Abstract
In order to remove phosphorus from domestic wastewater, enhanced biological phosphorus removal (EBPR) and the activated sludge process with coagulant addition have been widely used. According to the performance of phosphorus removal in actual existing facilities, it is considered possible to reduce the amount of coagulant added to the aeration tank by combining of the two processes. Therefore the dynamics of phosphorus and coagulants were investigated by examining three existing domestic wastewater treatment facilities. EBPR took place unintentionally in these facilities because of their denitrification operations. The unintentional EBPR was unstable and its performance was poor when denitrification was incomplete. An addition of coagulants to the unintentional EBPR facilities stabilized the performance. The coagulants moved to the activated sludge immediately after their addition. The content of the coagulants in the activated sludge decreased exponentially with a constant rate of 1/SRT after the ceasing of addition. The performacne of phosphorus removal continued to be high and stable while the coagulant content was remained high. Maintaining a high coagulant content of the sludge is effective to keep the performance of phosphorus removal. This indicated a new method of reducing the amount of coagulant addition.
