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

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)

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: 0.10 - 0.12 mg/l Intense chlorinous-like odors are systematically detected (TON exceeds the European guideline)

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 ≈ 0.6 - 0.7 ppm NH4 < 0.1 ppm DOC ≈ 0.8 ppm

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 = 5,5 4.1 0.7 pH= 7 6.1 0.7 pH= 8.5 11.9 1.0

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= 5.5 0.60 0.1 Chlorine, I= 10 Chlorine, I= 0 + chlorine pH = 7 0.53 0.13 Chlorine, I= 8 Chlorine, I= 8 (lab experiment) pH= 8.5 0.40 <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

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 90 4 6 Dichlorobromomethane 450 <2 <2 Dibromochloromethane 200 <2 <2 Bromoform 5 <5 <5 Conclusion: THM’s are far below their individual odor thresholds

ANALYSIS OF HAA’s ON LA FALAISE CHLORINATED WATER SAMPLES: COMPARISON WITH CHLORINOUS ODOR INTENSITY 1 2 3 4 5 6 7 8 9 Concentration µg/l Odor intensity DBAA Chlorinous odor intensity 3 4 5 6 7 8 9 1 Sample n°

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

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)

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

THE ANALYTICAL APPROACH FAILED TO IDENTIFY THE ODOROUS COMPOUNDS TREATMENT TESTS

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

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

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

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

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 0.0025 (2.5 l/h) V/V/h m3/m3/h 6.3

REMOVAL OF CHLORINOUS ODOR BY VIRGIN OR SATURATED GAC (from Sept. 26 to Oct. 20, 1997) Chlorinated water Residual free chlorine: 0.02 - 0.14 Chlorinous odor intensity: 8 - 12 Chlorinous taste intensity : 6 - 10 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

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)

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

USE OF ALTERNATIVE DISINFECTANTS: COMPARISON BETWEEN CHLORINE and CHLORINE DIOXIDE (August - September 1998) Raw water Residual (ppm) Taste Odor + Cl2 0.12 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

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)

EFFECT OF CHLORINATION AFTER UV DISINFECTION (August - September 1998) Raw water Residual (ppm) Taste Odor + UV 0.11 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

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