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WWWT - tutorial 1
Water And Wastewater Treatment Design (University of Strathclyde)
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lOMoAR cPSD| 11987058
CL 402 Water Engineering 2
17 409 Water and Wastewater Treatment Design
Tutorial 1
Problems and study questions
1. The following information is available for a seeded 5-day BOD test conducted on a
wastewater sample. A volume of 15mL of the waste sample was added directly into a
300mL BOD incubation bottle. The initial DO of the diluted sample was 8.8 mg/L and
the final DO after 5 days was 1.9 mg/L. The corresponding initial and final DO of the
seeded dilution water was 9.1 and 7.9, respectively. What is the 5-day BOD (BOD5) of
the wastewater sample? Ans. 115 mg/L
2. The wastewater is diluted by a factor of 1/20 using seeded control water. DO levels in
the sample and control bottles are measured at 1 day intervals. The results are shown in
Table 1, below. An aliquot of 1 mL of seed material is added directly to diluted and
control bottles. Calculate daily BOD values for the week.
Table 1. Change in dissolved oxygen with time
DO (diluted
Time (days)
sample)
0
7.98
1
5.05
2
4.13
3
3.42
4
2.95
5
2.6
6
2.32
7
2.11
DO (seeded
control)
8.25
8.18
8.12
8.07
8.03
7.99
7.96
7.93
Answers
BOD (mg/L)
57.2
74.4
87.6
96.2
102
107
111
3. What are some of the limitations of the BOD5 test?
4. What is nitrification?
5. Laboratory determinations on an industrial wastewater indicate that its BOD5 is
630mg/L and the k1 value at 20oC is 0.2d. Calculate the ultimate BOD of the waste.
Ans. 700mg/L
6. What would be inferred if the chemical oxygen demand (COD) for the wastewater in
question 5 is 6,000mg/L?
7. What are some of the challenges in treating organic & inorganic contaminants and
pathogenic organisms in wastewater?
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