Abstract: A small and cost effective sewage treatment system intended for unattended use in individual homes, small industries or businesses in locations where a central sewage treatment plant is not available. The sewage treatment system comprises a conventional septic tank which drains into a smaller aerated holding tank, a pump to transfer effluent from the holding tank into a disinfecting chamber, a regenerative heat exchanger used to raise the temperature of the effluent while being aerated in the holding tank, means for pumping the effluent at a controlled rate through a microwave field, and a conventional drain field used to release the disinfected water into the surrounding soil. Operation of this system is fully regulated by a micro-controller, thereby eliminating the need for human intervention during normal use.