Environmental Engineering Reference
In-Depth Information
Seed material BOD eed in
×
dilution (mL)
5
Seed correction
=
(16.6)
300 mL
DO
(mg/L)
DO
(mg/L)
Se
ed correction
× 300
L
start
final
BOD(seeded)
=
(16.7)
5
Sample volume(mL)
Example 16.7
Problem: Using the data provided below, determine the BOD 5 :
BOD 5 of seed material = 90 mg/L
Seed material = 3 mL
Sample = 100 mL
Start DO = 7.6 mg/L
Final DO = 2.7 mg/L
Solution :
90 mg/L 3mL
300 mL
×
Seed correction
=
=
0.90 mg/
L
[
] × 3000mL
(7.6 mg/L
2.7 mg/L)
0.90
BOD seeded)
=
=
12 mg/L
5
100 mL
Bod 7-d ay M oving a verage
Because the BOD characteristic of wastewater varies from day to day, even hour to
hour, operational control of the treatment system is most often accomplished based
on trends in data rather than individual data points. The BOD 7-day moving average
is a calculation of the BOD trend.
Note: The 7-day moving average is called a moving average because a new aver-
age is calculated each day by adding the new day's value to the six previous days'
values.
BOD
+
OD
+
BODB
+ OD
day1
day2
day3
day4
+
BOD
+
OD
+
BOD
day5
day6
day7
7-Dayaverage BOD
=
(16.8)
7
Example 16.8
Problem: Given the following primary effluent BOD test results, calculate the 7-day
average:
June 1
200 mg/L
June 2
210 mg/L
June 3
204 mg/L
 
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