1. CHLORINOUS ODORS WITHOUT CHLORINE:
SEARCH FOR THE ORIGINS AND TREATMENT SOLUTIONS
A. Bruchet, C. Hochereau
LYONNAISE DES EAUX - CIRSEE
38, rue du Président Wilson
78230 Le Pecq - France

2. CHANGE IN RAW WATER QUALITY
INTRODUCTION
The LA FALAISE ground water (West of Paris) has had a complex history of taste and odor episodes
In 1990, a study could partially attribute the T&O to the formation of iodoforms during chlorination. It was shown that chlorine dioxide could reduce the iodoforms (a factor 7) and decrease the taste to acceptable levels
CHANGE IN RAW WATER QUALITY
In 1995, the facility had to be shut down due to unacceptable chlorinous-like odors (--> many consumer complaints)

3. CHARACTERISTICS OF LA FALAISE FACILITY
A single borehole, depth = 35m, rural area
Flow rate: 200 m3/h
Disinfection with gaseous chlorine
150 m3 storage tank
Residual chlorine: mg/l
Intense chlorinous-like odors are systematically detected (TON exceeds the European guideline)

4. EVOLUTION OF CHLORINE DEMAND BETWEEN 1990 and 1997
0,8 , 7
Free Cl mg/l
Total Cl mg/l
Break-point= 1.2 mg/l
Free Cl mg/l
Total Cl mg/l , 6
0,6 , 5
Break-point= 0.5 mg/l
Residual chlorine mg/l , 4
Residual chlorine mg/l
0,4 , 3 , 2
0,2 , 1
0,5
1,0
1,5
2,0 , 2 , 4 , 6 , 8
Chlorine dose ppm
Chlorine dose ppm
NH4= 0.15ppm
DOC ≈ ppm
NH4 < 0.1 ppm
DOC ≈ 0.8 ppm

5. Compared chlorination kinetics at 3 pH
(La Falaise raw water - Applied dose = 0.85 ppm) , 7 , 6 , 5 P H = 5 . 5 , 4
Chlorine residual mg/l P H = 7 , 3 P H = 8 . 5 , 2 , 1 5 1 1 5 2 2 5 3
Time (hours)
Apparent kinetic constant
K1 (rapid).10-3 K2 (slow).10-3
min-1 min-1
pH = 5,
pH=
pH=

6. FLAVOR PROFILE ANALYSIS AS A FUNCTION OF TIME and pH
(Applied dose = 0.85 ppm) 1 2
Residual free Flavor profile analysis
chlorine (mg/l) after 24 hours 1
T= 0 T= 25h Taste Odor
Raw water pH= Chlorine, I= 10 Chlorine, I= 0
+ chlorine pH = Chlorine, I= 8 Chlorine, I= 8
(lab experiment) pH= <0.05 Chlorine, I= 6 Chlorine, I= 4
Chlorinated pH= 7 Chlorine - Chlorine -
well water Plastic, I= 8 Plastic, I= 10 8
T or O intensity 6 4
Evolution of odors
Evolution of taste
0.06 2 2 4 p 6 8 1 1 2
Conclusion : H
T&O intensity much higher than expected from residual chlorine concentration
Chlorine T&O decrease with increasing pH

7. ANALYSIS OF THM’s BY HEAD-SPACE GC-ECD IN LA FALAISE CHLORINATED WATER
THM Odor threshold Concentration
(45°C, µg/l) (µg/l)
April 97 June 97
Chloroform
Dichlorobromomethane 450 <2 <2
Dibromochloromethane 200 <2 <2
Bromoform 5 <5 <5
Conclusion: THM’s are far below their individual odor thresholds

8. ANALYSIS OF HAA’s ON LA FALAISE CHLORINATED WATER SAMPLES: COMPARISON WITH CHLORINOUS ODOR INTENSITY1 2 3 4 5 6 7 8 9
Concentration µg/l
Odor intensity
DBAA
Chlorinous odor intensity 3 4 5 6 7 8 9
Sample n°

9. ANALYSIS OF ALDEHYDES 30 25 20 15
Chlorinous odor intensity
Concentration µg/l
Methylglyoxal 10
Glyoxal
Decanal 5
Hexanal
Pentanal
Acetaldehyde
Formaldehyde
ECH 3
ECH 4
ECH 5
ECH 6
ECH 7
ECH 8
ECH 10
ECH 11
Me-glyoxal, glyoxal, acetaldehyde and isobutyraldehyde were mixed in reference water according to the concentrations found in water
No taste or odor detected

10. ANALYSIS BY CLSA / GCMS 01 Alkane 02 Trichloroethane
03 Trichloromethane
04 Alkane
05 Benzene
06 Cycloalkane
07 Trichloroethene
08 Cycloalkane
09 Bromodichloromethane
10 Dimethyldisulfide
11 Toluene
12 Tetrachloroethene
13 Alkane
14 Ketone
15 Dibromochloromethane
16 Alkohol
17 C6-Chloroalkane
18 Alkyls benzene - C2
19 Styrene
20 Bromoform + hydroxy methyl
4 pentanone
21 Aldehyde
22 Siloxane
23 Alkyl benzene - C3
24 Terpene
25 Dichlorobenzene
26 Aldehyde
27 C8-Chloroalkane (IS)
28 Dibromoiodomethane
29 Siloxane
30 Aldehyde
31 Alkene
32 Dimethyl ester of carbonotrithioic acid
33 Aldehyde
34 C-10 Chloroalkane (IS)

11. COMPARISON BETWEEN TOTAL CHLORINE and THRESHOLD ODOR NUMBER
(ammonia constantly <0.1 mg/l in raw water) 3 6 2 5 5 2 4
Total chlorine (µg/l)
Total chlorine (µg/l)
T O N 1 5 3
T O N 1 2 5 1
08/03/95
08/13/95
08/23/95
09/02/95
09/12/95
09/22/95

12. THE ANALYTICAL APPROACH FAILED TO IDENTIFY THE ODOROUS COMPOUNDS
TREATMENT TESTS

13. EFFECT OF REDUCING AGENTS ON CHLORINE T&O
pH Dechlorination agent Chlorinous T&O intensity
pH= 5.5 Before dechlorination 10
pH= sodium thiosulfate 0
pH= 7 Before dechlorination 10
pH= sodium thiosulfate 0
pH= ammonium chloride 5
pH= 7 Before dechlorination 8
pH= 7 + ammonium chloride 3

14. SHOCK CHLORINATION
After development of the chlorinous odors, the chlorinated water has been submitted to “shock chlorination” using a chlorine dose equal to ten times the amount of total chlorine.
This type of treatment, which is usually successfull in swimming-pools to destroy combined chlorine, failed to eliminate the chlorinous odors
Odorous molecules(s) involved are probably in a very oxidized form

15. PILOT STUDY WITH NEW AND SATURATED GAC (September 1997)
Saturated GAC column
New GAC column
Sampling point
Pump
GAC filtered water
Final disinfection Cl2 or ClO2

16. TREATMENT STRATEGY
Apply a low disinfectant dose to ensure a minimum residual on the distribution system
Attempt to destroy or adsorb odorous compound(s) by GAC
Develop the chlorinous T&O with Cl2
Raw
water

17. GAC OPERATING CONDITIONS
(CHEMVIRON F400)
Column internal diameter m 0.025
GAC height m 0.8
Filtration rate m/h 5
EBCT min 9.6
Flow rate m3/h (2.5 l/h)
V/V/h m3/m3/h 6.3

18. REMOVAL OF CHLORINOUS ODOR BY VIRGIN OR SATURATED GAC
(from Sept. 26 to Oct. 20, 1997)
Chlorinated water
Residual free chlorine:
Chlorinous odor intensity:
Chlorinous taste intensity :
Virgin GAC
Saturated GAC
Cl2 < 0.02
No taste
No odor
Cl2 < 0.02
No chlorinous T&O
“Humus-like” T&O I= 2-4

19. EFFECT OF RECHLORINATION AFTER GAC
Chlorinated
Water filtered
with virgin GAC
No taste
No odor
+ 0.3 ppm Cl2
+ 0.2 ppm ClO2
Residual chlorine: 0.02 ppm
Swimming-pool, astringent taste (I= 8)
Swimming-pool odor (I= 8)
Residual ClO2: 0.04 ppm
Swimming-pool taste (I= 6)
Undetermined odor (I= 6)

20. Once the chlorinous T&O have been developed, they are easily removed by GAC (probably by reduction rather than by adsorption)
Unfortunately, the reaction(s) involved are reversible and the odors reappear as soon as the water is rechlorinated (low Cl2 or ClO2 dose) to maintain a residual in the distribution system.
Chlorination - dechlorination - rechlorination strategy failed

21. USE OF ALTERNATIVE DISINFECTANTS: COMPARISON
BETWEEN CHLORINE and CHLORINE DIOXIDE
(August - September 1998)
Raw water Residual (ppm) Taste Odor
+ Cl Chlorine, musty I= 6-8 Chlorine I= 6
Swimming-pool
0.02 Chlorine + ? I= 6 Chlorine I= 8
Tingling
Raw water Non measurable Muddy I= 6 Chlorine I= 2-4
+ ClO2 (contact time = 10 days) Swampy

22. USE OF ALTERNATIVE DISINFECTANTS : UV
UV filter Karadyn
Description: UV irradiation chamber
water content: 1 liter
contact time: 56 seconds
UV dose: 340 mW.s/cm2
Taste Odor
Raw water Earthy I= 2 No odor
+ UV
(September 14, 1998)

23. EFFECT OF CHLORINATION AFTER UV DISINFECTION
(August - September 1998)
Raw water Residual (ppm) Taste Odor
+ UV Chlorine I= 4-6 Chlorine I= 6-8
+ Cl2 Swimming-pool Swimming-pool
0.03 Chlorine I= 4 Chlorine I= 6-8
+ undetermined undetermined
Raw water Non measurable Oxidant I= 4 Chlorine I= 4-6
+ UV Astringent undetermined
+ ClO2 Tingling
Chlorinous odors reappear even at low disinfectant doses

24. CONCLUSIONS VERY OXIDIZED FORM
Formation of chlorinous-like odors which cannot be attributed to free or combined chlorine (several sites)
The odorous molecules remain unknown. Classical DBP’s do not seem to be involved. They are easily reduced but difficult to further oxidize
VERY OXIDIZED FORM
The odor is removed by reducing agents (sodium thiosulfate, GAC) but reappears during post-chlorination required to maintain a residual in the DS.
ClO2 does not solve the problem, nor does shock chlorination
Disinfection by UV alone seems to avoid the development of the odors, provided no chlorinous disinfectant is used afterwards