TM 5-814-3/AFM 88-11, Volume III
(2) Determine total dosage rate for mineral addition, using an Al:P weight ratio of 2:1 and an Fe:P ratio
of 3:1.
2
Al
594 Alum
Alum dose = (50 lb/day Phosphorus
1 Phosphorus
54
Al
= 1,100 lb/day Alum;
= 265 mg/L as AL2 (SO4 )3.14H20.
162.35 FeCl3
3
Fe
FeCl3 dose ' (50 lb/day Phosphorus
1 Phosphorus
56
Fe
= 435 lb/day FeCl3;
= 104 mg/L FeCl3 = 36 mg/L as Fe.
c. Other methods available. The above examples are not to limit the designer*s selection of phosphorus
removal methods. They all should be investigated to determine the most cost effective. The designer should
refer to paragraph 15-7 for guidance.
C-13. Nitrification-denitrification. (Refer to para 15-9.)
a. Design requirements and criteria. Design a nitrification-denitrification system to treat 20 mg/L of
influent nitrogen. Use a separate stage configuration with suspended growth denitrification. Assume the
following conditions apply:
Wastewater flow rate = 1.2 mgd;
Temperature: 15EC;
Operating pH = 7.8.
Nitrification:
InfluentNH3-N concentration = 20 mg/L;
MLVSS = 2,000 mg/L;
Recycle = 100% of average flow.
There is no waste sludge.
Denitrification:
MLVSS = 2,000 mg/L;
Recycle = 75%;
Detention time = 2.5 hr.
b. Calculations and results.
(1) Determine loading:
NH3-N loading = 20 mg/L 8.34 lb/mil gal 1.2 mgd ' 200 lb/day NH3&N.
mg/L
(2) Determine tank volume. Use figure 15-4 to estimate the volumetric NH3-N loading at 15EC with
an MLVSS concentration of 2,000 mg/L:
&N
NH3
' 116.5;
lb/day
1,000 cu ft
1,000 cu ft
Tank volume = 200 lb/day NH3&N
' 12,120 cu ft.
&N
16.5 lb/day NH3
From figure C--8, get the performance efficiency and adjust taqnk volume accordingly: at pH = 7.8, the
efficiency is 88 percent.
Tank volume = 12,120 cu ft ' 13,773 cu ft.
0.88
C-35
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