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

Citation:  Pp. 593-600 in On-Site Wastewater Treatment, Proc. Ninth Natl. Symp. on Individual and Small Community Sewage Systems (11-14 March 2001, Fort Worth, Texas, USA), ed. K. Mancl., St. Joseph, Mich. ASAE  701P0009.(doi:10.13031/2013.6066)
Authors:   D.M. Sievers, R.J. Miles
Keywords:   On-site sewage disposal, karst terrane, drip irrigation, performance evaluation, soil absorption

Three drip irrigation onsite systems were installed on forested private lots located in a karst sinkhole plain south of Columbia, MO. The systems replaced old aeration treatment devices (ATUs) that were discharging directly to sinkholes. The systems consisted of one drip irrigation system using septic tank effluent and two using water pretreated by ATUs. The systems were monitored for one year. Pump tank effluent was sampled monthly and analyzed for BOD, TSS, NH4-N, NO3-N, EC, pH, Na, and fecal coliforms. Soil samples were taken in each drip field at 15 cm intervals to 91 cm and analyzed for NH4-N, NO3-N, EC, and fecal coliforms. Ammonia was largely nitrified in the soil with the largest accumulation being 11 ppm. Nitrates accumulated in the soil over the winter but were greatly reduced during the summer months by up take of surrounding trees and grass or were leached. Fecal coliforms (MPN) were small and quite variable within a field and between fields. The numbers generally decreased over the summer due to drought conditions producing very dry soil. Aerobic slime bacteria developed in the drip lines of the septic drip system, reducing the field loading rate 60%. Flushing the lines with a 50% solution of commercial drain cleaners containing chlorine and sodium hydroxide restored the loading to 80% of the original.

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