Wastewater treatment Flashcards
1
Q
Need to consider treatment to remove pathogens both entering ( ___ _____) and leaving ( ____ ____ ____) the watershed
A
- from wastewater
- for drinking water
2
Q
What is the law on returning water?
A
- must return to the source it came from
3
Q
What is portable water?
A
- safe to drink
4
Q
Is tap water sterile?
A
No
5
Q
How does the shower expose you to possible contaminants?
A
- diffuses and aerosolizes water
- can inhale and are exposed dermally
6
Q
What is used to remove organic matter from domestic/industrial effluent?
A
- microorganisms
7
Q
What is domestic waste made up of?
A
- gray water and wastewater from food processing
–> everything but sewage
8
Q
Where does sewage go?
A
- septic system
9
Q
Where does sewage go?
A
- septic system
10
Q
What does opportunistic mean?
A
- pathogenic potential but not a pathogen
11
Q
What does BOD stand for? What is it?
A
- biochemical oxygen demand
- measure of amount of dissolved oxygen consumed by microorganisms for oxidation of organic and inorganic matter
12
Q
Why does BOD need to be reduced?
A
- heavy organic material has high demand for degradation
- releasing it increases demand in receiving water depriving it of oxygen
13
Q
What does low available oxygen cause?
A
- low aquatic life
14
Q
What is used to lower BOD
A
microorganisms
15
Q
What is the difference in sizing of pipes from toilet vs sink?
A
- toilet large diameter
- sink small diameter
16
Q
How do some microorganisms reduce toxicity of poisonous substances (ex. cyanide/heavy metals)?
A
- oxidation, precipitation or volatilization
17
Q
contaminant levels should be low enough to be capable of ____ ______ after discharge into flowing, well-aerated surface water
A
- self purification
18
Q
What is self-purification?
A
- capacity to finish clean up
- natural process of purifying (ability of body of water to rid self of pollutants)
–> contaminant level must be low enough that when discharged the body of water can clean on its own
19
Q
What is the best form of self-purification?
A
- dilution - decreases levels of what is coming in and increases degradation
20
Q
What are the levels of wastewater treatment? What does this include?
A
- primary
- secondary
- tertiary
- physical and biological removal
21
Q
What is physical removal?
A
- filtration, physically pulling it out/depositing
22
Q
What is biological removal?
A
- degradation
23
Q
What is chemical removal?
A
- addition of compound that reacts
24
Q
What are the steps of primary treatment?
A
- physical separation where large floating material is screened out
- water flows through setting chambers (sand/grit removed, suspended solids sediment out)
- sewage solids collected
25
What is primary sludge?
- sewage solids
26
What removes oil and grease from water?
- skimmers
27
What is a biosolid? What happens to it?
- pulls out easy stuff (toilet paper/feces)
- left to sit and compost or transported
28
Explain setting chambers and give an example
- water sits to separate
- ex. salt in water not dissolved settles at bottom
29
Why is secondary treatment used?
to reduce organic load of sewage to an acceptable level
30
biological treatment procedures can be _____ or _____
- Anoxic
- anaerobic
31
What is used to measure the efficiency of secondary treatment process?
- biochemical oxygen demand
32
What is removed before secondary removal?
- as much as possible
- biofilm, bacteria and microbial masses
33
What is the goal moving to secondary treatment?
- having cleaner water
34
What is the goal of secondary treatment?
- reduce organic material (biological removal)
35
What is anoxic secondary treatment?
- series of digestive/fermentative reactions carried out by many different bacterial species
36
What is anoxic treatment carried out in?
- sludge digestors or bioreactors designed to support growth of anaerobic bacteria
37
What is an example of an anaerobic bacteria?
- methane-producing bacteria
38
What are the major products of anoxic treatment?
- methane and CO2
39
What needs to be considered in anoxic treatment?
- amount of space and equipment needed ESP W OXYGEN
40
What are digestive reactions?
- gases generated (carbon cycle under anoxic conditions)
- methane generated used as energy
- bacteria do the work
41
What is aerobic secondary treatment?
- trickling filter and activated sludge systems
42
What is a trickling filter?
wastewater sprayed onto bed of crushed rock; organic matter oxidized and adheres and microbial growth takes place (looks after itself)
43
What does trickling filter cause?
- mineralization of organic material to CO2, ammonia, nitrate, sulfate and phosphate
44
Why can't trickling filter be used in the city?
- need massive spaces and need to make sure nothing is added/aerosolization occurs
45
What is mineralization?
- broken down into minerals (basic)
46
Give an example of anoxic and aerobic treatment
- Anoxic - sludge digestor, activated by injection of oxygen
- anaerobic - trickling filter
47
What are activated sludge systems?
- wastewater is mixed and aerated in a large tank
48
What is a slime flock?
- suspended solid (bacteria, yeasts and molds) form mixture and are pumped into a clarifier
- want bacteria to adhere
- degrades, encourages breakdown
- flocks drop and settle
49
What is a clarifier?
- holding tank
50
What are flocs transferred to once they occur?
- anaerobic digestor
51
What do flocs go through first? What does this do?
activated aerated systems (activated sludge)
- rid easy stuff (more bacteria available to breakdown)
52
What is tertiary treatment?
- uses physical-chemical processes of precipitation, filtration and chlorination to reduce levels of inorganic nutrients
53
What inorganic nutrients does tertiary treatment reduce?
- phosphate and nitrate
54
Where does water go after tertiary treatment?
- river
55
What is ozone?
-O3
- highly reactive
56
What does water treatment focus on?
- "portable" water free of disease-producing microorganisms and chemical substances harmful to public health
57
What does water treatment attempt to decrease?
- turbidity
- taste and odour
58
What is used to decrease turbidity taste and odour
- Nuisance chemicals (Fe)
59
What does salmonella in water cause?
- typhoid
60
What does removing particles do? why?
- removes bacteria because they are attached
61
What are the 3 main stages in drinking water treatment process?
- sedimentation
- filtration
- disinfection
62
What is coagulation?
- liquid changing states to solid/semisolid
63
What is sedimentation?
- large reservoirs during holding period to remove sand, gravel and other large particles
64
What is flocculation?
- addition of aluminum sulfate
- grabs suspended parts and clumps together to remove bacteria and organic material
65
What does addition of alum aid in?
- formation of flocculent insoluble precipitate and absorbs organic matter and sediment material
66
approximately 80% of ____, ____ and _____ is removed during sedimentation stage.
- bacteria
- colour
- turbidity
67
What happens during filtration?
- large sand filters, dual or tri-media filters for municipal treatment (periodic backwashing)
- suspended particles and microorganisms removed
68
Why is filtration important in the removal of cysts or oocysts?
- resting and designed to hang to mammalian gut to complete life cycle
- TOLERANT TO CHLORINE IN DISINFECTION (MUST BE FILTERED)
69
What % of microorganisms are removed after filtration?
- 89-99.5%
70
What is filtration important in?
- removal of cysts/oocysts as they are tolerant to chlorine
71
What forms oocysts? What forms cysts?
- cryptosporidium (hidden spore)
- Giardia
72
What do tri-media filters use?
- carbon
- anthracite
- sand
73
What is disinfection used for?
- used primarily to ensure protection against post-treatment contamination (chlorine reacts with everything but consumed by organic material)
74
Why would disinfection be used prior to filtration?
- reduces biological growth in filter columns
75
What are the common chemical oxidizing agents in filtration?
- sodium or calcium hypochlorite
76
What is the use of UV lamps?
- final step of sterilization
77
What is filtration important in?
- removal of cysts/oocysts as they are tolerant to chlorine
78
What is chlorine demand? What is it also referred to as?
- amount of chlorine that reacts with organic matter, reduced ions and microorganisms
- break-point chlorination
79
What is break-point chlorination?
- consume everything that must be consumed
80
What is residual chlorine?
- "free" chlorine after microorganisms and organic matter have been treated to "break-point"
81
total chlorine added = _______ + ________
chlorine demand + residual
82
What is the most common source of infection?
- water
83
What is HPC?
- heterotrophic plate count (total coliforms)
- indicates water quality is hazardous
84
What is an indicator organism?
- associated with intestinal tract, presence indicates fecal contamination of water supply
- ex. coliform bacteria
85
What is the operational definition of coliforms?
- aerobic and facultatively anaerobic gram-negative, non-spore forming bacteria that ferment lactose with gas formation
86
What is an example of a coliform bacteria?
- E. coli
87
What are the criteria for indicators?
- must be around when suspect organisms are around (associated with polluted water)
- must be stronger than harmful pathogens (live longer)
- must have high enough numbers to detect
88
What is the most desirable characteristic in indicator organisms?
- if it reflects both human and animal fecal pollution
89
What are the two procedures used to detect and enumerate coliform bacteria?
- MPN (most probable number
- MF (membrane filter)
90
What happens during MPN and MF
- water sample filtered onto membrane and placed in a culture medium
- grey is positive
