Analyze Immediately Residual Chlorine. Topics…. Background: Chlorine Chemistry Industrial Application NJAC Regulations Summary.

Analyze Immediately

Residual Chlorine

Topics….

• 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!!!