Table 1.
Physiochemical properties of drainfield sand and soil (mean±standard deviation).
Data for soil texture, pH, and EC from De and Toor [14].
Fig 1.
A north-south longitudinal cross-section (not to scale) of the drainfields showing vadose zone and groundwater monitoring instruments: (A) drip dispersal and (B) gravel trench systems.
Table 2.
Concentrations of chloride (Cl) and phosphorus forms in the septic tank effluent, background groundwater, and unsaturated and saturated zones of drip dispersal and gravel trench drainfields.
Fig 2.
Temporal variability in concentrations of (A) total P, (B) PO4–P, and (C) other–P in the effluent, unsaturated zone lysimeters located at 30.5 cm (L1), 61 cm (average of L2 and L3), and 106.7 cm (L4) below the infiltrative surface, and saturated zone piezometers (average of P1 to P5) located at >300 cm depth in the groundwater in the drip dispersal septic system.
Fig 3.
Temporal variability in concentrations of (A) total P, (B) PO4–P, and (C) other–P in the effluent, unsaturated zone lysimeters located at 30.5 cm (L1), 61 cm (average of L2 and L3), and 106.7 cm (L4) below the infiltrative surface, and saturated zone piezometers (average of P1 to P5) located at >300 cm depth in the groundwater in the gravel trench system.
Fig 4.
Mean (n = 64) percentages of PO4–P and other–P in the effluent, unsaturated zone lysimeters located at 30.5 cm (L1), 61 cm (average of L2 and L3), and 106.7 cm (L4) below the infiltrative surface, and saturated zone piezometers (average of P1 to P5) located at >300 cm depth in the groundwater in the (A) drip dispersal and (B) gravel trench drainfields.
Table 3.
Fixed effects test for total P, orthophosphate–P (PO4–P), and other–P.
Fig 5.
Least square means plot showing overall seasonal difference between dry (October–May) and wet (June–September) seasons for other–P in the drip dispersal and gravel trench septic systems (n = 64).