A akhbari - department of analytical chemistry faculty of chemistry razi university , kermanshah
A.A.L zinatizadeh - department of applied chemistry faculty of chemistry razi university kermanshah iran
y mansouri - department of analytical chemistry faculty of chemistry razi university , kermanshah
m irandoust - department of analytical chemistry faculty of chemistry razi university , kermanshah

A comparative study was carried out on performance of an integrated rotating biological contactor and activated sludge system RBC-AS and an up -flow aerobic/ anoxic sludge fixed film UAASFF bioreactor removing nutrient . The eexperiments were conducted based on a central composite design CCD and analyzed using response surface methodology RSM . the systems performance were assessed by varying four significant independent variables for RBC-AS hydraulic retention time HRT chemical oxygen demand to amonical nitrogen ratio COD/N , internal recirculation from the aerobic to the anoxic zone R and rotating disks speed R and three variables for UAASFF bioreactor hydraulic retention time HRT , chemical oxygen demand to ammonical nitrogen ratio COD/N-NH4+,and aeration time.