Abstract: An apparatus and method for treating wastewater is provided including a cylindrical tank having a sidewall, a bottom, an upper portion and a lower portion; a hopper positioned within the tank, the hopper having sides, an upper opening located in the upper portion at a point above a desired water level within the tank and a lower opening located in the lower portion of the tank, the hopper sides diverging from the lower opening to the upper opening, the lower opening being smaller than the upper opening; a compressed air source; at least five radially spaced air outlet pipes, each air outlet pipe being fluidly connected to the compressed air source and extending downward into the lower portion of the tank and having an open end positioned above the bottom between the hopper and the sidewall of the tank so as to discharge air into an aeration zone between the hopper and the tank sidewall; an inlet line connected to the tank and having a discharge end opening into the tank between the hopper and the tank sides;