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EFFLUENT QUALITY IN SATURATED MOUND AND MODIFIED MOUND TOES RECEIVING SEPTIC TANK OR AEROBICALLY TREATED DOMESTIC WASTEWATER

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  701P0104,  . (doi: 10.13031/2013.15791)
Authors:   Eric M. Blasing and James C. Converse
Keywords:   Seasonal saturation, Wisconsin mound, Wisconsin modified mound, mound toe, surface discharge, fecal coliform bacteria, anaerobic, aerobic, domestic wastewater

Fifteen mound and modified mound systems with occurrences of saturation at the mound toe were sampled from the summer of 2001 to the fall of 2002. The mound systems received either anaerobic or aerobically treated domestic wastewater. Samples, taken from mound toe samplers and tile drains, were evaluated on the basis of mound performance using fecal coliform bacteria as the primary indicator. Soils at the fifteen sites ranged from silt loam to clay and pretreatment devices included four septic tanks, seven aerobic treatment units (ATUs), and four packed bed filters. Effluent was distributed via pressure distribution to all systems and approximately 50% of the soil dispersal units received effluent to only half of the infiltrative surface. Samples were taken only when the mound toe experienced saturated conditions.

Results from this study showed that mounds and modified mounds generally treat domestic wastewater during seasonal saturation to below body contact standards for fecal coliform bacteria. The mounds and modified mounds receiving septic tank effluent, ATU effluent, and packed bed filter effluent effectively reduced fecal coliform bacteria to geometric mean values of 9, 160 and 6 col./100 mL, respectively. When all pretreatments were evaluated together as a single group, the geometric mean fecal coliform count was 79 col./100 mL. BOD5 geometric mean values of mound toe effluent were 4, 2, 5 and 2 mg/L for all pretreatment influent, septic tank influent, ATU influent, and packed bed filter influent, respectively, to the mound. Also, all categories had a total nitrogen reduction of at least 55% from the pretreatment effluent to mound toe effluent.

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