Aerobic residential onsite sewage systems: an evaluation of treated-effluent quality.
This retrospective cohort study used existing data to evaluate the quality of effluent from three of the most common types of onsite residential aerobic treatment sewage systems (Multi-Flo, Norweco, and Whitewater) installed in Kitsap County, Washington. Five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), and fecal-coliform-bacteria parameters were used to determine performance. Although most (77 percent) of the systems were less than one year old at the time of sampling, over a third failed to meet NSF certification standards for BOD5 and TSS in effluent (< 30 milligrams per liter [mg/L]). Over two-thirds of systems failed to meet Washington State Board of Health Treatment Standard 2 criteria for BOD5 and TSS (< 10 mg/L). Furthermore, an average of 59 percent of the systems failed to meet state standards for fecal coliform (< 800 fecal coliform bacteria per 100 milliliters).
Maxfield
Meliss
M
Division of Drinking Water, Washington State Department of Health, 7171 Cleanwater Lane, Building 3, Olympia, WA 98504, USA. meliss.maxfield@doh.wa.gov
Daniell
William E
WE
Treser
Charles D
CD
VanDerslice
Jim
J
D015415:Biomarkers / Q000032:analysis; D015331:Cohort Studies; D015999:Multivariate Analysis; D012189:Retrospective Studies; D012621:Seasons; D012722:Sewage / Q000032:analysis*; D014861:Washington; D018508:Water Purification / Q000592:standards*; D014881:Water Supply / Q000032:analysis / Q000592:standards*
D015415:Biomarkers; D012722:Sewage