TM 5-814-3/AFM 88-11, Volume III
(3) Determine weight of CaCO2 formed in reacting with SO4 hardness:
CaCO3 formed in reacting with CO and Ca (HCO3)2:
Solubility of CaCO3(25 mg/LL):
CaCO3 dissolved ' 25 mg/L 8.34
' 208 lb/mil gal;
Total CaCO3 weight 43 + 1,810 - 208 = 1,645 lb/mil gal.
Sum total solids weight:
Total solids weight = 1,750 (SS) + 23 (Fe(OH)3) + 1,645 (CaCO3) = 3,418 lb/mu gal.
At a flow rate of 4 mgd, the total solids weight becomes (3,418 lb/mu gal) (4 mgd) = 13,672 lb/day.
Calculate sludge volume, assuming an overall specific gravity of 1.06 and a moisture content of 93 per-
cent (7 percent solids):
3,418 lb/mil gal
' 738 cu ft/mil gal ' 2,952 cu ft/day.
Sludge volume '
1.06 (62.4 lb/cu ft)(0.07)
C-5. Single stage stone-media trickling filters. (Refer to para 12-2.)
a. Design requirements and criteria. Design a trickling filter to treat 2 mgd of primary settled effluent
under the following conditions:
Raw wastewater BOD5 = 250 mg/b;
Primary clarifier BOD5 removal efficiency 30 percent;
Required effluent BOD5 = 30 mg/b;
Design temperature = 20EC;
Design without and with recirculation.
b. Calculations and results.
(1) Design without recirculation.
Primary treated effluent BOD = 250 (1 - 0.3) = 175 mg/L;
175 & 30
Required trickling filter efficiency '
Since the design temperature is 20oC, no temperature correction is required as per paragraph 12-2e.
8.34 lb/mil gal
BOD loading to filter ' (2.0mgd) (175mg/L)
/L ' 2,930 lb/day.