Abstract
Intermittently aerated activated sludge system has the flexibility against variations of inflow, because aerobic and anaerobic periods can be determined in time base. And also it can be applied to existing activated sludge processes by minor structual changes. This paper show the design and control strategies of intermittently aerated activated sludge process, which give the simultaneous and stable removal of nitrogen and phosphorus.
In a reconstructed extended aeration plant (design capacity 625m3·d-1), under the condition of F/M ratio 0.022-0.037 (kgBOD5·kg-1MLSS) and N/M ratio 0.0064-0.0092 (kgT-N·kg-1MLSS), the effluent quality was kept less than T-N 5mg·l-1 and T-P 1mg·l-1 during a year. In a more advanced control period, the average values of total nitrogen and total phosphorus were 1.8mg·l-1 and 0.2mg·l-1. Dynamics of nitrogen and phosphorus in the reaction basin along the flow are shown in the paper.
It is shown that two stage structure of reaction basin is primarily important, and next the control strategies which guarantee the first basin to pass through a deep anoxic condition and the last basin to be kept in an oxic condition is necessary.
