History and Objectives: Due to problems and limitation associated with active sludge system with continuous and discontinuous current for the disposal of sewage, the present article present an active sludge system, without reversal of sludge with continuous current and continuous cycles and its efficacy in a laboratory scale is assessed.

Materials and Methods: The system consists of 2 reservoirs with dimensions, airation equipments, opening for entrance of sewage and exit of filtered water which have the same flow rate and with interchanging airation reservoirs and sedimentation function. MLSS, BOD5, TKN, NH3, SV1, MLVss, COD and DO test for efficiency were performed with the constructed sewage system and with city sewage system.

Results: Concentration of MLSS sewage, MLVss, F/M ratio during the operation and in each step was reduced. Efficiency of reduction of COD increase was from 87% to 98% and in the city sewage system from 85% to 91%. Assessment of the efficiency of the variable was positive.

Conclusion: The system had a high degree of efficiency. Further study on the final assessment and practical application of the system is recommended.