Geoscience Reference
In-Depth Information
EXAMPLE 24.86
Problem: The biosolids withdrawn from the primary settling tank contain 1.4% solids. The unit
influent contains 285 mg/L TSS, and the effluent contains 140 mg/L TSS. If the influent flow rate
is 5.55 MGD, what is the estimated biosolids withdrawal rate in gallons per minute (assuming the
pump operates continuously)?
Solution:
(285 mg/L
140 mg/L)
×
5.55
×
8.3
4
Biosolidsrate
=
=
40 gpm
0.014
××
8.34
1440 min/day
24.11.6.2 Biosolids Production in Pounds per Million Gallons
A common method of expressing biosolids production is in pounds of biosolids per million gallons
of wastewater treated.
Totalbiosolidsproductio
nn(lb)
Totalwastewaterflow(MG)
Biosolids(lb/MG)
=
(2 4.118)
EXAMPLE 24.87
Problem: Records show that a plant has produced 85,000 gal of biosolids during the past 30 days.
The average daily flow for this period was 1.2 MGD. What was the plant's biosolids production in
pounds per million gallons?
Solution:
Totalbiosolids production(lb)
To
85,000 gal
× b/gal
1.2 MGD30days
8.34 l
Biosolids
=
=
=
19,692 lb/MG
talwastewaterflow(MG)
×
24.11.6.3 Biosolids Production in Wet Tons per Year
Biosolids production can also be expressed in terms of the amount of biosolids (water and solids)
produced per year. This is normally expressed in wet tons per year:
Biosolidsprod. (lb/
MG) verage dailyflow(MGD)
×
×
365 days/yr
Biosolids
(wet tons/yr)
=
(2 4.119)
20
00 lb/ton
EXAMPLE 24.88
Problem: The plant is currently producing biosolids at the rate of 16,500 lb/MG. The current aver-
age daily wastewater flow rate is 1.5 MGD. What will be the total amount of biosolids produced per
year in wet tons per year?
Solution:
Biosolidsprod. (lb/
MG)Average daily flow (MGD)
×
×
365 days/yr
Biosolids
(wet tons/yr)
=
20
00 lb/ton
16,500 lb/MG
×
1.5 MGD
×
365 days/yr
=
2000 lb/ton
4517 wettons/yr
=
 
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