報告書番号

V04030

タイトル（和文）

排水中の窒素除去に関する研究（その11） --発電所における様々な含窒素排水処理への窒素除去バイオリアクターの適用--

タイトル（英文）

Development of biological wastewater treatment system for nitrogen removal Part 11. -Practical application of nitrogen-removal bioreactor to treatment of various types of wastewater in power plants

概要 （図表や脚注は「報告書全文」に掲載しております）

発電所に存在する非定常系の窒素排水の処理への窒素除去バイオリアクターの適用について検討した。2ヶ所の石炭火力発電所より採取した6種類の非定常系の窒素排水について、成分分析を行うとともに、毒性物質の有無の指標になるアンモニア酸化菌を用いて生物処理可能かどうかを検討した。その結果、pH調整のみを行った非定常排水では、その活性は約半分に低下したが、定常系排水を模擬した排水を用いて2倍以上の希釈を行った場合、活性が大幅に向上した。さらに、バイオリアクターの実証設備を用いて、実際の非定常系の窒素排水の処理を行った結果、非定常排水をpH調整後に定常系の脱硫排水による3倍希釈により、排水中のアンモニアを亜硝酸や硝酸の蓄積無しに窒素ガスとして除去することができた。従って、窒素除去バイオリアクターは、非定常系の窒素排水にも適用可能であり、発電所の様々な窒素排水の処理に適用できると考えられる。

概要 （英文）

Various types of wastewater occur in coal power plants, within the wastewater can be found nitrogen compounds, e.g., ammonia, nitrite, and nitrate. The different types of wastewater include condensed polisher wastewater, wastewater of ammonia storage tank, and boiler start-up wastewater. The wastewater occurs at irregular intervals throughout the year. We confirmed that our nitrogen-removal bioreactor could successfully treat the irregularly occurring wastewater. We collected six kinds of wastewater from coal power plants, and analyzed about pH, EC (electric conductivity), nitrogen concentration, and so on. The six kinds of wastewater had entirely different characteristics, and they were different from those of wastewater occurring regularly in coal power plants. The effect of substances dissolved in the wastewater was observed by using Nitrosomonas europaea as an indicator of toxic substances in the wastewater. After all the wastewater was adjusted to pH of 7.5-8.0, N. europaea was incubated in the adjusted wastewater. The activity of N. europaea declined in all wastewater samples. The ammonia-oxidation rate in all the wastewater was half of that in artificial wastewater using a culture medium. However, the activity of N. europaea was recovered in wastewater diluted with the artificial wastewater. Twice dilution of the wastewater with the artificial wastewater raised the ammonia-oxidation rate of N. europaea remarkably. Further, we confirmed that a large-scale nitrogen-removal bioreactor could treat the wastewater occurring at irregular intervals in a coal power plant. After the wastewater was diluted by 1/3 with desulfurized wastewater that occurs regularly in coal power plants, the wastewater was treated by the bioreactor. Ammonia in the wastewater was removed by the bioreactor without accumulating nitrite and nitrate. The activity of the bioreactor in this study was similar to that in previous studies using artificial wastewater in a laboratory. Therefore, our bioreactor would be effective as a comprehensive system for nitrogen-removal in thermal power plants.

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