Water surface contacting cover system-the basic study for improving the oxygen transfer coefficient and the BOD removal capacity

As a result, only by adding a slant plate, the oxygen transfer coefficient (KLa) increased approximately by 15% more than that with a SRAS basin. And the slope of slant plate was optimized at 10°. Additionally, in the WSCCS, the increasing efficiency of the oxygen transfer coefficient, affected only by the cover, was proved at about 25% on the lab-scale aeration basin and about 20% on the pilot plant. After all, the increasing effect of the oxygen transfer coefficient on WSCCS that was installed with the water contacting cover and the slant plate on standard aeration basin was proved to be above 35%. The distance between the air diffuser and the slant plate was 20-30 cm in the pilot-scale plant. As an effective factor for increasing the oxygen transfer rate, the width/depth ratio of aeration basin was proved to be 2. Through the short-term results of actual sewage treatment plant, it was known that BOD removal efficiency could be improved by about 3% by adopting tile WSCCS not but SRAS.