Environmental Engineering

Test 1 Material

100

What is the material balance equation for CSTR steady state conservative, outside of water?

0=Σ C_inQ_in-Σ C_outQ_out

200

What is risk (as a formula)?

CDI*Potency

300

What are the three types of ideal reactors?

CSTR, PFR and Batch

400

World population in 1850 has been estimated at about 1 billion. World population reached 4 billion in 1975. Find the growth rate?

1.1%/yr

500

At 25^O C and 1 atm SO₂ is measured to be 400 micro-grams/meter^{3 .}  If air quality standard is 0.17 ppmv, does this exceed the standard?

Hint: 64.06 is the molecular weight of SO₂

24.465=constant

No, it does not exceed the air quality standard of 0.17

Test 2 Material

100

What is Henry's Law? (As a formula)

Henry's constant * Pressure

200

What does BOD and DO stand for?

Biochemical Oxygen Demand and Dissolved Oxygen

300

If BOD₅ is 15mg/L and BOD_infinity is 21mg/L, what is the remaining BOD left after five days have elapsed?

21-15 = 6mg/L

400

What is the BOD₅ with the following numbers: 

DO_i= 10 mg/L

DO_f=2 mg/L

*using 12mL wastewater and 290mL for dilution 

BOD₅= 201mg/L

500

Integrate the following equation 

dDO= (K_r(DO_s-DO) -K_dL₀e^-tKd)dt

DO= DO_s- e^-Kt(DO_s-DO₀+KL₀t)

Test 3 Material

100

What is the pH of distilled water using the following equation 

H⁺= OH-

Hint

K_w=10^-14

OH^-= k_w/H

pH = 7

200

What are the steps for a systematic drinking water treatment 

1. Screen and grit chamber

2. Primary Sedimentation

3. Coagulation and Flocculation

4. Secondary Sedimentation

5. Filtration

6. Disinfectant contact

7. Distribution

300

A perfect emitter at all wavelength. What is this, as a theoretical abstraction?

Blackbody 

400

Jupiter is 7.8*10⁸ km from the Sun. Its albedo is 0.73. Calculate the effective temperature of Jupiter assuming that the Sun is the only energy source.

Hint S= 51.5 W/m²

σ= 5.67*10^-8 W/m²K^-4

S(1-α)/4σ= T_V⁴

T_v= 88.5K

500

Compute the current pH of freshwater in equilibrium with an atmospheric CO₂ concentration of 800 ppm.

Hints: CO₂(g) = CO₂ (aq);K_H = 0.033363 mol/L

Co₂(aq) +H₂O = H⁺ +HCO₃^- ;K₁ = 4.47*10^-7 mol/L

HCO₃^- = H⁺ +CO₃^2- ;K₂ = 4.68*10^-11

H₂O = H⁺ +OH^- ;K_w = 10^-14

pH = 5.46

Laboratory

100

Alkalinity and Hardness are expressed in what units?

mg/L-CaCO₃

200

What is the name of the solid fraction that is not dissolved and would be retained by a very small filter

Total Suspended Solids (TSS)

300

Is a lower or higher BOD/COD ratio value more suitable for water that needs to be chemically treated? Also, is chemical treatment or biological treatment more expensive? 

(Both answers must be correct.)

A low BOD/COD ratio value represents water that has to be treated chemically. 

Chemical treatment is more expensive.

400

Electrostatic repulsion keeps particles in water apart.

What type of treatment is used to cause particles to stick together for further treatment use?

In the Coagulation-Flocculation treatment procedure, the added coagulants neutralize the charge of water particles. (This will cause most particles to attract considering that most particles in water are negatively charged.)

500

In determining Alkalinity of your sample, the sample was titrated to two specific pH values. The corresponding volumes of acid added to obtain these pH values are needed to complete the experiment. 

Give the pH value that will supply variable "V_P" or "V_T"

V_P is found at pH ~ 8.3.

V_T is found at pH ~ 4.5

Miscellaneous

100

Favorite part of the course?

Nice.

200

What pH of water is typically safe to drink (as recommended by EPA)?

Anywhere from ( 6.5 - 8.5 )

300

Where did Professor Na get his B.E. in Environmental Engineering?

China!

(Tsinghua University)

400

Who had proctored our second midterm exam in class?

Prof.Na and his daughter

500

(Joke) An optimist, a pessimist and an engineer walk into a bar and there is a glass half-filled. What does the engineer say?

"The glass is twice as large as it needs to be."