briefs a flowchart of the biological process in the CWTP.
The main process is consist of aeration unitdanoxic unitdaeration
unit in sequence of wastewater flow, namely O/A/O process. The
process is operating in parallel. Each includes 4000 m3 and 8600 m3
aeration tanks (called O1 and O2 respectively), a 5000 m3 anoxic
tank, a primary sedimentation tank (380 m3
) and a secondary
sedimentation tank (500 m3
). It should be noticed that the O/A/O
process is actual an O1-A/O2 process, since only the water effluent
of O1 enters the anoxic tank whereas the sludge in the primary
sedimentation tank is returned to O1 at a ratio of 1. The underflow
from the secondary sedimentation tank flows back to the anoxic
tank at a ratio of 1.5 in order to supply the nutrient requirements of
the bacteria and maintain sufficient solids concentration. During
the process operation, the concentration of dissolved oxygen (DO)
is 2.3 mg/L in O1 and 5.2 mg/L in O2, respectively.