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ENERGY CONSUMPTION AND MATERIAL FLOW IN SEWAGE TREATMENT PLANT IN JAPAN
GOTO, Naohiro,HU, Hong-Ying,FUJIE, Koichi 嶺南大學校 環境問題硏究所 1999 環境硏究 Vol.19 No.1
ABSTRACT There are some measures for reducing the resource/energy consumption such as selections of optimum treatment processes and optimum operating conditions in sewage treatment facility in Japan. The objective of this study is to get information about the selections of optimum treatment processes of sewage and the optimum operation conditions. The energy consumption and material flow in the sewage treatment facilities in Japan were analyzed using statistic data. Reuse rate of treated sewage outside the treatment facilities of sewage in Japan in 1994 was 18% of domestic treated water amount. Promotion of water reuse outside facilities is necessary. Average electrical power consumption per unit volume of wastewater in sewage treatment facilities varies widely among facilities and correlates closely with facility scale. The smaller the facility scale is, the larger electrical power consumption is. Treatment volume of sewage in smaller facilities was much less than their capacity. 3.7 million t/year of the emitted dehydration cake was disposed by incineration and 0.1 million t/year was disposed by composting. Recycle rate of the cake was low. Developing new treatment process of the sludge except incineration is necessary.
Electrochemical Reductive Removal of Nitrate from Water and Wastewater
Hu, Hong-Ying,Fujie, Koichi,Goto, Naohiro 영남대학교 환경문제연구소 2000 環境硏究 Vol.20 No.1
The purpose of this study is to evaluate the possibility of some zero-valent metals such as aluminum, zinc and iron as reductants to convert nitrate in water into nitrogen gas under acidic conditions. Based on the results of comparative studies on the reduction of nitrate by metallic iron, zinc and aluminum, respectively, metallic iron was selected as a reductant of nitrate in this study. The effect of pH on the reduction rate and products of nitrate was investigated with a fixed dosage of iron powder (size: 80 mesh) of 12 mol-Fe/mol-N under acidic (pH=2-5) and aerobic conditions. The reduction of nitrate by metallic iron was a pseudo-first order reaction under our experimental conditions. The reduction rate of nitrate was increased with decreasing pH of the reaction solution, arid the pseudo-first order reaction rate constants were 0.49, 0.40, 0.75 and 0.01 1/h at pH =2, 3, 4 and 5, respectively. The reduction products of nitrate were ammonia and nitrogen, and their yields were strongly affected by pH. The yields of nitrogen was 30%, 31% and 45% at pH=3, 4 and 5, respectively, but no formation of nitrogen was found at pH=2. It was also demonstrated that the indirect reduction of nitrate by hydrogen generated from the reaction between proton and metallic iron was a major mechanism for the reduction of nitrate under the experimental conditions.