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Mechanical Aerators

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SAMPLE AERATION CASE STUDIES: biological nutrient removal (bnr)

Let's calculate an estimate of the solids retention time for a number of aerobic installations using the iterative formula - all data self-explanatory. Please be aware that these calculations are a simplification of the actual project data. For example, actual solids inventories could be smaller or larger and all other derived magnitudes adjusted accordingly. SRT is thus about ballpark.

SRT Sludge Age Sizer Dairy Biological Nutrient Removal
T 20 °C T 20 °C T 20 °C
Yoc 0.5 Yon 0.31 Ydn 2.28
Kd 0.200 Kd 0.200 Kd 0.200
flow in 2000 m3/d 0.528 mgd
CODin 483 mg/L 2126 lbCOD/day 964 kgCOD/day TKNin 44 mg/L
TKNin 44 mg/L (for nitrif!) 194 lbTKN/day 88 kgTKN/day
Nitrates 44 mg/L 194 lbCOD/day 88 kgNO3/day 0 used up for COD removal/growth
nVSS 0 mg/L 0 lbSS/day 0 kgSS/day TKNin used for growth 0 mg/L
Percent 100 % Treated 964 kgCOD/day TKNin avail for nitrification 44 mg/L
Percent 95 % COD removed 916 kgCOD/day
Vreactor 899300 gallon 3404 m3 (from order of magnitude sizing)
0.8993 mg 0.28 kgCOD/day per m3
Target MLVSS ballpark bug mix
1086 mg/L heterotrophs 3690 kg heterotrophs 1086 mg/L 68 % of Target MLVSS
61.5 mg/L nitrifiers 209 kg nitrifiers 62 mg/L 4 % of Target MLVSS
450 mg/L denitrifiers 1529 kg denitrifiers 450 mg/L 28 % of Target MLVSS
0 mg/L other solids 0 kg other 0 mg/L 0 % other (this entry's not used)
1598 mg/L
1598 mg/L 11967 lb bugs 5428 kg bugs
Heterotrophic Calcs
SRT     30.04 days (iterates automatically)
Yn = 0.134
biomass yield = 123 kg/day bugs
Global Sludge Age
Nitrifiers 30.01414 181 kg/day
SRT     30.16 days (iterates automatically) synthesis
Yn = 0.083
biomass yield = 7 kg/day bugs
Denitrifiers
SRT     29.93 days (iterates automatically)
Yn = 0.612
biomass yield = 51 kg/day bugs
HRT = V / Q = 1.7 days
41 hours

SAMPLE AERATION CASE STUDIES: petroleum refinery stream containing benzene:

Let's calculate an estimate of the required solids retention time for a small petroleum refinery stream containing benzene (1850 ppm -> COD = 1850* 3.08 = 5700 mg/L). Please be aware that these calculations are a simplification of the actual project data. For example, actual solids inventories could be smaller or larger and all other derived magnitudes adjusted accordingly. SRT is thus about ballpark.

SRT Sludge Age Sizer
T 25 °C
Yoc 0.5 Petroleum Refinery Stream
Kd 0.250 (also called b) Stream containing about 1850 ppm benzene
Carbonaceous Removal Sludge Age
flow in 240 m3/d 0.063 mgd
CODin 5700 mg/L 3011 lbCOD/day 1366 kgCOD/day applied
0 kgCOD/day via denitrif
1366
Percent 100 % Treated 1366 kgCOD/day
Percent 98 % COD removed
Vreactor 190440 gallon 721 m3 (from order of magnitude sizing)
0.19044 mg 1.89 kg applied COD/day per m3 (Residual OK)
Target MLVSS 1.89 kg applied + from denitri COD d/m3
5320 mg/L 8439.463 lb bugs 3828 kg bugs total bugs in tank but say only 100.0 % heterotrophs
5320 mg/L 8439.463 lb bugs 3828 kg bugs (heterotrophic biomass)
SRT     20.04 days (iterates automatically)
Ync 0.143 ok f/m 0.357 kg AppliedCOD d per total kg bugs (Residual OK)
f/m 0.357 kg Applied + From Dentir / total kg bugs
biomass yield = 191 kg/day bugs due to appliedCOD
HRT = V / Q = 3.0 days
72 hours ok

 

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