Environmental Engineering Exam 2 – Advanced Review Guide, Practice
Questions & Exam Preparation
Define BOD (explain the meaning of the term as "food" - correct answer ✔✔directly measures
amount of oxygen in water
indirectly measures amount of nutrients in water
Thody - correct answer ✔✔the amount of oxygen required to oxidize a substance to carbon
dioxide and water
COD - correct answer ✔✔oxygen consumption as a result of carbon oxidization
CBOD - correct answer ✔✔a method defined parameter is widely used as an indication of the
pollutant removal from wastewater.
NBOD - correct answer ✔✔Nitrogenous Biochemical Oxygen Demand
BOD5 - correct answer ✔✔the standard value for most wastewater analysis, indicator of total
waste strength
steps in a BOD test and possible problems - correct answer ✔✔1. BOD bottle filled with sample
that has been properly diluted and inoculated with microorganisms, bottle is stoppered to
exude air bubbles
2. blank samples containing only inoculated dilution water and stoppered
3. all bottles incubated in dark at 20C for 5 days
4. bottles are removed and DO concentration is measured, BOD is calculated
problems: different equations need to be used for different dilutions, step 4 equations differ by
amount of seed, some lab values of BOD5 overestimates actual oxygen consumption
, describe the standards drinking water must meet - correct answer ✔✔primary: MCL levels,
microbial, organics, inorganics, radionuclides, DBPs
secondary: color, taste, odor, hardness
contrast water sources in terms of quality - correct answer ✔✔ground water is better quality
that surface water. no solids, pathogens or NOMs ground water from well- ppt 7 slide 22
Explain how colloids are removed from water in drinking water treatment. - correct answer
✔✔colloids will not settle because they are too small, make colloids collide so they become
larger and are able to settle, alum: Adds attractive solids (Al(OH)3 and makes colloids attractive.
NEEDS ALKALINITY! Al2(SO4)3 + alkalinity = Al(OH)2 (solid)
Describe how to soften water - correct answer ✔✔Water softening is the removal of calcium,
magnesium, and certain other metal cations in hard water. The resulting soft water is more
compatible with soap and extends the lifetime of plumbing. Water softening is usually achieved
using lime softening or ion-exchange resins
Calculate all hardness parameters - correct answer ✔✔TH- Mg2+ hardness + Ca2+ hardness
NCH- TH-CH
CH- TH-NCH
CaH-
MgH
Define role of both pH and carbonate in softening - correct answer ✔✔hard water is usually
high in pH and carbonate levels and needs to be softened
Discuss the selection of a disinfectant - correct answer ✔✔chlorination- must dechlorinate,
takes longer, not so common,
Questions & Exam Preparation
Define BOD (explain the meaning of the term as "food" - correct answer ✔✔directly measures
amount of oxygen in water
indirectly measures amount of nutrients in water
Thody - correct answer ✔✔the amount of oxygen required to oxidize a substance to carbon
dioxide and water
COD - correct answer ✔✔oxygen consumption as a result of carbon oxidization
CBOD - correct answer ✔✔a method defined parameter is widely used as an indication of the
pollutant removal from wastewater.
NBOD - correct answer ✔✔Nitrogenous Biochemical Oxygen Demand
BOD5 - correct answer ✔✔the standard value for most wastewater analysis, indicator of total
waste strength
steps in a BOD test and possible problems - correct answer ✔✔1. BOD bottle filled with sample
that has been properly diluted and inoculated with microorganisms, bottle is stoppered to
exude air bubbles
2. blank samples containing only inoculated dilution water and stoppered
3. all bottles incubated in dark at 20C for 5 days
4. bottles are removed and DO concentration is measured, BOD is calculated
problems: different equations need to be used for different dilutions, step 4 equations differ by
amount of seed, some lab values of BOD5 overestimates actual oxygen consumption
, describe the standards drinking water must meet - correct answer ✔✔primary: MCL levels,
microbial, organics, inorganics, radionuclides, DBPs
secondary: color, taste, odor, hardness
contrast water sources in terms of quality - correct answer ✔✔ground water is better quality
that surface water. no solids, pathogens or NOMs ground water from well- ppt 7 slide 22
Explain how colloids are removed from water in drinking water treatment. - correct answer
✔✔colloids will not settle because they are too small, make colloids collide so they become
larger and are able to settle, alum: Adds attractive solids (Al(OH)3 and makes colloids attractive.
NEEDS ALKALINITY! Al2(SO4)3 + alkalinity = Al(OH)2 (solid)
Describe how to soften water - correct answer ✔✔Water softening is the removal of calcium,
magnesium, and certain other metal cations in hard water. The resulting soft water is more
compatible with soap and extends the lifetime of plumbing. Water softening is usually achieved
using lime softening or ion-exchange resins
Calculate all hardness parameters - correct answer ✔✔TH- Mg2+ hardness + Ca2+ hardness
NCH- TH-CH
CH- TH-NCH
CaH-
MgH
Define role of both pH and carbonate in softening - correct answer ✔✔hard water is usually
high in pH and carbonate levels and needs to be softened
Discuss the selection of a disinfectant - correct answer ✔✔chlorination- must dechlorinate,
takes longer, not so common,
