Water Quality Concept Check L10 Flashcards
(23 cards)
The units of a rate constant depend on the order of the reaction. (True/False)
True
A negative reaction rate term (-R) means that the chemical is being consumed/generated in the reaction.
Consumed
A conservative substance undergoes reaction. (True/False)
False
Theta, called the ____________ describes the average time fluids spend in a reactor
Hydraulic resonance time
The PFR model may be applied to natural systems such as rivers as well as engineered systems.
True
A spike of contaminant moves through a CSTR/PFR as a plug, not mixing with the fluid in front of or behind of it.
PFR
Reaction kinetics describe the rate at which a reaction occurs (true/false)
True
As in a CSTR, the pollutant concentration in a pfr is always homogenous throughout the reactor. (True/false)
False
What is the overall order of the reaction described in the following rate law? R=k[C6H6][NO3-]2
Third order
Oxygen demand is
The amount of oxygen consumed by biota or reacted with chemicals
What is the max amount of oxygen in clean water and why?
9 mg/l because of Henry’s law
How does temperature affect DO?
Causes DO saturation level to decrease
How dues salinity affect DO?
Causes DO saturation level to decrease
How does elevation affect DO?
The partial pressure of oxygen decreases as elevation increases, so the DO saturation level decreases
How does turbulence affect DO?
A turbulent stream will replenish DO quickly while a slow, sluggish stream will replenish DO slowly
What processes affect the dissolved oxygen concentration in water?
1) oxygen transfer from atmosphere
2) aerobic biodegradation of organic
3) microbial nitrification
4) photosynthesis
What depletes dissolved oxygen in water?
1) aerobic biodegradation of organics {organics converted to CO2}
2) microbial nitrification {ammonia converted to NO3-}
What is theoretical oxygen demand (ThOD)?
Amount of O2 theoretically nessary to oxidize contaminant
What is biochemical oxygen demand (BOD)?
Amount of O2 necessary if oxidation carried out by bacteria
Is BOD or ThOD bigger?
BOD is always less than ThOD because some glucose is incorporated into new cells
What is carbonaceous oxygen demand?
Oxygen required to oxidize C compounds
What is nitrogenous oxygen demand?
Oxygen required to oxidize N compounds
How do we measure oxygen demand for a water sample?
Procedure for BOD test:
1) take sample of water
2) add microorganisms
3) measure DO consumption by microorganisms over 5 days
Parameters: temperature 20°, conduct test in dark, need at least 2mg/L change in DO over 5 days
