Bio-Septic tank is an anaerobic digester for treating septic water released from toilets. Tank has five compartments with interconnecting flow. Common Manholes with covers are provided on top of the compartments. Inoculum to digest the human waste is supplied with the tank. This is to be added before using the bio-septic tank. Poly-grass lining is provided in the First Two Compartments to provide large surface area and for supporting attached growth of anaerobic bacteria. Bio-Media (400 sq.m/cu.m) is filled in the Third and Fourth Compartment to increase the surface area for Bio-films and serve as growth medium for the bacteria. Last compartment can be used for storing/pumping/disinfecting the treated effluent.