ment on the projected soil profile efflux NO3-
N concentration levels at the site. Additionally,
the wastewater dosages were changed to more
accurately reflect those intended for the site.
The simulations were continued until the long-
term trend of the NO3-N outflow was discern-
ible. The input data more accurately repre-
sented the proposed soil renovation treatment
based on either 4 or 10 mg NO3-N/L in
wastewater and approximately 104 cm
of wastewater applied per cycle. These
two N concentrations were used to rep-
resent the design- and worst-case N lev-
els in the effluent. (Earlier simulations
a. 4 mg NO3-N/L applied.
used 4 mg NO3-N/L at a depth of 21 cm.)
The application volume (ponding depth)
was determined from a loading rate of
4.6 million gallons/day for two consecu-
tive days, on an 8-acre surface (two cells,
each having an area of 4 acres). The ap-
plication was followed by a 10-day rest.
From the data provided by the Philadel-
phia District of the Corps of Engineers,
an initial concentration of 0.5 mg NO3-
N/L was assumed in the entire soil pro-
The simulations were conducted for
seven 12-day cycles with 104 cm of 4 mg
NO3-N/L applied each cycle, and also
five 12-day cycles with 104 cm of 10-mg
NO3-N/L wastewater applied each
b. 10 mg NO3-N/L applied.
Additionally the two simulations were
run sequentially, with applications of 4
mg NO3-N/L followed by a series of
applications of 10 mg NO3-N/L.
The initial ammoniacal N was assumed
to be 5.0 mg/L NHx-N, based on data
provided by the Philadelphia District of
the Corps of Engineers.
The following input data and assumptions
were the same as those used for the earlier
simulations. As stated before, these are conser-
vative assumptions and estimates, represent-
ing worse-than-expected conditions.
The soil depth to the water table was set
108 120 132 144 156
72 84 96
at 150 cm (4.9 ft), which is conservative.
Temporary water table mounding dur-
c. Days 189, 4 mg NO3-N/L in wastewater; days 90156, 10
ing infiltration could conceivably raise
mg NO3-N/L in wastewater.
the water table significantly for short
periods. This effect would most likely in-
Figure 4. NO3-N efflux from the soil profile during wastewater
crease denitrification by reducing the av-
application (12-day cycles).