Three laboratory scale units are designed for work with intermittent activated sludge system against one laboratory scale unit with continuous feed system. The Work was divided into four operational stages by changing hydraulic retention time for each stage (6, 12,18, 24 hrs), and changing F/M during stage (1.5- 1, 0.6, 0.3, 0.1) BOD mg/l /MLVSS mg/l. Results showed that efficiency of reactors that work by intermittent feed were higher than the continuous feed reactor, their high efficiency for (BOD, COD, PO4) were (100, 99.809, 99.29)% respectively for intermittent feed reactorsand (94.68, 96.5, 88.65)%respectively for the continuous feed reactor. And increase efficiency with decrease F/M and increase HRT. and best HRT, F/M and intermittent time were (0.1-0.3), 24 hrs and (2/2, 3/3 hr/hr)respectively.