This research project characterized the composition of modern single residential source onsite raw wastewater and primary treated effluent (i.e., septic tank effluent, STE) to aid onsite wastewater system (OWS) design and management. A literature review was conducted to assess the current status of knowledge related to the composition of single source raw wastewater, identify key parameters affecting wastewater composition, and identify information gaps in the current knowledge. This information was supplemented by a field monitoring program to assess the composition of residential OWS raw wastewater and STE. Field investigations included quarterly monitoring (fall, winter, spring, and summer) at a total of 17 sites from three regions (Colorado, Florida, and Minnesota) within the U.S. to ensure that the results and information gained had broad applicability to the management and design of OWS. A tiered monitoring approach was utilized focusing on conventional constituents, microbial constituents, and organic chemicals. In addition, daily and weekly variability within the raw wastewater and STE were monitored. Information obtained was tabulated and graphically displayed to enable assessment and comparison of parameters that affect single source waste stream composition.

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