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

Citation:  Pp. 225-234 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:10.13031/2013.6031)
Authors:   D. L. Lindbo, V. L. MacConnell
Keywords:   Pre-treatment, Peat filter, Effluent, Septic system

Soil and landscape conditions of the North Carolina lower coastal plain combine to hinder the use of conventional on-site systems. This can be of particular concern when an existing system fails to work on a site that by todays standards is considered unsuitable. To avoid the condemnation of a residence, alternative systems are utilized to reduce space requirements and treat the wastewater prior to subsurface disposal. Research evaluated a peat biofilter system installed at several sites on the lower coastal plain. All sites had existing houses with failing septic systems that were replaced with a peat bio-filter treatment system followed by subsurface disposal of the treated effluent. Site 1 is located on a clayey soil with a seasonal high water table between 15 and 45 cm. Sites 2 and 3 are located on small lots with high water tables and deep sandy soils. Site 4 is located on a small lot with a high water table and fill over organic soil. Systems at sites 2, 3, and 4 have been performing with a 93 to 99% reduction in fecal coliform, biochemical oxygen demand (BOD5), and total suspended solids (TSS). Ammonium (NH4-N) was nearly totally converted to nitrate (NO3-N) in the filter. Nitrate was detected in the nitrification trenches as well as directly below the trenches. In general the nitrate levels down gradient of the system were similar to those observed in background wells. The system at site 1 functioned similarly for over two years but in the fall of its third year of operation the filter saturated, became anaerobic, and ceased to treat the septic tank effluent effectively. The cause of the failure was linked to excessive ground water infiltration into the septic and pump tanks and poor soil conditions. The excessive amounts of groundwater overloaded the filter thus causing its ultimate demise.

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