The columns were operated in this closed circuit
fashion to allow the same inoculum to enter each of the sand
columns. Wastewater treatment plant effluent was selected
as the inoculum to reflect its role as a constant source of
microorganisms to SAT spreading basins. Other biota (native
soil microorganisms prior to wastewater application, plants,
etc.) that might affect SAT processes at full scale were not
included in this study. After the inoculation was complete
(9 h), influent lines were connected to sterile media flasks and
effluent lines were placed in a waste collection flask. Columns,
media flasks, and translucent tubing were covered in
aluminum foil to prevent algal growth and to inhibit PPCP
photolysis. The columns operated continuously in this
manner for 300 days.