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EXECUTIVE SUMMARY <br />The State Water Resources Control Board (SWRCB) of California contracted with the <br />Department of Civil and Environmental Engineering to conduct a review of onsite wastewater <br />management systems. The results of the study are contained in this report. The information and <br />findings presented in this report were derived from (1) information supplied by manufacturers, (2) <br />the results of independent testing and reporting, and (3) information reported in conference <br />proceedings and journals. Performance information from the report is summarized in the tables <br />presented below. <br />The characteristics of typical septic tank effluent are provided in Table ES -1. A system for rating <br />system performance is presented in Table ES -2. Available information on treatment system <br />performance has been summarized in Table ES -3. When data were not available the <br />performance rating was left blank. <br />Table ES -1 <br />Characteristics of typical residential wastewaters <br />xvn <br />Septic tank Septic tank <br />effluent without effluent with <br />Constituent <br />Unit Untreated effluent filter effluent filter <br />BOD5 <br />mg/L 450 185 135 <br />TSS <br />mg/L 503 83 42 <br />TN as N <br />mg/L 70.4 70 70 <br />TP as P <br />mg/L 17.3 16 16 <br />FC <br />no./100 mL 106 106 106 <br />a Adapted from Crites and Tchobanoglous (1998). <br />Table ES -2 <br />Classification system for onsite wastewater treatment system performancea <br />Biochemical oxygen demand (BOD), <br />total suspended solids (TSS), and Total phosphorus Fecal coliform <br />Rating <br />total nitrogen (TN) (TP) (FC) <br />A <br />< 10 mg/L < 2 mg/L < 2 <br />B <br />< 20 mg/L < 5 mg/L < 800 <br />C <br />< 30 mg/L < 10 mg/L < 2000 <br />D <br />> 30 mg/L > 10 mg/L > 2000 <br />a Based on values <br />obtained from operational systems, independent certifications, and <br />experimental <br />systems. <br />xvn <br />