LAB ANALYST I/II – CWEA DETAILED EXAM
MATERIAL (COMPREHENSIVE PRACTICE
QUESTIONS & ANSWERS)
Celcius
Fahrenheit
(F-32)5/9
(C+32)9/5
HPC
water media bath
time for incubation and temp
unit
45C 3 hrs hold time
48 ± 3hr at 35 ± .5C
CFU/ml
Precision
a measurement of how close a series of measurements are to one another
Accuracy
how close a measurement is to the true value
Electrical Fire
Unplug and sodium bicarbonate
Analytical Balance
A device for determining mass that gives highly accurate measurements
Top loading balance
used to determine mass; not as precise as an analytical balance
Triple beam balance
instrument used to measure mass, less sensitive than top loading
,Coliform characteristics; gram? shape?
E Coli is an indicator organism because..
gram-negative, rod shaped bacteria present in intestines', includes E coli and other sp
indicator because the presence indicates conditions are right for harmful bacteria
Always add - to -
Acid to water
Spectrometer definition
UV/Visible spectroscopy is based on what principle?
In atomic absorption, atoms must be x to absorb light at its characteristic wavelength
a device that spreads light into its different colors
Beer’s/Lambert’s law; absorbance is proportional to concentration
reduced to their ground-state
rounding off
.5 = keep, <.4 same, >.6 round up
sig fig rules
use the smallest amount of decimal places;
non zero digits always sig
any zeros b/t sig digits are sig
trailing or final zero in decimal portion only are sig
BOD
total =
vol, bottle, temp, time
storage ph? pretreatment?
method
If DO present, what color will floc turn after alkaline iodide-sodium azide solution is
added? No DO?
what colors during titration?
,formula?
after 5 day incubation, BOD sample should have a DO depletion of at least? and blank
should never exceed?
CBOD, 2-chloro-6-trichlormethyl pyridine (TCMP) suppresses
if >9.0 mg/L DO at 20C, you should
what sugar compound used?
units
interferences
calculation for seeded & unseedd
total = Carbenous, soluble, nitrogenous
1000 ml, p/g, 4C, 48h
neutralized 6.5-7.5, dechlorinated residual Cl, .025 N sodium sulfite
method
5 d 20 ± 1C incubation ±6h
brown with DO, white w/o DO
brown → straw yellow → blue → clear
(DOi-DOf)/(sample vol/bottle vol)
take 2.0 mg/L, leave 1.0, blank must not deplete more than 0.2 mg/L DO
(carbonaceous BOD) suppresses nitrification
agitate or aerate the sample at 20C
glucose
mg/L DO
interferes with algae, probe membrane…bio based test cannot control all variables
sample labels should include
sample number, sample type, name of collector, date/time of collection, place of collection, and
sample preservative
mg/L to lb/day
feed rate (lb/day)=dosage(mg/L) x flow rate (mgd) x 8.34
, composite sample
collection of indiviual samples obtained at reguular intervals based on flow or time (combined
porportionally)
grab sample
sample taken from a waste stream without regard to flow, over a period of time not to exceed 15
minutes
COD CHEMICAL OXYGEN DEMAND
summary
vol, bottle, acidify and temp, time
standard?
method?
1. open
2. closed
what is wrong with a COD sample turns green in reflux?
wavelength spec
calculation
units
haz waste produced
interferences
COD=BOD=TOC Correlation?
Dichromate ions oxidize organics in sample to produce chromic ions Cr3+
50 ml, p/g, h2so4 to ph<2, 4c, 7 days
std: potassium dichromate K2Cr2O7/potassium acid phthalate
method
Open: K2Cr2O3 and titrated with FAS blue green to red brown
Closed: dichromate oxidized ferrous ions, blue green to red brown
(ferrous ions no longer oxidized by dichromate, phenathroline forms red complex. takes end
point to first sharp color change blue green to reddish brown)
MATERIAL (COMPREHENSIVE PRACTICE
QUESTIONS & ANSWERS)
Celcius
Fahrenheit
(F-32)5/9
(C+32)9/5
HPC
water media bath
time for incubation and temp
unit
45C 3 hrs hold time
48 ± 3hr at 35 ± .5C
CFU/ml
Precision
a measurement of how close a series of measurements are to one another
Accuracy
how close a measurement is to the true value
Electrical Fire
Unplug and sodium bicarbonate
Analytical Balance
A device for determining mass that gives highly accurate measurements
Top loading balance
used to determine mass; not as precise as an analytical balance
Triple beam balance
instrument used to measure mass, less sensitive than top loading
,Coliform characteristics; gram? shape?
E Coli is an indicator organism because..
gram-negative, rod shaped bacteria present in intestines', includes E coli and other sp
indicator because the presence indicates conditions are right for harmful bacteria
Always add - to -
Acid to water
Spectrometer definition
UV/Visible spectroscopy is based on what principle?
In atomic absorption, atoms must be x to absorb light at its characteristic wavelength
a device that spreads light into its different colors
Beer’s/Lambert’s law; absorbance is proportional to concentration
reduced to their ground-state
rounding off
.5 = keep, <.4 same, >.6 round up
sig fig rules
use the smallest amount of decimal places;
non zero digits always sig
any zeros b/t sig digits are sig
trailing or final zero in decimal portion only are sig
BOD
total =
vol, bottle, temp, time
storage ph? pretreatment?
method
If DO present, what color will floc turn after alkaline iodide-sodium azide solution is
added? No DO?
what colors during titration?
,formula?
after 5 day incubation, BOD sample should have a DO depletion of at least? and blank
should never exceed?
CBOD, 2-chloro-6-trichlormethyl pyridine (TCMP) suppresses
if >9.0 mg/L DO at 20C, you should
what sugar compound used?
units
interferences
calculation for seeded & unseedd
total = Carbenous, soluble, nitrogenous
1000 ml, p/g, 4C, 48h
neutralized 6.5-7.5, dechlorinated residual Cl, .025 N sodium sulfite
method
5 d 20 ± 1C incubation ±6h
brown with DO, white w/o DO
brown → straw yellow → blue → clear
(DOi-DOf)/(sample vol/bottle vol)
take 2.0 mg/L, leave 1.0, blank must not deplete more than 0.2 mg/L DO
(carbonaceous BOD) suppresses nitrification
agitate or aerate the sample at 20C
glucose
mg/L DO
interferes with algae, probe membrane…bio based test cannot control all variables
sample labels should include
sample number, sample type, name of collector, date/time of collection, place of collection, and
sample preservative
mg/L to lb/day
feed rate (lb/day)=dosage(mg/L) x flow rate (mgd) x 8.34
, composite sample
collection of indiviual samples obtained at reguular intervals based on flow or time (combined
porportionally)
grab sample
sample taken from a waste stream without regard to flow, over a period of time not to exceed 15
minutes
COD CHEMICAL OXYGEN DEMAND
summary
vol, bottle, acidify and temp, time
standard?
method?
1. open
2. closed
what is wrong with a COD sample turns green in reflux?
wavelength spec
calculation
units
haz waste produced
interferences
COD=BOD=TOC Correlation?
Dichromate ions oxidize organics in sample to produce chromic ions Cr3+
50 ml, p/g, h2so4 to ph<2, 4c, 7 days
std: potassium dichromate K2Cr2O7/potassium acid phthalate
method
Open: K2Cr2O3 and titrated with FAS blue green to red brown
Closed: dichromate oxidized ferrous ions, blue green to red brown
(ferrous ions no longer oxidized by dichromate, phenathroline forms red complex. takes end
point to first sharp color change blue green to reddish brown)
