CEE 311
Fall 2009
Dr. Kauser Jahan, P.E.
LABORATORY 6: BREAKPOINT CHLORINATION
Objectives:
 measure the chlorine residual (free and total) at different chlorine doses for a
given water sample;

generate a chlorine breakthrough curve, and

determine the dose required for break point chlorination.
Sample Source:
Synthetic ammonia water.
Background: When DPD (N,N-diethyl-p-phenylenediamine) is added to a sample
containing free chlorine residual, an instantaneous reaction occurs, producing a red
color. If a small amount of iodine is then added to the sample, monochloroamine reacts
to produce iodine, which in turn oxidizes more DPD to form additional red color. The
intensity of red color can be analyzed either by titration or directly by colorimetric
analyses.
Materials: Hach DPD Chlorine Kits, Glass Containers, Ammonium Hydroxide
(NH4OH), Clorox Bleach
Method: Steps 1 through 6 will already be completed for students.
1. Prepare a stock chlorine solution from Clorox bleach. Add 6mL of Clorox to 1
liter of DI water.
2. Add 2 mL of stock chlorine solution to 300 mL of DI water to have a 150:1 dilution
ratio.
3. Use the HACH DPD Chlorine kits and measure the free and total chlorine
concentrations. MAKE SURE TO HAVE A BLANK WITH DI WATER!!
4. Determine the actual concentrations of free and total chlorine of the stock
solution by multiplying results by 150.
5. Prepare an ammonia water solution.
6. Pour 50 mL of ammonia water into a BOD Bottle.
DO NOT FOOL AROUND
WITH CLOROX BLEACH.
IT IS CORROSIVE!!
7. Add chlorine stock solution as indicated in Table 1 to each container.
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Table 1: Chlorine Dose in Bottles
Container #
1
2
3
4
5
6
7
8
9
Chlorine Dose
mg/L
2
4
6
8
10
12
14
16
18
Stock Added mL
8. Mix chlorine with the ammonia water samples. Place the bottles in the dark for
45 minutes.
9. Analyze each bottle for total and free chlorine residuals using the HACH DPD
Chlorine kits. You will need to dilute the samples so that they are within range of
the test kits.
SAFETY: The
ban on horseplay needs no explanation.
Gloves, aprons and goggles are to be worn during the sample handling process.
SAMPLE DATA SHEET
All data must be recorded in your laboratory notebooks. Yellow pages must be included with
the laboratory report.
TEAM LABORATORY REPORT
(Hand written reports will not be accepted. Use computer spreadsheets and word
processors as necessary. Sample calculations should be presented on
engineering paper.)
Results
1. Report raw data in a tabular form.
2. Include Excel worksheet showing calculations with formulae and plots if applicable.
3. Report results on a separate sheet of paper with appropriate units.
Include in Discussion
1. Define free, combined and total chlorine residual.
2. What is break point chlorination?
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3. What are the reactions that lead to the formation of THMs and HAAs?
4. What are the factors that affect disinfection efficiency of chlorine?
5. Name three major ways of disinfection.
Useful References/Sites
http://www.hach.com/Spec/SCOD.htm
APHA, AWWA, WPCF (1995) Standard Methods for the Examination of Water
and Wastewater, APHA, Washington, 19th edition.
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