報告書番号

U91002

タイトル（和文）

高能率魚類生産のための水質浄化技術の開発７．飼育水中の硝酸イオンの除去と脱窒菌の活性発現要因

タイトル（英文）

DEVELOPMENT OF WATER-PURIFICATION TECHNOLOGIES FOR INTENSIVE FISH CULTURE 7.REMOVAL OF NITRATE ACCUMULATING IN CULTURE SEAWATER AND FACTORS AFFECTING DENITRIFICATION OF MARINE DENITRIFLYING BACTERIA

概要 （図表や脚注は「報告書全文」に掲載しております）

微生物による魚類飼育水中の硝酸イオンの除去方法（脱窒）について検討した。生物膜法により脱窒を行なう場合，活性は砂濾材＞繊維状のプラスチック濾材＞板状のプラスチック濾材の順で高かった。また，有用な脱窒菌を濾材に接種することで，濾過槽の脱窒活性が早く，かつ高く発現することが分かった。脱窒を行うための条件としては，以下のことが明らかとなった。（１）脱窒活性は硝酸イオン濃度が１００ｐｍ－Ｎ程度で飽和した。（２）脱窒のエネルギー源として適切な有機物の種類は菌株により異なったが，発現する活性が比較的高いことや価格等からグルコースまたはサッカロースの利用が適当と判断された。（３）脱窒は溶存酸素温度の増加によって大きく低下し，高い活性の維持のためには嫌気度を高める必要があった。しかし，ＤＯ飽和度３０％位でも活性を保ちうる菌株も存在しており，これら菌株を用いればＤＯを比較的高くしたままでも脱窒が

概要 （英文）

THIS STUDY SELECTED USEFUL FILTER MEDIA FOR A DENITRIFYING BIOLOGICAL FILTER AND EXAMINED THE EFFECT OF INOCULATIONOF MARINE DENITRIFYING BACTERIA ON FRESH FILTER MEDIA. ALSO,THE EFFECTS OF FACTORS SUCH AS SPECIES AND CONCENTRATION OF ORGANIC SUBSTANCE,NO3--N CONCENTRATION AND DISSOLVED OXYGEN (DO) CONCENTRATION ON THE DENITRIFYING ACTIVITIES OF THE MARINE BACTERIA WERE STUDIED. THE HIGHEST DENITRIFYING ACTIVITY WAS OBTAINED IN COARSE-SAND FILTER (APPROXIMATE DIAMETER 3 6MM). A FINE VINYLIDENE CHLORIDE FILTER WAS NEXT BEST. HONEYCOMB PLASTIC TUBE SHOWED THE LOWEST ACTIVITY AMONG THE THREE FILTER MEDIA TESTED. ACTIVITY WAS SHOWN FROM THE EARLY STAGES AND HIGHER ACTIVITIES WERE OBTAINED BY INOCULATION OF CULTURED DENITRIFYING BACTERIA ON THE FILTER MEDIA. ACTIVITIES INCREASED WITH INCREASING NO3--N CONCENTRATION INTHE SEAWATER UP TO 100 MG-N/1 BUT THEN WERE ALMOST CONSTANT FROM 100 TO 1000 MG-N/1. ACTIVITIES DIFFERED DEPENDING ON THE SPECIES OF ORGANIC SUBSTANCE SUCH AS GLUCOSE,SACCHAROSE,PEPTONE, GLUTAMIC ACID AND METHANOL IN EACH TESTED STRAIN. GLUCOSE AND SACCHAROSE WERE CONSIDERED TO BE BETTER ENERGY SOURCES FOR DENITRIFICATION FROM THE VIEW POINT OF ACTIVITY LEVEL AND COST. ALSO,ADDITION OF 1.2 MG-C OF ORGANIC SUBSTANCE WAS NECESSARY TO REMOVE 1 MG-N. ACTIVITIES DECREASED AS THE DISSOLVED OXYGEN (DO) INCREASED. IT WAS NECESSARY TO MAINTAIN A LOWER DO LEVEL TO DEMONSTRATE EFFICIENT DENITRIFYING ACTIVITIES. BUT ONE STRAIN MAINTAINED DENITRIFYING ACTIVITY AT COMPARATIVELY HIGHER DO LEVELS. THIS STRAIN IS CONSIDERED USEFUL FOR REMOVING NITRATE FROM FISH CULTURE WATER.

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