CWEA Grade I Laboratory Analyst Exam 2023
Chloride
- Major anion found in many natural waters
- Can impart salty taste in H2O
What increases concentration of chloride in wastewater
Chloride in human diet and softeners flushed into sanitary sewer system
2 most prevalent methods of measuring ...
CWEA Grade I Laboratory Analyst Exam 2023
Chloride
- Major anion found in many natural waters
- Can impart salty taste in H2O
What increases concentration of chloride in wastewater
Chloride in human diet and softeners flushed into sanitary sewer system
2 most prevalent methods of measuring chloride
argentometric and mercuric nitrate
Argentometric
Titration of sample with standard solution of silver nitrate (AgNO3)
- Indicator: Chromate ions (CrO4)
- End point: reddish silver chromate
Mercuric Nitrate
Titration with standard mercuric nitrate solution
-pH must be adjusted between 2.3 and 2.8
- Indicator: Diphenyl carbazone
- End point: Change from blue to purple in presence of mercury
Interference of Mercuric Nitrate Method
Sulfide, bromide, orthophosphate (over 30 ppm), and iodide
Why does color change in water
Presence of decaying vegetable matter, metal ions (ie. iron) or industrial and domestic
pollution
How is color measured
Measured using visual comparison method
Visual comparison method
Sample compared to standards using matched nessler tubes
- Standards prepared with solution containing cholorplatinate and cobaltous chloride
Standard units for color
One unit= color resulting from 1 mg of platinum/L
2 color reporting
True and Apparent
True color
Color from dissolved substances, determine using sample treated to remove turbidity
Apparent Color
Includes dissolved and suspended solids
Conductivity
H2Os capability to pass electrical flow
Conductivity of pure water
0
Units of conductivity
micromhos/cm
Temperature conductivity should be read at
25 degrees Celcius
How is conductivity affected
Mobility of ions, conductivity is dependent on viscosity
, Viscosity
A liquids ability to resist flow, higher the viscosity the lower the flow
Relationship of temperature and viscosity
Inverse
Acid
A compound which liberates hydrogen ions and has a pH below 7.
Alkalinity:
The measurement of a sample's capacity to neutralize acid.
Alkalinity measures
The carbonate, bicarbonate, and hydroxide ion concentration found in water
Primary reason for measuring alkalinity
Used in control of many water and wastewater unit processes
How is alkalinity measured
Titration of a sample with a standard solution of either sulfuric acid or hydrochloric acid
to predetermined pH endpoint
The phenolphthalein alkalinity of a water sample is zero if:
The pH is greater than 8.3
Atomic Weight:
The sum of the number of protons and the number of neutrons in the nucleus of an
atom.
Atomic weights of elements are found on periodic tables.
Base:
A compound which liberates hydroxide ions and has a pH above 7.
Biochemical Oxygen Demand (BOD):
The quantity of oxygen utilized in the biochemical oxidation of organic
matter under standard laboratory procedures for five days at 20° Centigrade, usually
expressed as a
concentration (e.g., mg/L). BOD measurements are used to indicate the organic
"strength" of wastewater.
Chain-of-Custody:
A legal record (which may be a series of records) of each person who had possession
of an environmental sample, from the person releasing the sample, to the person who
collected the sample, to
the person who analyzed the sample in the laboratory, to the person who witnessed the
disposal of the
sample.
Chemical Oxygen Demand (COD):
The amount of oxygen (expressed in mg/L) consumed from the oxidation
of pollutants during a specific test. As such, COD is a measure of the oxygen-
consuming capacity of the
pollutants present in wastewater. The results of the COD test are not necessarily related
to the BOD, because
the chemical oxidant responsible for utilizing the oxygen may react with substances
which bacteria do not
stabilize.
Composite Sample:
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