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Wastewater > Introduction to Wastewater Treatment > Flashcards

Introduction to Wastewater Treatment Flashcards

1
Q

T/F Natural systems have enough assimilative capacity to treat wastewater from urban areas?

A

False. Natural treatment systems have a limited capacity to assimilate pollutants. Urban areas concentrate a large number of people and businesses into a small area and discharge them into one or a few locations. The result is reduced dissolved oxygen, fish kills, and other adverse effects.

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2
Q

T/F Wastewater treatment is necessary to protect public health and the environment?

A

True

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3
Q

T/F The term water resource recovery facility (WRRF) was recently adopted by Water Environment Federation because it better reflects our goals as a profession?

A

True

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4
Q

T/F Most of the fats, oils and grease present in influent wastewater comes from petroleum products?

A

False, most comes from animal sources like bacon.

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5
Q

A Pathogen is:
a: A bacteria or virus found in wastewater
b: Any organism capable of causing disease
c: Unable to survive for long periods outside wastewater
d: Dependent on TSS to reproduce

A

B

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6
Q

Solids that are retained by a 1.2 micrometer filter paper and are burned away in a 550 degree Celsius furnace are:
a: Total dissolved solids (TDS)
b: Total volatile solids (TVS)
c: Total volatile suspended solids (TVSS)
d: Total non-volatile dissolved solids (TVDS)

A

C

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7
Q

The biochemical oxygen demand (BOD) test measures this:
a: Biodegradable organic material
b: Percentage of organic suspended solids
c: Quantity of live bacteria
d: Amount of oxygen needed to stabilize wastewater

A

D

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8
Q

Solids that are able to pass through a 1.2 micrometer filter paper and remain unchanged after spending time in a furnace at 550 degrees Celsius may be described as:
a: dissolved and inorganic
b: suspended and inorganic
c: dissolved and organic
d: suspended and organic

A

A

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9
Q

Some treatment facilities are required to remove ammonia as part of their discharge permits for this reason:
a: There is a safe drinking water limit for ammonia
b: Ammonia reacts with organic matter in natural systems to form mustard gas
c: To protect downstream agricultural users from over fertilizing crops
d: Ammonia is toxic to fish and aquatic life

A

D

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10
Q

The biochemical oxygen demand (BOD) test is typically performed as a 5-day test for this reason.
a: It only takes the Thames River 5 days to reach the ocean
b: The bottles only hold enough dissolved oxygen for a 5-day test
c: The bacteria only live for 5 days
d: All of the organic material is consumed within 5 days

A

A

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11
Q

By definition, how much oxygen is required to stabilize or treat 1kg (lb) of BOD?
a: 1kg (lb)
b: 2kg (lb)
c: 3kg (lb)
d: 4kg (lb)

A

A

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12
Q

Which of the following pollutants is most likely to cause an algae bloom in a lake or river?
a: Total suspended solids
b: Biochemical oxygen demand (BOD)
c: Phosphorus
d: Turbidity

A

C

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13
Q

T/F: The Clean Water Act was promulgated in 1972

A

True

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14
Q

T/F: All direct dischargers are required to have a discharge permit?

A

True

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15
Q

T/F: The discharge permit system depends on accurate self reporting of effluent quality.

A

True

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16
Q

T/F: An operator will be fined and serve time in prison if the average effluent suspended solids concentration exceeds the limit given in the discharge permit?

A

False: The federal penalties only apply when a person knowingly and willfully falsifies, conceals, or covers up a permit violation or misrepresents a permit violation with fraudulent statements.

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17
Q

T/F: The monthly discharge monitoring report must be signed by the town attorney?

A

False: Permit applications and required reports must be signed by an authority sate-licensed individual of responsible charge, a principal executive officer, or ranking elected official.

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18
Q

T/F: U.S. EPA can set limits for heavy metals, cyanide, volatile organic compounds, and pesticides in direct discharge permits?

A

True

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19
Q

A WRRF has a 30 day monthly average BOD limit in their permit of 30 mg/L . Two samples were collected in May with results of 28 and 36 mg/L . The operator should:
a: Report only the first result to remain below the permit limit.
b: Average the results together and report a permit violation
c: Alter the second result to read 26 mg/L and then average the results together
d: Go back to his office and work on his resume.

A

B

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20
Q

The secondary treatment standards set effluent limits for these parameters:
a: BOD, CBOD, TSS, and pH.
b: FOG, BOD, and TSS
c: Nitrogen and phosphorus
d: Pathogenic organisms

A

A

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21
Q

ABC corporation manufactures tires in Metro City. All of the process water they generate is discharged to the sewer and is conveyed to the city’s WRRF. What type of discharger is ABC Corporation and who issues their discharge permit?
a: Direct; U.S. EPA
b: Indirect; state
c: Indirect; U.S. EPA
d: Indirect; city WRRF

A

D

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22
Q

T/F: Another name for a comminuter is a grinder?

A

True

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23
Q

T/F: A trash rack is a manual bar screen with openings between the bars smaller than 5 mm (0.25 in)?

A

False: Trash racks have wide openings to remove trash and large debris

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24
Q

Which of the following treatment processes would be considered a physical treatment process?
a: Grit Basin
b: Trickling Filter
c: Chlorine disinfection
d: Anaerobic disinfection

A

A

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25
Q

Sanitary sewers receive this type of flow:
a: stormwater
b: Municipal wastewater
c: Both stormwater and municipal wastewater
d: Both municipal and industrial wastewater

A

D

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26
Q

Most municipalities have stopped constructing combined sewers and are removing existing combined sewers for this reason:
a: Combined sewers deposit raw wastewater in rivers and lakes
b: combined sewers affect WRRF operation during and after storm events
c: Combined sewers are difficult to keep clean and can generate odors.
d: Combined sewers are expensive to construct due to larger pipe diameter.

A

B

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27
Q

Which technology are you likely to find in a a WRRF headworks?
a: Flow measurement
b: Primary clarifier
c: Ultraviolet disinfection
d: pond

A

A

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28
Q

The velocity of wastewater through a rectangular grin basin should be approximately ________ to allow grit to settle while keeping lighter particles in suspension.
a: 0.15 m/s (0.5 ft/s)
b: 0.3 m/s (1.0 ft/s)
c: 0.6 m/s (2.0 ft/s)
d: 1.5 m/s (5.0 ft/s)

A

B

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29
Q

A primary clarifier is capable of removing:
a: soluble BOD
b: Ammonia
c: Total suspended solids
d: Colloidal solids

A

C

30
Q

A WWRF using ponds for secondary treatment is equipped with a manual bar screen that has openings 5 cm (2 in) apart. What type of debris is most likely to be captured by this screen?
a: Branches
b: Rags
c: Small rocks
d: Paper

A

A

31
Q

T/F: Secondary treatment uses chemicals or bacteria to increase the size of particles in wastewater?

A

True

32
Q

T/F: WRRFs with secondary treatment typically remove more than 85% of influent BOD and TSS?

A

True

33
Q

T/F: Microorganisms in wastewater consume organic material in the wastewater to sustain themselves and reproduce?

A

True

34
Q

T/F: Secondary treatment systems do not typically include a clarifier or other solids separation processes after biological treatment?

A

False: The purpose of secondary treatment is to increase the size of particles remaining in the influent after screening degritting, and primary sedimentation. The biological solids grown during secondary treatment must be separated from the treated wastewater before before discharge using a secondary clarifier or other solids seperation process

35
Q

T/F: Ponds are typically unlined?

A

False: Lagoons are lined to prevent contamination of underlying groundwater. They may be lined with natural clay (bentonite) or with a synthetic liner.

36
Q

T/F: A well-functioning activated sludge process will be light tan to dark brown and have a small amount of white to tan foam on the surface?

A

True

37
Q

T/F: A rock media trickling filter should be completely submerged with no free space between the rocks.

A

False. Trickling filters are so named because the wastewater is trickled down over the media surface. Free space between pieces of media is required for air to penetrate and provide oxygen to the microorganisms that make up the biofilm.

38
Q

T/F: Biological treatment systems use the same microorganisms as natural systems, but are engineered to decrease treatment time by increasing the number of microorganisms in the treatment process?

A

True

39
Q

T/F: Disinfection uses chemicals or UV light to sterilize treated wastewater?

A

False: Disinfection reduces the numbers of bacteria and pathogens in the final effluent, but it does not sterilize the wastewater. Sterilization is the complete destruction or inactivation of all living things.

40
Q

Which of the following treatment processes would be considered biological treatment?
a: Alum addition for phosphorus removal
b: Activated sludge
c: Belt filter press
d: Ultraviolet disinfection

A

B

41
Q

A pond system is categorized as this type of treatment:
a: Primary
b: Suspended growth
c: Fixed growth
d: Physical

A

B

42
Q

Where do the microorganisms in ponds, trickling filters, and activated sludge systems come from?
a: They are added by the operator
b: They are naturally present in the in fluent wastewater
c: They spontaneously generate from suspended solids
d: The aliens beam them in every night

A

B

43
Q

This term is used to describe a collection of microorganisms growing on and attached to a media surface such as a rock:
a: Floc
b: Slime
c: Biofilm
d: Algae

A

C

44
Q

In a pond treatment system, what is the purpose of the last pond in the series?
a: Increases the risk of short-circuiting
b: Removes the biological solids produced in the first two ponds
c: Warms the wastewater before discharging
d: Acts as a primary clarifier or grit basin

A

B

45
Q

What is the primary difference between a pond treatment system and an activated sludge system?
a: Activated sludge recycles settled solids to the beginning of the process
b: Pond treatment systems use specialized, cold-tolerant bacteria
c: Activated sludge systems use algae for treatment
d: Pond treatment systems perform better at higher elevations

A

A

46
Q

For an activated sludge system, which of the following statements is FALSE?
a: Activated sludge requires less time to treat wastewater than ponds
b: Activated sludge is a suspended growth biological process
c: Activated sludge uses fungus to treat wastewater
d: Activated sludge holds the biological solids longer than the wastewater

A

C

47
Q

An example of a fixed-film treatment process is:
a: Activated sludge
b: Pond
c: Rotating biological contactor
d: Clarifier

A

C

48
Q

Which two methods of disinfection are most commonly used in domestic WRRFs?
a: Ozone and chlorine
b: Chlorine and UV light
c: Bleach and ozone
d: UV light and boiling

A

B

49
Q

Match the Unit Process to its place in the liquid treatment side

1: Collection system a: Pretreatment
2: Grit Basin b: Primary treatment
3: Primary clarifier c: Disinfection
4: Activated sludge d: Preliminary Treatment
5: Chlorine addition e: Secondary Treatment

A

1=A
2=D
3=B
4=E
5=C

50
Q

Match the liquid treatment type to its treatment goal:

1: Preliminary treatment a: Reduce number of bacteria and pathogens
2: Primary treatment b: Increase particle size for seperation step
3: Secondary treatment c: Protect downstream equipment
4: Tertiary treatment d: Remove nitrogen and phosphorous
5: Disinfection e: Decrease size and cost of secondary treatment

A

1=C
2=E
3=B
4=D
5=A

51
Q

T/F Sludge stabilization processes like digesters transform sludge into biosolids?

A

True

52
Q

T/F: Primary sludge typically contains between 2 and 6% total solids?

A

True

53
Q

T/F: The beneficial use of biosolids is regulated under 40 CFR part 258?

A

False: Biosolids are regulated under Section 503 of Title 40 of the CFR

54
Q

T/F: The time required for aerobic digestion depends on the temperature of the sludge?

A

True

55
Q

Put the following solids treatment processes into the correct order:
a: Dewatering
b: Secondary clarifier
c: Thickening
d: Digestion

A

Secondary clarifier, thickening, digestion, dewatering

56
Q

Screenings and grit are typically:
a: Sent to a landfill
b: Dewatered and land applied
c: Used for road base
d: Digested anaerobically

A

A

57
Q

Primary sludge consists of:
a: Microorganisms grown during treatment
b: Rags, plastic, and other heavy materials
c: Unprocessed, settleable organic and inorganic solids.
d: Grit and screenings

A

C

58
Q

Secondary sludge consists of:
a: Microorgnsisms grown during treatment
b: Rags, plastic, and other heavy materials
c: Unprocessed, settleable organic and inorganic solids
d: Grit and screenings

A

A

59
Q

This type of biosolids may be made avialable for public takeaway

A

A

60
Q

The vector attraction reduction requirement in the biosolids 503 regulations:
a: Limits concentrations of heavy metals in biosolids
b: Allows screenings and grit to be commingled with digested sludge
c: Reduces the likelihood that rats and insects will be attracted to finished biosolids
d: Prevents application of biosolids near streams and lakes

A

C

61
Q

Sludge thickening and biosolids dewatering are performed for this reason:
a: Reduces the total volume of sludge or biosolids
b: Required by the discharge permit
c: Reduces the total mass of sludge or biosolids
d: Required by the 503 regulations

A

A

62
Q

All of the following statements about anaerobic digestion are true EXCEPT:
a: reduces the amount of biosolids
b: Meets vector attraction reduction requirements
c: Typically paired with primary clarfiers
d: Break down solids in the presence of oxygen

A

D

63
Q

Anaerobic digester gas contains approximately:
a: 70% nitrogen and 22% oxygen
b: 65% methane and 35% carbon dioxide
c: 70% nitrogen and 30% carbon dioxide
d: 65% methane and 22% oxygen

A

B

64
Q

Match the process to its defining characteristic:

1: Aerobic digestion a: Uses lime to increase sludge pH
2: Anaerobic digestion b: Takes place prior to digestion
3: Thickening c: Breaks down sludge with oxygen
4: Dewatering d: Produces methane gas
5: Chemical stabilization e: Produces “cake” of up to 50% solids

A

1=C
2=D
3=B
4=E
5=A

65
Q

On a single rake screen, a limit switch:
a: Sets the upper and lower limits of travel for the rake
b: adjusts input line voltage
c: modifies the minimum particle size captured
d: turns off the drive motor if the rake is jammed

A

D

66
Q

One disadvantage of using comminutors and grinders is:
a: Reduced potential for clogged pipes and damaged equipment
b: Increased screenings disposal costs
c: Shredded material reduces treatment capacity downstream
d: More frequent overflows of the influent channel

A

C

67
Q

T/F: A WRRF with a combined sewer system is expecting a large storm. The manual bar screens are normally cleaned every hour. The operator should plan to decrease the cleaning frequency during and immediately after the storm.

A

False: Combined sewers bring both sewage and stormwater to the WRRF. After a storm, expect accumulated debris to be flushed from the collection system and into the WRRF. Cleaning frequency should increase.

68
Q

T/F: A shear pin is designed to break under a certain amount of force or pressure to prevent additional damage to equipment

A

True

69
Q

Screens should be cleaned before the head loss across the screen reaches _____________ or according to the screen manufacturer’s recommendations
a: 1 inch
b: 3 inches
c: 5 inches
d: 7 inches

A

B: 3 inches

70
Q

This type of control mechanism is best suited for storm events or other conditions that produce highly variable amounts of screenable material:
a: Clock timer
b: Level sensor
c: Particle counter
d: HOA switch

A

B

71
Q

A mechanical bar screen must be taken out of service for maintenance. Put the following steps in the correct order:
a: Shut down the screen according to the manufacturer’s directions
b: Close the upstream (inlet) gate
c: Close the downstream (outlet) gate
d: Wash the screen to remove debris
e: Drain the channel and remove debris
f: Lockout and tagout the equipment
g: Wash sides of channel and perform final draining of channel

A

A=3
B=1
C=2
D=6
E=5
F=4
G=7
(B,C,A,F,E,D,G)

72
Q

At minimum, how often should screens be inspected for visible and audible indications of possible malfunctions?
a: daily
b: weekly
c: monthly
d: quarterly

A

A

Wastewater (20 decks)

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