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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

 

Need Some Help? answers@engineeringfundamentals.com - James C. Young Environmental - Balestie, Irwin & Balestie