Question

Question 610 pts

A BOD test is run using 10 mL of treated wastewater. Chemicals to inhibit nitrification were added. The initial dissolved oxygen (DO) in the bottle is 9.5 mg/L and after 5 days, the DO is 5.0 mg/L. For the bottles that were allowed to run for 20 days, the DO is 4.0 mg/L. A similar test was done where nitrification was not inhibited. The initial DO was the same and the DO after 20 days was 3.0 mg/L. What is the BOD₅, ultimate BOD (BOD_u)  and the nitrogenous NBOD. BOD bottle volume is 300 mL.

B O D ( m g L ) = D 1 − D 2 ( m g L ) P

D1 = DO in bottle immediately after preparation

D2 = DO in sample after t days

P = fraction of sample volume to total volume

Group of answer choices

135, 165 and 195 mg/L

13.5, 16.5 and 19.5 mg/L

10.8, 43.8 and 33 mg/L

1350, 438 and 1080 mg/L

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Question 710 pts

You carried out solids analysis of a sample collected from an industrial site. The data is as follows:

Weight of crucible = 42.4523 g

Volume of sample = 25 mL

The weight of the crucible and dry solids after drying at 105°C = 42.4986 g

Weight of crucible and residue after burning off at 550°C = 42.4863 g

The total solids, volatile solids and fixed solids are

Group of answer choices

926, 246 and 680 mg/L, respectively

926, 680 and 246 mg/L, respectively

105.2, 56.0 and 49.2 mg/L, respectively

1052, 560 and 492 mg/L, respectively

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Question 85 pts

A wastewater sample was collected from a treatment plant and sent for quality analysis. The BOD test was carried out over 20 days. No chemicals to inhibit nitrification were added. The BOD value in this case is a measure of the concentration of ___________ in the wastewater

Group of answer choices

almost all carbonaceous and nitrogenous compounds

all organic and inorganic compounds present in the wastewater

particulate organic carbonaceous and nitrogenous compounds

almost all dissolved nitrogenous organic compounds

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Question 95 pts

During the_____________ phase, the number of microorganisms (in the BOD bottle) is more than during the _______________phase, but the rate of production is lower

Group of answer choices

declining growth, log growth

log growth, declining growth

declining growth, endogenous respiration

log growth, endogenous respiration

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Question 105 pts

Aerobic autotrophic bacteria

Group of answer choices

Get their energy from oxidation of inorganic compounds, e.g. NH₄, carbon from CO₂ and O₂ from air (or mixers)

Get their energy from oxidation of inorganic compounds, e.g. NH_4, carbon from CO₂ and do not need O₂

Get their energy from the sun (i.e. photosynthesis reactions) and carbon from CO₂

Get their en

Answer 1