|
Bunnell, J. F., R. A. Zampella, M. D. Morgan, and D. M. Gray. 1999. A comparison of nitrogen removal by subsurface pressure dosing and standard septic systems in sandy soils. Journal of Environmental Management. 56:209-219. (Summary)
The New Jersey Pinelands region is characterized by sandy soils and is underlain by an extensive water-table aquifer. Due to the threat of nitrogen contamination by septic systems, Pinelands Commission regulations require 1.3 ha lots for homes served by standard septic systems. For development on smaller lots, the Commission permits the use of subsurface pressure-dosing septic systems. Standard systems rely on gravity for wastewater distribution, whereas pressure-dosing systems discharge a specific volume of wastewater to the disposal field through low-pressure doses. The Commission based the policy that permits the use of pressure-dosing systems in the Pinelands on the assumption that these systems remove a substantial amount of wastewater nitrogen. We tested this assumption by completing a field study that compared nitrogen removal in subsurface-pressurized and standard gravity-flow septic systems on sandy soils. All systems served single-family homes. For each system, the septic tank, pump tank (pressure-dosing systems only), and top and bottom zones of the disposal field were sampled. Laboratory analyses were completed for nitrite, nitrate, ammonium, and Kjeldahl nitrogen. There was no significant difference in nitrogen removal between the two types of systems. We found average nitrogen-removal rates of 40% and 48% for eight pressure dosing and 11 standard systems, respectively. In both types of systems, most nitrogen removal occurred between the septic tank and the top zone of the disposal field. In the majority of both system types, no additional change in nitrogen occurred between the top and bottom zones.
|
|
