In this paper, the Onsite Wastewater Differential Treatment System (OWDTS), a new approach for improving the traditional onsite wastewater treatment systems (OWTS), is proposed based on differential management and treatment of household wastewater effluents. Three fractions of household wastewater have been differentiated, reduced-volume blackwater, higher-load graywater and lower-load graywater. Based on this differentiation, different treatment processes required for each fraction are discussed. The procedure adopted for treatment of toilet wastes (reduced-volume blackwater) is shown. In the case of graywater, a sketch of treatment processes is provided. The OWDTS seems to be a new approach with higher potential for improvement of traditional OWTS, dry ecological sanitation, recycling of resources (toilet wastes and water), conservation of water resources, etc. Aerobic biodegradation of toilet wastes by using sawdust as a matrix is an essential treatment process of the OWDTS. Membrane technology seems to be the most effective process to treat higher-load gray water. Natural biodegradation of lower-load gray water by soil bacteria needs to be deeply studied.