The number of permanent residents for a typical US residence is 2.5.

The typically recommended drainfield area per person is about 40 to 70 square meters. This varies from state to state in the United States. For a household with 2.5 people, a drainfield area of 100 square meters is generally recommended. Users can modify the area based on the number of people in a household. The parameters area and cap may be modified appropriately to study the effects of a larger population size using septic systems.

Biozone fecal coliform coefficient is normalized by the volume of biomass in the formula.

The biozone nitrification rate coefficient is normalized by the volume of biomass in the formula.

Biozone BOD coefficient is normalized by the volume of biomass in the formula.

The biozone denitrification rate coefficient is normalized by the volume of biomass in the formula.

The name of the septic system record is a primary key referenced by in . All names in the septic.str file must be unique.

An active system automatically becomes failing as the biozone layer gets clogged over time. A failing system turns to an active system after the user specified number of days for rehabilitation defined by t_fail.

The thickness includes the top soil layer and septic tank effluent (STE) distribution chamber including perforated pipe.

Data contained in the septic.str data file are: type of septic system, geometry of biozone, characteristics of biomass, and bio-physical reaction coefficients occurring in the biozone (adapted from Siegrist et al. (2005)).

References

Siegrist, R.L., J. McCray, L. Weintraub, C. Chen, J. Bagdol, P. Lemonds, S. Van Cuyk, K. Lowe, R. Goldstein, and J. Rada (2005): Quantifying Site-Scale Processes and Watershed-Scale Cumulative Effects of Decentralized Wastewater Systems. Project No. WU-HT-00-27. Prepared for the National Decentralized Water Resources Capacity Development Project, Washington University, St. Louis, MO, by the Colorado School of Mines.

An active system becomes failing as the biozone gets clogged and hydraulic failure occurs. A failing system automatically turns active during the simulation and septic parameters are re-initialized to default values after the specified number of days for rehabilitation. For testing long term failure, t_fail can be increased as per the failing duration. The parameter should be set to 2 for simulating failing conditions.

The biozone layer is thin soil layer underneath the septic tank effluent (STE) distribution chamber where pollutants are degraded by naturally existing live biomass bacteria.

The septic system type is a foreign key referencing name in septic.sep.