Abstract
Activated sludge process with submerged membrane separation is a high-efficient and energy-saving wastewater treatment process. Interest has been now growing particularly in a single-reactor membrane-separation system, because the system component is simple and nitrogen, which is a cause substance of the eutrophication problem, can be efficiently removed by operating the reactor with intermittent aeration. However, operational factors influencing on nitrogen removal and the permeate flux in this system have not been clarified yet. This study was conducted to investigate the effects of aeration cycle and sludge load on these performances by continuous operation of the reactors. First, the influence of aeration cycle was investigated. Reactors were operated under four different conditions ofaeration cycle. As the results, a cycle of 30 minutes aeration and 30 minutes non-aeration was most effective in both nitrogen removal and the maintenance of permeate flux. Next, the influence of sludge load was investigated. Operation with sludge drawing was compared with the operation without sludge drawing under high volumetric load conditions. It was revealed that the operation without sludge drawing, in which sludge load was decreasing with time, had the advantage in both of the performances.
