Publication Summary

In 1991, the United States Environmental Protection Agency performed an analysis on the quality of domestic septage that formed the basis for managing septage under 40 CFR Part 503. That study was comprised of nine samples of domestic septage from Madison, Wisconsin. The results were used to determine loading rate calculations, based on the assumption that those nine samples had approximately the same probability distribution for pollutant concentrations as other domestic septage in the rest of the country.

In 1991, the United States Environmental Protection Agency performed an analysis on the quality of domestic septage that formed the basis for managing septage under 40 CFR Part 503. That study was comprised of nine samples of domestic septage from Madison, Wisconsin. The results were used to determine loading rate calculations, based on the assumption that those nine samples had approximately the same probability distribution for pollutant concentrations as other domestic septage in the rest of the country.

The analysis discussed here examines domestic septage quality using real-world monitoring data from three different facilities in Washington State that deal primarily with domestic septage. A 95% confidence interval to estimate the mean concentration (?) of pollutants and several nutrients in septage is determined and compared with the mean concentration of the corresponding EPA study characters. Compared to Washington State septage, this study finds that the EPA mean concentration value was below the 95% confidence interval for nine analytes (cadmium, chromium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc), was within the confidence interval for two analytes (phosphorus and total Kjeldahl Nitrogen) and was above the confidence interval for two analytes (arsenic and ammonia). All mean concentration ranges for Washington septage are below the Table 3 pollutant concentration limits of 40 CFR Part 503.