Unit 3-5 Flashcards
1
Q
What is waste water treatment
A
The removal of undesirable components to improve quality to release into the environment via physical, chemical or biological processes
2
Q
Objectives of biological treatment
A
Reduce BOD and Convert majority of organic compounds into stable biomass, which can be settled as sludge.
3
Q
Two biological treatment systems
A
Lagoon and activated sludge
4
Q
Lagoons are categorized as ____________-growth systems
A
Suspended
5
Q
What are three broad levels/stages of wwt
A
- Primary/preliminary
- Secondary
- Tertiary
6
Q
Goals of primary treatment
A
To remove large materials and corse solids to enhance subsequent treatments
Remove course and settleable solids
Equalize WW flow
Neutralize flow
7
Q
What are comminutors and when are they used?
A
After course screens where fine screens aren’t used.
Grinds up remaining solids
Dried, baled and sent to landfill
Or sent to next stage
8
Q
What level would you find a grit chamber?
A
Preliminary
9
Q
Neutralization is a commonly used in municipal waste water treatment plants
A
Yes?
10
Q
Grit chamber sludge vs sludge at the bottom of 1• clarifier
A
Removal of Inorganic solids vs organic solids
11
Q
What is the purpose of 2• biological treatment?
A
Removal of suspended solids, mainly organics, no removed by preliminary treatment
Remove dissolved biodegradable organics
Nitrogen and phosphorus
12
Q
Aerobic vs anaerobic
A
Bacteria consume organic pollutants as food
Organics+O2 –> CO2+H2O+energy+biomass
Absence of O2
Organics -> CO2+CH4/acid+energy
Very slow and sensitive
13
Q
Where is anaerobic digestion used?
A
Sludge digesters
14
Q
Factors affecting bacteria digestion rate/processes
A
Food/nutrients (N P K S Ca Mg)
Temperature
Oxygen
PH
Presence of toxins
15
Q
Why is the addition of O2 required (WWT)
A
To promote aerobic processes.
2mg/L
Ratio of nitrogen and phosphorus
16
Q
What is activated sludge
A
Settled sludge that contains living or active microbes that are retuned to the reactor (increasing available biomass and speed)
17
Q
What is mixed liquor
A
Combination of microbes and waste water in the reactor
18
Q
RAS
A
Return Activated Sludge
19
Q
WAS
A
Waste activated sludge
20
Q
What is the importance of pulp and paper industry in Canada
A
One of Canada’s largest and most profitable industries.
Employs 41,000 Canadian
Major export
21
Q
Source material for pulping
A
90% softwood & hardwood
Fibers->Cellulose
Recycled materials (paper/cardboard)
22
Q
Soft vs hardwood fibers
A
Soft Spruce/fir Long fibers High quality strength Bags and boxes
Hard Aspen, birch Short fibers Lower strength Printing paper (smooth and evenness)
23
Q
Main components of wood?
A
- Cellulose and hemicellulose organic fibers (used for pulp)
- Lignin (hold fibers together)
- Extractants (removed and recovered- ie fatty acids and turpentine)
24
Q
What is pulp
A
Pulp is the raw material used for paper. It is made of cellulose/fibers of wood.
25
What is pulping
Process of extracting fibers cellulose from wood or other raw material to make pulp
26
What are the two types ofpulping?
Mechanical and chemical
27
Which pulping process yields the most?
Mechanical
28
Which pulping process makes higher quality paper?
Chemical
29
4 types of mechanical pulping
SGW
PGW
RMP
TMP
30
Chemi-mechanical pulping types (2)
CTMP
BCTMP
31
What is the name for chemical pulping
Kraft
32
SGW
Stone Groundwood
33
PGW
Pressure Groundwood
34
RMP
Refinery Mechanical Pulp
35
TMP
Thermal Mechanical Pulping
36
CTMP
Chemi-thermo-Mechanical pulping
37
BCTMP
Bleached chemi-thermal Mechanical pulping
38
General processes/steps of pulping in order
1. Debarking
2. Wood chipping
3. Defibration/delignification
3. 1 liquor recovery
4. Bleaching
5. To paper plant or market
39
2 types of debarkers
Drum- logs tumble and roll in a large drum
Ring- fed and stripped through teeth on rotating heads
40
defibration vs delignification
removal of ligni from wood by mechanical (force and pressure), heat or chemical processes to release wood fibers
41
what is stone ground pulp
logs are pushed against a grindstone. teases fibers out. Lignin is retained.
High yield, bad quality
42
SGW vs PGW
Wood is ground in grindstone vs pressurized grinder
43
what is a refiner (pulp)
woodchips go into a large refiner
- large round metal disks
- spin opposite directions
- teeth
medium yield and quality
44
What is the raw material for thermo-mechanical pulp? What is the quality of paper produced
chips or fines exposed to high-pressure steam
yield high, quality better than other mechanical
45
Explain BCTMP process
```
woodchips,
washed/steamed/drained,
chemicals to soften and remove lignin
refiners,
pulp washed, screened and then bleached
```
46
What method of pulping is mostly used in canada
Kraft
47
Explain Kraft pulp process
Woodchips
High temp and chemicals (acidic sulfite and kraft- alkaline) break down chemical bonds of lignin.
sulfite added to enhance bleaching
liquor cycle
48
Explain Liquor recovery process (long answer test)
White->black->green->white
1. White (NaOH) is added to wood chips
2. Lignin dissolves into liquor and turns it black
3. black liquor is evaporated
4. Black liquor is then burnt to remove bonded lignin-> generates heat and electricity
4. smelt (inorganics) is recovered from boiler and water is added. Green liquor (Na2CO3)
5. causticize with Ca(OH) to return back to the white liquor
49
difference between white and black liquor
Lignin
50
Which yield more pulp, kraft or refiner mechanical?
mechanical
51
Give an example of energy recovery in liquor recovery cycle
When lignin is burnt out of black liquor to produce smelt. The heat from burning off the bonded lignin is used to make heat, steam, turn turbine and create electricity
52
Name three oxidant agents used in the bleaching process
Elemental Cl2
Chlorine dioxide (ClO2)
Oxygen (O2)
Ozone (O3)
53
what is the conventional method of bleaching? What is the concern?
Elemental Cl2
produces large amount of dioxins
- Toxic, cancerous, bioaccumulates
54
What are the purposes of mechanical and chemical bleaching?
mechanical- Remove chromorphores (pigments) not lignins
Chemical- remove all lignins
55
Difference between integrated and market pulp
Integrated (paper factory is with pulp factory)
Market pulp, pulp is packaged and sold to paper producer as raw material
56
4 components of a paper machine
1. Wet end (forms slurry, vibrated and gravity into a mat)
2. Pressing (removes water)
3. Drying (steam heated cylinders)
4. Calender (presses to desired thickness and unifrom)
5. sheets cut into desired sizes and baled/stacked/shipped
57
Energy use of pulp and paper (vs others)
Energy-intensive 30% of Canada's industrial energy use
| 3rd largest industrial polluter
58
What has been done to alleviate energy use in the pulp sector
Switching to renewable biomass for fuel/energy
increases in energy efficiency
59
How can pulping sludge be reused?
Very good fertilizer (biomass, N, P, wood fiber and water)
Crop yield increase and increases soil quality (ie. water retention)
60
Name environmental issues regarding pulp and paper
```
Energy-intensive
water intensive
water pollution (n, p, solids, chemicals and temp)
bleaching (toxic by-products)
sludge and toxic waste
air emmissons
deforestation
smell
Ink (heavy metals)
Paper is thrown out
```
61
There is always a textbook solution available for treatment of any raw water, as water treatment techniques are well
developed. (T/F)
No. Only generalized designs using a combination of several processes
62
Pre-sedimentation is an effective way to remove H₂S from untreated water. (T/F)
False. Pre-chorination step
63
What is meant by “water stabilization”?
pH adjustments
| Many processes are pH dependant (ie. coagulation)
64
Name three main treatment processes of water treatment.
Coagulation, Flocculation, Sedimentation, Filtration, Disinfection
65
Why suspended particles don’t settle down? What are the key processes to remove suspended particles?
Most have an electrostatic negative charge. Prevent from colliding and repel each other
Coagulation and Flocculation
Overcome charges and bring particles together to form larger particle (flocs) that settle faster
66
What is a coagulant? Which one is not a coagulant?
a. Alum or aluminum sulphate, AL₂(SO₄)₃
b. Sodium hydroxide (NaOH)
c. Ferric chloride, FeCL₃
A and C are cogulants
67
Turbulent flow is desirable during flocculation. (T/F).
False. Gentle mixing
68
Name three aesthetics factors of source waters.
Taste, color, ordor
69
Sedimentation basin (clarifier) is always right after a coagulator. (T/F)
False- flocculator
70
What are the fundamental differences between conventional and alternative sedimentation basins?
Space they need. Alternative make larger floccs that settle faster so the basin can be shorter
71
Why v-notch weirs are usually used in different basins of a water treatment plant?
Launders: outlet structure that takes water from the very top that all floccs have settled out of
72
```
Where is turbulence desirable?
A. clarifier
B. flocculator
C. coagulator
D. storage reservoir
```
C. Uniform distribution of coagulants
73
Name two types of conventional circular basin.
center feed and periferal feed
74
Why the bottom of many clarifiers is sloped?
settles sludge is swept by a scraper to the center into a collection chamber
75
When a DAF system is used?
When particles do not settle out easily (air diffuser, bubbles, fine floc attach to bubbles, skimmed of top, water collected lower in tank
76
What is the main purpose of filtration?
removing remaining suspended solids by passing through a porus medium
clays, silts, micobes, ions, flocs
77
Pre-sedimentation is an effective way to remove H₂S from untreated water. (T/F)
False. Pre-chlorination step
78
Concentration of pathogens and suspended particles in groundwater sources are often insignificant, yet many treatment plants include a filtration process for better treatment. Why?
Avoid the risk of something happening, like the walkerton tradgedy. It is a back up incase something goes wrong in the process or with the source
79
The pore size of a rapid sand filter should be smaller than the size of suspended particles. (T/F)
False. Larger. Stuck in pores or adhere to sand
80
When is a backwash cycle triggered?
1. a predetermined level of head loss
2. increase in filter effluent turbidity
3. at a pre-set interval
81
What are the functions of the under drain in a filter?
1. covers the floor of the filter box
2. support the filter media
3. collect and convey filtered water
4. distribute backwashed water and air
82
Direct filtration is the common system for rivers with variable turbidity. (T/F)
F. best waters with low and steady turbidity (lakes)
(coag-floc-filtration)
rivers are best in a conventional system (coag-floc-sedimentation-filtration)
Inline (ground and upland surface)
(coag, filtration)
83
Explain the purpose and steps of the jar test in detail.
To determine the optimal dosage of coagulants and optimal chemical conditions
1. Test color, turbidity, pH, and alkalinity of raw water
2. addition of coagulant (does differ) to 6 samples
3. mixing high to low
4. water settles for an hour
5. measure again and look for the sample with optimal does
84
Sedimentation basin (clarifier) is always right after a coagulator. (T/F)
False- flocculator
85
What are the fundamental differences between conventional and alternative sedimentation basins?
Space they need. Alternative make larger flocs that settle faster so the basin can be shorter
86
Why v-notch weirs are usually used in different basins of a water treatment plant?
Launders: outlet structure that takes water from the very top that all flocs have settled out of
87
two factors for effectiveness of disinfection
contact time and concentration
88
Name two types of conventional circular basin.
center feed and perifferal feed
89
Name two advantage and two disadvantages of chlorination.
Residual- protects water for a long time
cheap, quick, reliable and easy to use
- reacts with organics creating THM's and HAA's
- Potential health risk
- does not work on protoza
90
THMs and HAAs are by-products of ozonation. (T/F)
False. Chlorine
91
What is the main purpose of filtration?
removing remaining suspended solids by passing through a porus medium
clays, silts, microbes, ions, flocs
92
Ozonation is a very strong chemical disinfectant. (T/F)
True. Strongest. O3. Extra bond. toxic to most microorganisms
93
Concentration of pathogens and suspended particles in groundwater sources are often insignificant, yet many treatment plants include a filtration process for better treatment. Why?
Avoid the risk of something happening, like the walkerton tragedy. It is a back up incase something goes wrong in the process or with the source
94
Why do you think the use of UV technology for disinfection is on the rise?
reduced risk of toxic by-products,
People dont like the idea of ingesting Cl2
chemical free
95
Which disinfection technique is most common? Most effective? Most time-efficient?
Chlorine
Ozone (but no residual)
UV (no contact time)
96
When is water softening required in Prairie Provinces? Why?
when water sources are hard (high in Ca and Mg deposits) dolomite areas
97
Hardness should be removed from water as it has negative health impacts. (T/F)
False. Removed to increase lifespan of plumbing and machinery
build up, soaps and taste
98
Define water disinfection
The removal, deactivation or killing of pathogenic micro-organisms (bacteria, virus, protozoan)
found in all raw water
99
Groundwater sources often contain optimal level of fluoride. (T/F).
True. Added to surface water
100
What is the composition of sludges?
```
Mineral solids (clay/silt/sand)
chemicals from treatment process
```
101
Which source of water results in production of more sludge: surface or groundwater?
Surface- more TSS
102
Explain the general processes of sludge treatment.
Thickened (concentrated), Dewatered, Dried, baled, reused (fertilizer) or landfilled
103
What are the advantages of sludge thickening?
Reduces volume (reduces storage needs, transportation, disposal, processing)
104
How sludge can be reused?
fertilzer for cropland or golf courses
alum recovery
cement or bricks
105
Energy conservation and efficiency is very important in water and wastewater treatment plants, because this industry is energy-intensive. (T/F)
True
| Increasing demands and regulations
106
Why do you think the use of UV technology for disinfection is on the rise?
reduced risk of toxic by-products,
People don't like the idea of ingesting Cl2
chemical free
107
How sludge can be reused?
fertilizer for cropland or golf courses
alum recovery
cement or bricks
