A biological treatment system, including a wastewater system drain field and at least one perforated distribution pipe located within the drain field and adapted to receive effluent. At least one perforated outer pipe surrounds the at least one distribution pipe to receive effluent from the at least one distribution pipe and to dispense the effluent to the drain field after it has been biologically treated in the at least one outer pipe. The system also includes a method of biological treatment comprising the steps of supplying effluent to at least one vessel positioned within a wastewater drain field; delivering gas to the at least one vessel to interact with the effluent such that the effluent experiences aerobic biological treatment; and passing biologically treated effluent from the at least one vessel to the wastewater drain field.