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WW Quiz 3 Questions & Answers
If you want to know the organic content or strength of a wastewater sample within a few hours of collecting the sample, you should test for:
a) pH
b) BOD
c) COD
d) Fixed SS
e) Total SS - ANS-c) COD
Preliminary and Primary Treatment - ANS-To remove settleable and floatable solids
Bar Screens, Grit Removal, Primary Clarifier
Secondary Treatment - ANS-To remove BOD and inorganic pollutants (NH3 and phosphorus)
Biological treatment
Aeration Tank, Final Clarifier
Sludge Treatment - ANS-To dispose residual solids
Thickener-Clarifier, Anaerobic Digester, Vacuum Filter
Primary Clarifier Removal - ANS-50-70% TSS removal
25-40% BOD 5 Removal
Free chlorine reacts with NOM in water to form which of the following disinfection byproducts:
a) Trihalomethanes
b) Haloacetic acids
c) Nitrosamines
d) NDMA
e) All of the above (i.e., a to d)
f) a and b only - ANS-f) a and b only
What is the most potent form of chlorine for inactivating pathogens?
a) HOCl
b) OCl-
c) NH2Cl
d) NHCl
e) NCl3 - ANS-a) HOCL
Why is a wavelength of around 250 nm used for UV disinfection?
a) Light at that wavelength is strongly absorbed by cell membranes
b) Light at that wavelength is strongly absorbed by DNA
c) Light at that wavelength is strongly absorbed by cell walls
d) None of the above - ANS-b) Light at that wavelength is strongly absorbed by DNA
If the smallest grit has vs = 4 ft/min and vscour = 35 ft/min, and the organic particles have vscour = 11 ft/min, which grit chamber design will work for a flow of Q = 1000 ft3/min (L = Length, W = Width, and D = Depth)? [ignore any safety factor: i.e., SF = 1]
a) L = 6 ft, W = 42 ft, D = 9 ft
b) L = 42 ft, W = 6 ft, D = 9 ft
c) L = 25 ft, W = 6 ft, D = 9 ft
d) L = 25 ft, W = 5 ft, D = 5 ft
e) L = 50 ft, W = 5 ft, D = 5 ft - ANS-b) L = 42 ft, W = 6 ft, D = 9 ft
Q/vs= LxW
Bar Racks - ANS-remove large objects
0.25-1.5 in between bars
1.5-3 ft/s
Flow Equalization - ANS-seasonal changes cause flow rate changes, flow equalizer keeps flow steady throughout the year
Comminutors and Grinders - ANS-like a garbage disposal, consists of a screen or slotted basket, a rotating or oscillating cutter and a stationary cutter
Downstream of grit chamber
Grit Chamber - ANS-Grit: hard abrasive inorganic particles, e.g., sand, gravel, broken glass
Grit has a relatively high density (1.5-2.7 g/cm3 ) and settles easily
Horizontal Flow Grit Chamber - ANS-important parameters: Aplan and horizontal flow velocity vH
Horizontal Flow Velocity - ANS-should be 0.3 m/s
constant and controlled by either a parshall flume or proportional weir that is placed at the downstream end of the grit chamber
Scouring - ANS-the process that horizontal water flow resuspends the settled sediments
Design parameters - ANS-To settle the particle before it leaves the chamber, the settling velocity should be equal to critical overflow rate
Vh parameters - ANS-5.6 cm/s<Vh<17.7 cm/s
Minimum vh - ANS-If organic particle (SG=1.1) is the lightest thing to be resuspended, Vscour for scouring organic particle would be the minimum of Vh.
Aerated grit chamber - ANS-pipe to create a rolling or spiral flow and particle travel pattern, compared to straight line in the horizontal settling tank
Remove similar percent of grits but with a much shorter chamber
No flow control required.
odor and grease removal.
t= 3 min
How do bacteria sustain life and function? - ANS-extract energy, electrons, elements from the environment by catalyzing redox reactions
substrate catabolism products - ANS-energy production+electrons+waste
substrate anabolism products - ANS-cell biomass
catabolism - ANS-conversion substrates to produce energy
anabolism - ANS-utilize substrates to synthesize cell constituents, requires energy, carbon source, N, P, S and trace elements
Electron donor - ANS-oxidized, valence increases
Electron acceptor - ANS-reduced, valence decreases
organotrophs energy source - ANS-organic BOD
denitrification - ANS-organic + NO3- --> CO2 + H2O + N
electron donor: organic BOD
electron acceptor: NO3-
carbon source: organic BOD
product: CO
anaerobic heterotrophic
facultative
Anammox - ANS-NH3 + NO2- --> N
electron donor: ammonia
electron acceptor: NO2-
anaerobic autotrophic
autotrophic - ANS-electron donor inorganic
heterotrophic - ANS-electron donor organic
fermentation - ANS-anaerobic heterotroph
breaks down BOD in the absence of oxygen and nitrate to generate short-chain fatty acids that are used for methanogensis
