and sediment samples collected in Tokyo area were analyzed by GC/MS, GC and HPLC. Over 40 chemicals were detected in water and/or sediment. Several distribution patterns of chemicals were observed in water and sediment media. In ground water, high levels of volatile chlorinated hydrocarbons were detected. Water and sediment samples from industrial area contained higher concentrations of chemicals than those from urban area. Pesticides and combustion products were observed in wide area. Contamination levels of each chemical in water and sediment samples indicated to be dependent on the physico-chemical property as well as the emission amount.

抄録全体を表示

In this report, the performance of up-flow charcoal bed contact treatment plant was experimentally investigated to determine the design-operating parameters and its proper maintenance method to ensure effective purification. Some improvements (e.g., in flow direction, and lower part of tank) have been made on this plant. In this experimental plant, polluted water runs through charcoal bed in the upward direction, which is different from conventional gravel bed contact treatment plant, where contaminated water runs in the horizontal direction. Water-purification test, biological test, and a test on maintenance methods were conducted, with using river water and secondarily treated domestic waste water.
Removal efficiencies of BOD, SS, T-N and T-P were approximately 80%, 90%, 30% and 40%, respectively, at about 30-40 minutes of contact time. Also, it became apparent that the SS removal in influent part of the plant was expected to allow long-term purification without the rapid development of clogging in charcoal bed. The aeration-washing of the charcoal bed with diffuser avoided the deterioration of treatment performance due to the clogging. Therefore, up -flow charcoal bed contactpurification seemed to have a advantage to treat river water polluted.

抄録全体を表示