Abstract
In the batch operation of laboratory scale anaerobic-aerobic activated sludge (AS) process, two operating conditions were compared. In the case of “Supernatant Withdraw Operation (SWO)”-the normal operation of AS, supernatant was withdrawn as effluent. In the case of “ML Withdraw Operation (MWO)”-the normal operation of pure culture, only small amount of mixed liquor was withdrawn. Phosphorus removal reduced after the change of operating conditions from SWO to MWO. However, after ninety days of MWO, recovery of enhanced phosphorus removal was observed for a month. It was unable to maintain this phosphorus removal for longer period under MWO.
In the enhanced phosphorus removal ASs, 18 to 50% of total isolates were identified as Acinetobacter calcoaceticus var. lwoffi by the API20E System, while only one isolate was identified by the API20NE System. No isolate of low phosphorus removal AS was identified as Acinetobacter by either System. One of the bacteria playing a functional role on enhanced phosphorus removal may, therefore, be identified as Acinetobacter calcoaceticus var, lwoffi by the API20E System, but not by the API20NE System.
The isolates which could not be identified to the genus level was 52% of the total isolates. The cluster analyses were applied to classify all these isolates effectively. The enhanced and low phosphorus removal ASs were clearly distinguished by the Ward method.
