### Question 39967

Verified

Environmental Engineering

\mathrm{NH}_{4}^{+}+2 \mathrm{O}_{2} \longrightarrow \mathrm{NO}_{3}^{-}+2 \mathrm{H}^{+}+\mathrm{H}_{2} \mathrm{O}

How many kg of oxygen is required for the complete conversion of 49 kg ofammonia (NH4-N) to nitrate (NO3 -N)? Remember that NH4-N is measured"as N", so you can assume 14 g NH4-N per mole of NH4*.

### Question 39965

Verified

Environmental Engineering

What is the pH required to decrease the manganeseconcentration in a water supply to 0.01 mg/L if themanganese is in the Mn2+ form?

\mathrm{Mn}(\mathrm{OH})_{2(s)} \leftrightharpoons \mathrm{Mn}^{2+}+2 \mathrm{OH}^{-}

K_{s p}=5 \times 10^{-15}

8.7

6.4

3.8

10.2

### Question 39964

Verified

Environmental Engineering

\text { What is the equivalent weight of } \mathrm{CaCO}_{3} \text { ? }

50 g/eq

O 20 g/eq

O 100 g/eq

O 12.2 g/eq

### Question 39963

Verified

Environmental Engineering

Estimate the total weight of sludge in a 200 m anaerobic digester at 45°C with a total solids concentration of 2.0%.Assume a density of 990 kg/m for water, and a specific gravity of 1.25 for the solids portion of the sludge.

194,040 kg

198,000 kg

O 198,827 kg

250,000 kg

### Question 39962

Verified

Environmental Engineering

Circle any statement(s) that are true. You may select more thanone.

Reaction rate coefficients derived from batch reactor experiments can be applied to any flow-through reactor

If the objective is to allow a chemical reaction to proceed, then plug flow reactors are more efficient than complete mix reactors

A tracer test can be used to determine the hydraulic residence time

If the objective is to allow a chemical reaction to proceed, then-complete mix reactors are more efficient than plug flow reactors

### Question 39961

Verified

Environmental Engineering

If 160 mg of NaOH are added to 1 m of water with no alkalinity and a starting pH of 7, what would be the approximate final pH?

O 5.4

D 8.6

O 2.4

O 11.6

### Question 39960

Verified

Environmental Engineering

Considering the redox reactions shown below, which are carried out by Nitrosomonas and Nitrobacter bacteria,respectively, how many moles of O2 are required to completely nitrify one mole of NH4* to NO3?

2 \mathrm{NH}_{4}^{+}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{NO}_{2}^{-}+4 \mathrm{H}^{+}+2 \mathrm{H}_{2} \mathrm{O}

2 \mathrm{NO}_{2}^{-}+\mathrm{O}_{2} \rightarrow 2 \mathrm{NO}_{3}^{-}

O 2 O 4 O 1.5 03 O 1

### Question 39959

Verified

Environmental Engineering

Place the unit operations and processes in the most likely sequence for a conventional biological activated sludge wastewater treatment plant with tertiary treatment.

### Question 39958

Verified

Environmental Engineering

Place the unit operations and processes in the most likely sequence for a conventional surface water treatment plant.

1st unit process in the sequence

2nd unit process in the sequence

3rd unit process in the sequence

4th unit process in the Sequence

5th unit process in the sequence

### Question 39957

Verified

Environmental Engineering

Circle any statement(s) that are true about the use of alum as a coagulant in a water treatment process. You may select more than one.

It will cause a decrease in the pH of a water with no alkalinity

It will consume the water's alkalinity, if available

It will cause an increase in the pH of a water with no alkalinity

If applied in combination with the correct amount of caustic soda, the pH of the water should not change much