Activated sludge process

Japanese: 活性汚泥法 - かっせいおでいほう（英語表記）activated sludge process

This is one of the biological oxidation methods for sewage. When sewage is aerated and stirred in an aeration tank together with activated sludge (a group of bacteria that oxidize sewage under aerobic conditions) and the biochemical oxygen demand (BOD) is almost met, colloidal or dissolved substances in the sewage precipitate or are adsorbed by the activated sludge, turning the water into clean water. In general, urban sewage is purified in 4 to 8 hours. After the activated sludge has performed its purification function, it is separated by settling from the sewage to be treated, and is discarded as necessary or sent back to the main treatment process. This method is more efficient than other sewage purification methods, such as the trickling filter method, and has the advantage of not causing odors or breeding flies.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

下水の生物学的酸化法の一つ。下水を活性汚泥 (好気的条件で下水を酸化する細菌集団) とともに曝気槽で曝気，攪拌し，生物化学的酸素要求量 BODをほぼ満足させるようにすると，下水中のコロイド状ないしは溶解した物質が沈殿したり，活性汚泥に吸着されてきれいな水になる。一般都市下水では4～8時間で浄化される。活性汚泥は浄化作用を行なったのち，次々と処理対象物である下水から沈殿によって分離され，必要に応じて廃棄され，あるいは再び本処理過程へ返送される。この方法は他の下水浄化法，たとえば散水ろ床法に比べて効率がよく，臭気，ハエの発生をみない長所がある。

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