FSM Paddle mixer is developed to roduce a constant edge speed that remains unaltered with incoming quantity changes. It combines high performance with low operating costs. The paddle mixer is used by placing it at the round grit's center and is driven by a geared motor located in a dry area. The arrangement of shape, size and number of paddles produce optimum flow in the tank to support waste water circulation and enhance the separating capacity. The deposited material then travels to the collecting hopper to be removed by suction pump or air jet lift. An optional aerated grease trap with an automatic skimming device can be installed.