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Fundamentals of Engineering > Water and Wastewater > Flashcards

Water and Wastewater Flashcards

1
Q

Acidity

A

ability of a solution to neutralize hydroxide, arises from CO2 release during biological activity

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2
Q

Alkalnity

A

ability of a solution to neutralize hydrogen ions

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3
Q

MCL

A

maximum contaminant level: enforceable standards set by EPA

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4
Q

Primary drinking water standards

A

derived from MCLs, continuously revised

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5
Q

Secondary contaminant standards

A

nonenforceable, based on aesthetics

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6
Q

pH

A

describes the alkalinity/acidity of a solution- the higher the hydrogen ion concentration, the higher the acidity

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7
Q

Bicarbonate (HCO3-) is the primary source of…

A

… alkalinity in natural waters

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8
Q

To express the alkalinity of a solution….

A

… all species are converted to equivalents of CaCO3

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9
Q

Hardness

A

sum of all multivalent cations (primarily Ca2+ and Mg2+), results from water contact with minerals in subsurface environments (leads to scaling)

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10
Q

Total solids

A

(TS) residue on evaporation = weight of residue/ volume of dried sample

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11
Q

Total suspended solids

A

(TSS) = weight of residue on filter/volume of filtered sample

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12
Q

Toal dissolved solids

A

(TDS) = weight of residue from filtrate/volume of dried sample

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13
Q

Total fixed solids

A

(TFS) = weight of residue after ignition/ original volume of TS sample

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14
Q

TS =

A

TFS + TVS = TSS + TDS

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15
Q

Turbidity

A

waters that have suspended solids (generally colloidal) which scatter light

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16
Q

Oxygen solubility in water is highly dependent on…

A

… temperature (the higher the temperature, the lower the DO cnc) *oxygen solubility also decreases with increasing solute cncs)

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17
Q

Biochemical oxygen demand (BOD)

A

dissolved oxygen consumed in the biological utilization of the substrate

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18
Q

Chemical oxygen demand (COD)

A

rapid test, useful for industrial waste waters where toxic compounds inhibit biological activity

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19
Q

Additional WQIs

A

nutrients, chlorine residual, heavy metals, trace organics

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20
Q

Residence time

A

time a molecule of water is present in the reactor vessel

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21
Q

Tracer

A

non-reactive chemical used to determine the hydraulic characteristics of a reactor

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22
Q

Oxidation is used in water treatment to…

A

… transform soluble Fe2+ and Mn2+ to their insoluble counterparts (can also be achieved using chlorine and potassium permanganate)

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23
Q

Coagulation

A

Adding chemicals to cause aggregates to form (reduces electrostatic repulsions present in colloidal and particle suspensions)

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24
Q

Aluminum sulfate

A

(alum) most common coagulant

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25
Softening
removing excess metallic cations (hardness) from water through the addition of hydrated lime and soda ash, causing soluble forms to precipitate as insoluble forms
26
Sedimentation
particles fall out of suspension in quiescent water
27
Terminal settling velocity (Vs)
rate at which particles move in the vertical direction
28
Stoke's law can be applied...
... in low Re scenarios
29
Overflow rate
surface settling rate, fluid velocity in the vertical direction
30
Backwashing
reversing flow of water or air to clean filter
31
Disinfection
chlorine gas used to inactivate biological contaminants, creates free available residual chlorine (hypochlorous acid and hypochlorite ions)
32
Log removal
desired amount of treatment, specific to microbial species
33
Adsorption
contaminant attaches to solid with extremely high surface area (often achieved through air stripping)
34
Henry's law
environmental contaminants have a linear partitioning relationship between the liquid and gas phase at low concentrations when the two phases are in equilibrium
35
Reverse osmosis
semi-permeable membrane restricts flow of dissolved ions in aqueous solutions, causing pure water to flow into saline solution to equilibrate, creating pressure difference (osmotic pressure). pressure can then be applied to saline side of membrane, forcing water particles back to pure water side
36
Electrodialysis
membrane selectively allows cations and anions to pass through pores- electric current is applied to a collection of alternating layers
37
Ion exchange resin
charged surface attracts undesirable ions (often metallic cations which cause hardness)- named after what type of ion they attract
38
Sludge
mixture of solids and water from presedimentation, coagulation/flocculation, filter backwashing, lime softening
39
Concentrates
wastewater generated by membrane filtration
40
Thickening
meant to increase solids content of sludge
41
Conditioning
increasing the dewaterability of sludge through the addition of chemicals
42
Dewatering
increasing solids content of sludge to greater than 8% through centrifugation, vacuum filtration, plate and frame, and bed filter press
43
Domestic wastewater
residential, commercial, institutional sources
44
Municipal wastewater
domestic + some permitted industrial wastewater
45
Industrial wastewater
high concentrations of biologically inhibiting contaminants, pretreated prior to discharge
46
Conventional WWTP
preliminary, primary settling, biological aeration, secondary clarification, tertiary treatment, disinfection, sludge processing
47
Preliminary treatment
removes large particles via screening and grit removal
48
Flow equalization
some influent is diverted to holding tank during peak flow periods and released later
49
Primary treatment
solid particles fall out of suspension in quiescent tanks via sedimentation
50
Secondary (biological) treatment
bacteria reduce BOD
51
Activated sludge
biosolids rich in bacteria from the final clarifier are returned to aeration tank
52
Mixed liquor suspended solids (MLSS)
concentration of bacteria in aeration tank
53
Solids retention time (SRT)
average length of time a single cell (solids) spends in the treatment system
54
Stabilization ponds
symbiosis between algae and aerobic bacteria cohabit with anaerobic sedimentary activity, naturally treating domestic wastewater from small populations
55
Nitrification
conversion of ammonia to nitrate
56
Denitrification
reduces nitrates to nitrogen gas, nitric oxide, and nitrous oxide
57
Phosphorus removal
removed from wastewater by precipitation with lime, alum, or ferric salt
58
Activated carbon
removes heavy metals and organic material not consumed in secondary treatment via adsorption
59
Disinfection
removal of pathogens via chlorination or UV light
60
Anaerobic digestion
hydrolysis of organic compounds to acids, followed by formation of carbon dioxide and methane

Fundamentals of Engineering (9 decks)

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