Transcript Analyze Immediately Residual Chlorine Topics…. • • • • Background: Chlorine Chemistry Industrial Application NJAC Regulations Summary Hold Times • 0 - 15 minutes - note time of collection & time of.

Analyze Immediately
Residual Chlorine
Topics….
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Background: Chlorine Chemistry
Industrial Application
NJAC Regulations
Summary
Hold Times
• 0 - 15 minutes - note
time of collection &
time of analysis!
Background:
• A strong oxidizing
agent
• …therefore, a very
reactive element...
• …oxidizes inorganic
& organic matter in
the water supply &
pipe distribution
systems...
Chlorine Chemistry
• Chlorine gas
hydrolyzes in water
to form hypochlorous
acid (HOCl):
Cl2 + H2O  HOCl + H+ + Cl-
• H+ ions released in the
reaction cause a
reduction in pH.
(sample is more
acidic)
More Chemistry!!!!
• Hypochlorous form of chlorine is prime
disinfecting agent
• “free available chlorine” or “free chlorine”
refers to both HOCl (hypochlorous acid) &
OCl- (hypochlorite ion) - ( portions present
in the water.
• If chlorine added to water containing
ammonia, chloramines will form….
Definition:
• Chloramines + other
chlorine-nitrogen
compounds = “free
available chlorine”
• “total residual
chlorine” (aka,
“residual chlorine”)
= free available
chlorine + combined
available chlorine.
Chlorine Produced Oxidants
(CPO)
• Synonym for total residual chlorine (TRC)
• In 1992, NJDEP established reporting level
for wastewater
• The enforceable level for permittees with
TRC or CPO effluent limits below 0.1
mg/L is 0.1 mg/L
Dechlorinating Agents
• Disinfectant water must be neutralized
before release into stream
• Common dechlorinating agents:
sulfur dioxide (SO2)
sodium bisulfite (NaHSO3)
sodium sulfite (Na2SO3)
sodium thiosulfate (Na2S2O3)
Dechlorinating Agents
• Sodium thiosulfate
(Na2S2O3) - frequently
used dechlorinating
agent
• Excessive use of other
dechlorinating agents
(sodium sulfite or
sodium bisulfite) can
cause low O2 levels in
waterways.
NJAC Regulations
• Methods: EPA 330.1 5, SM 4500-CL B
through G.
• new calibration curve
prepared intially or
quarterly
• 1 reagent blank & 5
stds.
• calibration coefficient
>0.995.
NJAC Regulations
• Lab shall verify the
calibration curve with the
calibration check
std.(CCS), daily or after
every 20 samples,
whichever is more
frequent
• CCS must have a
concentration at or near
the middle of the
concentration range of the
calibration curve.
NJAC 7:18-5.5(c)4
• Lab must record all
data used in
determining the
calibration curve
• Signed by analyst
• Record:
-date of calibration
-ID of standards.
-standard conc.
Caveats
• When using chlorine
kits…
• measuring free chlorine 1 minute test….
• Versus a 2 - 3 minute test
for measuring total
chlorine (follow mfg.
instructions)
• Wastewater reporting limit
(RL) < 0.1ppm, per
NJDEP 1992 letter to
permittees .
Summary
• Chlorine is useful in:
* water treatment - to maintain
a residual to kill bacteria
* waste water treatment plants chlorine is used to destroy
pathogens, then chlorine is
removed from water prior to
discharge into waterway
• Measurement of residual
chlorine gives a snapshot of the
chlorine present in water, which
can act as an oxidant & which
can be hazardous to aquatic life.
Thank you...
...for your
patience, time
and attention
today!!!