Waste Water Engineering Multiple Choice Questions on “Chemical Reactions Associated with Water Treatment”.
1. The chemical composition of wastewater naturally reflects the origin from which it came.
a) True
b) False
Answer: a
Clarification: Wastewater is the liquid end-product, or by-product, of municipal, agricultural, and industrial activity. As such, the chemical composition of wastewater naturally reflects the origin from which it came.
2. The world’s available fresh water supply is about _______ percent of that total water supply.
a) 10
b) 4
c) 3
d) 7
Answer: c
Clarification: The world’s available fresh water supply is about 3 percent of that total water supply. Only 20 percent of this amount is available for use in drinking water supplies. The remainder of the world water is salt water, which is costly to desalinate for drinking water purposes.
3. Which of the following related to the aerobic organic matter is true?
a) Essential nutrients for growth
b) Development of sludge deposits
c) Growth of undesirable aquatic life
d) Development of septic conditions
Answer: d
Clarification: Both nitrogen and phosphorus are essential nutrients for growth. These nutrients can lead to the growth of undesirable aquatic life. Their biological stabilization can lead to the depletion of natural oxygen resources and to the development of septic conditions.
4. ______ tend to resist conventional methods of wastewater treatment.
a) Suspended solids
b) Nutrients
c) Refractory organics
d) Priority pollutants
Answer: c
Clarification: Refractory organics tend to resist conventional methods of wastewater treatment. Typical examples include surfactants, phenols, and agricultural pesticides.
5. The quality of the fish habitat begins to increase when the dissolved oxygen concentration drops below 4 or 5 mg L-1.
a) True
b) False
Answer: b
Clarification: The quality of the fish habitat begins to decrease when the dissolved oxygen concentration drops below 4 or 5 mg L-1. Even if the receiving stream is at saturation, which is unlikely, that leaves only 3 or 4 mg L-1 of oxygen to be used for assimilation of the wastewater discharge.
6. Organic matter + nutrients + O2 → CO2 + H2O + _______
a) Biomass
b) O2
c) Nutrients
d) Organic matter
Answer: a
Clarification: This is the general form of the equation for decomposition of organic matter during the BOD test. It should be noted that oxygen is consumed in the reaction and biomass is the catalyst for the reaction.
7. 2NH3 +3O2 -> 2NO2– + ___ + 2H2O.
a) O2
b) 2H+
c) H+
d) 2O2
Answer: b
Clarification: This equation represents the first step of nitrification. Ammonia combines with oxygen to give nitrite and water in the presence of nitrosomonas bacteria. Two hydrogen free radicles are produced.
8. Which among these is the alternative BOD test for determining the oxygen consuming potential of a wastewater sample?
a) ThOD
b) COD
c) BOD
d) TOC
Answer: b
Clarification: An alternative to the BOD test for determining the oxygen consuming potential of a wastewater sample is the chemical oxygen demand (COD) test. As the name implies, the carbonaceous oxygen demand is oxidized chemically in the COD test.
9. What does SWOT stand for?
a) Solid Waste Operation and Treatment
b) Storm Water Operation and Treatment
c) Supercritical Water Oxidation
d) Storm and Wastewater Operation and Treatment
Answer: c
Clarification: Supercritical water oxidation (SCWO) is an intensive version of the WAO process. SCWO has become a rapidly developing innovative waste treatment technology for the oxidation of organic wastes and hazardous materials in water.
10. What is the combination of using a photocatalyst and UV or visible light for the treatment of wastewater and gaseous pollutants is called?
a) Photocatalysis
b) Super critical water oxidation
c) Advanced oxidation process
d) Wet air oxidation
Answer: a
Clarification: Photocatalysis is the combination of using a photocatalyst and UV or visible light for the treatment of wastewaters and gaseous pollutants. When illuminating a photocatalyst using UV or visible light, various organic compounds can be oxidized and mineralized at the photocatalyst surface or oxidized in solution ambient and atmospheric condition.
11. What is stoichiometry?
a) A quantitative relationship between reactants and products
b) Defines a qualitative value of the reactants and products
c) Defines the quantity of reactants and products upon reaching equilibrium
d) It defines quantity of only reactants