-Dosing rate - For the first six months of the experiment the mound sand columns were
dosed at two gallons per square foot per day for high quality effluents, and one gallon per
day for the lower quality effluents. The actual daily dose volumes for the three inch (.25
ft) inside diameter columns were calculated by determining the surface area of the
column, as pi R2 [3.14 x 0.125 ft x 0.125 ft = 0.049 ft2], which means 0.049 gallons (186
mL) would be added daily to each column for a one gallon per square foot per day dose
and 0.098 gallons (372 mL) for a two gallon per square foot per day dose. The effluent
was administered in five equal doses (37 and 74 mL respectively) per day with four
doses spaced four hours apart and the last dose of the day administered after an eight hour
interval. An exception to this dosing schedule was that one 24" column was dosed once
per day only. During the final ten weeks of the experiment, the dosing volumes were
doubled for eight weeks, and then doubled again (four times the original volume) for the
final two weeks.
-Saturation - Saturation was never achieved. Some drying occurred between each dosing.
-pH- For this study pH of the effluent was unaltered.
-Temperature - All tests were run at 200 C.
-Time - The leachate from each column was tested for organism pass through every three
weeks during the first 30 weeks of the study and then with increasing frequency during
the last weeks, peaking at three times per week at the end of the experiment.
-Cation concentrations were unaltered.
-Dosing effluent quality - Two small scale on-site waste water facilities were chosen for
collection of septic tank effluent to be used for dosing the experimental sand columns.
Site one. This system consisted of a septic tank vault followed by a single pass sand
filter, preceding the infiltration field. Samples were collected from the pumping tank just
after the sand filter. This site was chosen to represent a high quality effluent with
biological oxygen demand (BOD) and suspended solids (SS) values of less than 30/30
mg/L.
Site two. Samples were collected from a small scale on-site treatment system serving a
mobile home park. The system consisted of three septic tank vaults in series followed by
a recirculating sand filter in line prior to the infiltration beds. The samples were collected
directly from the surface of the third septic vault. Site two was chosen to represent a
typical effluent from a conventional septic tank with BOD/SS levels of approximately
220/150 mg/L.
Effluents from both systems were collected once per week and stored at 2-4° C
prior to being dosed to the columns. Each weekly collection of effluents was tested for
BOD and SS. These results are summarized in tables 1 and 2 below.

2