Effect of Cyanuric Acid on Disinfection - Another … of... · disinfection, Official Report of the Nassau County Department of Health, 1971, Mineola, NY. Favero, M. S., ... There

© 2009 Arch Chemicals 4/15/2011 Confidential Page 1

Effect of Cyanuric Acid on Disinfection Andersen, J. R., “The influence of cyanuric acid on the bactericidal effectiveness of chlorine,” 1963, Ph.D. Dissertation, University of Wisconsin.

Estimated time (minutes) required for 99% kill of S. aureus at pH 7.0, 20 C in chlorine demand free water.

Cl, ppm 0 ppm CYA 25 ppm CYA 50 ppm CYA 100 ppm CYA

0.25 0.5 11.0 14.9 23.7

0.50 <0.25 4.7 7.0 10.8

1.00 <0.25 1.9 3.5 4.9

S. faecalis data is also presented (see following AJPH article).

Andersen, J. R., A study of the influence of cyanuric acid on the bactericidal effectiveness of chlorine, American Journal of Public Health, 1965, 55(10), 1629-1637.

Estimated time (minutes) required for 99% kill of S. faecalis at pH 7.0, 20 C in chlorine demand free water.


0.25 0.3 7.2 11.5 21.7

0.50 <0.25 3.2 4.7 10.2

1.00 <0.25 1.6 2.4 4.1

Beckett, G. et al Pseudomonas Dermatitis/Folliculitis Associated with Pools and Hot Tubs --- Colorado and Maine, 1999-2000, MMWR, 12-8-00, 2000, 49(48), 1087-1091.

No CYA data, but the following statement was made in the editorial note: ‘However, cyanuric acid, which is used to reduce chlorine loss as a results of ultraviolet light exposure, is not recommended for indoor pools or hot tubs (5,6) and is prohibited in two states (7); adding this chemical reduces the antimicrobial capacity of free chlorine (8).’ 5. Williams, KG. The aquatic facility operator manual. Hoffman Estates, Illinois: National Recreation and Park Association, 1995. 6. CDC. Suggested health and safety guidelines for public spas and hot tubs. Washington, DC; US Department of Health and Human Services, Public Health Service, 1985, DHHS publication no. (CDC)99960. 7. Johnson K, Bittenbring C, Bruya L, Richwine M, Youngblood S. The encyclopedia of aquatic codes and standards. Ashburn, Virginia: National Recreation and Park Association, 1999. 8. Fitzgerald, G. P., DerVartanian, M. E. Pseudomonas aeruginosa for the evaluation of swimming pool chlorination and algicides, Applied Microbiology, 1969, 17(3), 415-421.

Black AP, Keirn MA, Smith JJ Jr, Dykes GM Jr, Harlan WE. The disinfection of swimming pool water. II. A field study of the disinfection of public swimming pools, Am J Public Health Nations Health. 1970 Apr; 60(4):740-50.

Field survey of 193 public pools. “Of the 28 pools containing chlorine residual stabilized with cyanuric acid, 18 or 64 per cent were coliform-free….all but one of these contained 1.0 mg/l or more” free available chlorine. “Of the 55 pools containing at least 0.3 mg/l of free available chorine, 45 or 82 per cent contained no coliforms….”

Brady, A. P., Sancier, K. M. Sirine, G. Equilibria in solutions of cyanuric acid and its chlorinated derivatives, J. Am. Chem. Soc., 1963, 85, 3101-3104. Brown, James C., Paul B. Stevens, Eric W. Mood, Chemical and microbial water quality constituents of 30 public spas: A cross-sectional study, presented at NEHA conference, Las Vegas, 6-23-85.

Quote from abstract:


Spas disinfected with chorine compounds without isocyanurates had significantly better bacteriological results, at lower free chlorine residuals and higher bather loads; as well as significantly lower oil & grease and Kjeldahl nitrogen concentrations than spas using chlorine containing isocyanurates.

Parameter With CYA Without CYA

pH 7.31 7.40

Temp 100.38 98.2

ORP, mV 642.54 677.0

TDS,ppm 402.58 1603.6

FAC, ppm 6.74 3.81

TC, ppm 8.73 5.26

Total alkalinity, ppm 81.83 121.0

Ca, ppm 74.75 194.0

CYA, ppm 228.42 0.0

Turbidity, ntu 0.57 0.30

Standard Plate Count, /ml 341.92 31.2

Total Coliform, /100 ml 0.25 0.0

Fecal coliform, /100 ml 0.21 0.00

Pseudomonas aeruginosa, /100 ml

395.75 18.8

COD, ppm 76.46 63.3

Oil&grease, ppm 102.68 11.24

Nitrate nitrogen, ppm 0.71 1.2

Kjeldahl nitrogen, ppm 34.50 3.21

Butterfield, C. T., Wattie, E., Negregian, S. and Chambers, C. W., Influence of pH and Temperature on the Survival of Coliforms and Enteric Pathogens When Exposed to Free Chlorine, Public Health Repts, 53, 1837-1866, (1943).

Data for ecoli, effect of pH on kill time. He also has articles on chlorine and chloramines in the same journal in 1946 and 1948.

Canelli, E., Chemical, bacteriological, and toxicological properties of cyanuric acid and chlorinated isocyanurates as applied to swimming pool disinfection: A review, American Journal of Public Health, 1974, 64(2), 155-162.

No new data, Canelli reviews data from Robiton, Stuart, Kowalski, Swatek, Donohue and Fitzgerald.

Carlsson, Fritz, Chemical aspects of the use of cyanuric acid stabilization of chlorinated swimming pool water, Water Sewage and Effluent, 1994, 14(1), 23-28.

No new data, review summarizes that cyanuric acid may slow down disinfection times, but the effect is insignificant compared to the effect of contaminants in the water.

Carlsson, Fritz, Environmental and human health aspects of the use of cyanuric acid stabilization of swimming pool water, A review of the facts from the published literature, Water Sewage and Effluent, 1994, 14(4), 33-37.

No new data, review. Section on overstabilization is repeat of Carlsson 1994 14(1).

Centers for Disease Control and Prevention and U.S. Department of Housing and

Urban Development. Healthy housing reference manual. Chapter 14. Atlanta: US


Department of Health and Human Services; 2006.

http://www.cdc.gov/nceh/publications/books/housing/housing.htm#CONTENTS

Table 14.4 has CYA max set at 100 ppm. Ditzel, R. G. , Matzner, E. A., Symes, W. F. New data on the chlorinated cyanurates, Swimming Pool Age, 1961, 35(10), 26-30.

Does not give details of method (same as Fitzgerald 1959). E. coli 18,000 /ml initial at pH 7.4. Thousands of organisms remaining per ml after 10 min and 20 min.

Chemical Cl, ppm Sample numbers

CYA, ppm 10 min 20 min

NaOCl 0.55-0.56 1,2 0 14-15 8.7-10

KDCC 0.56 7 0 12 2.2

KDCC 0.49 11 50 16 7

KDCC 0.52-0.55 12,13 50 15-18 2.2-6.1

KDCC 0.56-0.57 16,17 100 13-16 0.7-1.5

KDCC 0.80-0.86 8,9 0 8.5-17 0-1.9

KDCC 0.86 14 50 - 0

KDCC 0.81-0.84 18,19 100 10-11 0

NaOCl 0.92 3 0 8* 0

NaOCl 1.00 4-6 0 5.5-6.5 0

KDCC 1.00 10 0 5 0

KDCC 0.96 15 50 6 0

Only ~50% reduction of E coli with 1 ppm NaOCl for 10 minutes?

Donohoe, G. B., Mulligan, J. F. 1970 Field study of cyanuric acid as applied to swimming pool disinfection, Official Report of the Nassau County Department of Health, 1971, Mineola, NY. Favero, M. S., C. H. Drake, and G. B. Randall. 1964, Use of staphylococci as indicators of swimming pool pollution. U. S. Public Health Reports, 79:61-70.

Pool K is a small private pool with a very light load that employed sodium dichloroisocyanurate as a pool disinfectant. It is not surprising that with the very light bathing load there were few staphylococci, enterococci, or Streptococcus salivarius, but coliform bacteria were as frequent as in pools with heavy use. The most surprising finding was the frequent presence of the potential pathogen, P. aeruginosa, which in laboratory studies was much more susceptible to free chlorine than the coliform bacteria. Also, the total counts tended to be high for no obvious reason. These data suggest that this disinfection system, which is claimed to release free chlorine, does not have as great an effect on P. aeruginosa and some other types of bacteria as does free chlorine derived from hypochlorites or gaseous chlorine. Private pool G used calcium hypochlorite granules for half of the 1961 bathing season. Because adequate free chlorine residuals could not be maintained, the operator changed to sodium dichloroisocyanurate. Although the apparent free chlorine residuals were raised and could be maintained for long periods of time, the sanitary quality of the pool water did not improve. The total count increased, as did the concentrations of both the staphylococci and P. aeruginosa. As stated previously, P. aeruginosa were seldom found in pools which employed gaseous chlorine or hypochlorites and were maintained at moderate chlorine residuals. In this study it was found that at free chlorine concentrations of more than 0.5 ppm, P. aeruginosa was rarely found except in those pools which used sodium dichloroisocyanurate as a pool disinfectant.


Three private swimming pools using sodium dichloroisocyanurate as a pool disinfectant were found to contain large numbers of the potential pathogen, P. aeruginosa.

Fitzgerald, G. P., DerVartanian, M. E. Factors influencing the effectiveness of swimming pool bactericides, Applied Microbiology, 1967, 15(3), 504-509.

Chlorine demand free buffered water studies. Time required for 99% inactivation (0.25 and 0.1 ppm Cl data estimated from Figure 4)


0.5 0.25 min 4 min 5 min 12 min

0.25 <5 ~10 ~15 ~25

0.1 <5 ~25 ~55 ~70

0.5 + 0.5 ppm NH3 ~180 ~150

Pool studies. Time required for 99.9% inactivation.

0 ppm CYA 25 ppm CYA 100 ppm CYA

Outdoor, 0.5 ppm Cl 2 min

Outdoor, 0.5 ppm Cl, 0.1 ppm NH3 60 min 60 min

Indoor, 0.5 ppm Cl, 0.3 ppm NH3 150 min 120 min 90 min

See Gardiner for discussion of NH3 results.

Fitzgerald, G. P., DerVartanian, M. E. Pseudomonas aeruginosa for the evaluation of swimming pool chlorination and algicides, Applied Microbiology, 1969, 17(3), 415-421.

There is a graph (Figure 1) showing increasing kill times with increasing CYA concentrations. ‘The effect of cyanuric acid was greater as the concentration of chlorine in a test water decreased’. Tests were run with 0.1, 0.25 and 0.5 ppm Cl, 0, 25, 50 and 100 ppm CYA.

FMC Report 5840-R, prepared by Hazelton Laboratories, The effect of cyanuric acid on the bactericidal activity of a swimming pool sanitizer, New York, 1971 (as referenced in Williams). Fuchs, R. J. Lichtman, I. A. FMC, Stabilization of active chlorine containing solutions, US Patent 2,988,471, June 13, 1961.

This invention relates to the stabilization of aqueous solutions containing active chlorine, and particularly to the stabilization of such solutions during exposure to sunlight or in contact with metals, by the addition of a chemical of the class consisting of cyanuric acid, ammelide and their salts.

Gaglierd, A. M. Swimming Pool Weekly (1971) and Swimming Pool Age (1973) Data and Reference Annual Edition, pp. 52-55, (Allegheny County Health Department Study) as referenced in Lachocki). Gardiner, J., Chloroisocyanurates in the treatment of swimming pool water, Water Research, 1973, 7, 823-833.

Spectrophotometric experiments were used to calculate the concentration of hypochlorous acid under various conditions in CYA pools. Published results (Anderson, Fitzgerald, Swatek, etc.) concerning the bactericidal efficiency of the system have been examined in relation to its chemistry. See pg 832 for discussion of the ammonia issue.

Gilcreas, F. W., Morgan, G. B., Chlorinated cyanurates and the effect of cyanuric acid, Swim Pool Age, December 1963, 37, 30-38. Golaszewski, G., and Seux, R. 1994. The kinetics of the action of chloroisocyanurates on three bacteria: Pseudomonas aeruginosa, Streptococcus faecalis, and Staphylococcus aureus. Water Research 28(1), 207-217.


Log reduction in phosphate buffered water (pH 7.5, 25 C)

Organism CYA, ppm Cl2 dose, ppm

15 sec 1 min 2 min 3 min 5 min 10 min

P. aeruginosa a 25 0.7 0.2 0.4 2.3 4.1 5.4 7.9

1.5 0.2 2.8 4.6 5.2 5.9 *

2.3 0.2 3.9 4.7 5.4 5.6 7.3

360 0.8 0 0.1 0.2 0.3 2.5 6.7

1.4 0 0 0.7 2.2 4.2 *

2.1 0.1 0.1 0.8 3.5 5.2 7.0

P. aeruginosa b 25 1.0 0.1 0.8 4.3 5.4 *

1.6 0 4.6 5.7 * *

1.8 0 5.1 6.1 * *

360 1.0 0 0 0.3 1.7 5.4

1.6 0 0 0.5 5.0 *

S. aureus 25 1.0 0.1 1.4 3.3

1.5 0.2 0.4 2.7 4.9 *

2.5 0.1 1.6 4.1 5.7 *

360 1.0 0 0 0.8 2.1 5.0

1.5 0 0.1 0.9 4.9 6.8

2.4 0 0.2 2.9 5.8 7.1

S. faecalis 25 1.0 0 0.6 4.0 5.2 5.7

2.2 0.1 3.6 4.5 5.5

2.5 0.1 3.7 4.7 5.1 5.6

360 0.9 0 0 0 0.2 4.1

1.4 0 0 0 0.4 4.4

1.9 0 0 0.1 1.1 4.3

A Environmental strain B Collection strain * Inactivated

Golaszewski, G., Clement, M., Seux, R., Influence of isocyanuric acid on the reactivity of chlorine with creatinine in swimming pool water, Journal Francais d’Hydrologie, 1988, 19, Fasc. 2, 179-190.

The presence of isocyanuric acid does not perceptibly change the initial kinetics of the chlorination reaction; it involves, in contrast, a great stability of total chlorine over the course of time and is detrimental to hydrolysis reactions. These latter are manifested especially in basic medium by a ring opening which leads to the formation of chlorocreatines. An excess of free chlorine brings about their rapid decomposition into nitrogen trichloride. In the presence of isocyanuric acid, regeneration of creatinine is favored.

Grohman, A., Carlson, S., Bewertung der aufbereitung und desinfektion von schwimmbadwasser bei verwendung von dichlorisocyanurat, Arch. Badewes. 1977, 197-200 (as referenced in VanKlingeren). Hilton, T. B., The chlorinated cyanurates, Swim Pool Age, November 1961, 35, 46-52. Kowalski, X., Hilton, T. B., Comparison of chlorinated cyanurates with other chlorine disinfectants, Public Health Reports, 1966, 81(3), 282-288.

1960 Tests on 15 pools in the St. Louis area. The article does not state whether the chlorine was neutralized before transporting the samples to the laboratory for the bacteriological tests.

Chemical #of pools/ type*

#of tests

Cl, ppm

pH Bather load/ 10,000 gal

CYA, ppm

%Disinfection failures

Plate count >200

E. coli >0

Cl gas + CYA 1 PO 15 0.7 7.3 2.0 25 13 0

Cl gas 3 PO 37 0.6 7.7 0.9 0 5 2

KDCCA + CYA 1 SO 17 0.4 7.2 0.7 31 6 0

Cl gas, NaOCl, 4 SO 54 0.6 7.6 1.1 0 15 2


Ca(OCl)2

Cl gas + CYA 1 PI 22 0.6 7.2 2.2 33 24 0

Cl gas 1 PI 9 0.9 7.1 2.2 0 66 22

KDCCA + CYA 4 RO 28 0.4 7.4 0.2 40 11 4

* PO = Public outdoor, SO = Semipublic outdoor, PI = Public indoor, RO = Private outdoor 1963 Inspection records for 138 pools in the St. Louis area. Only 7 of the pools were treated with chlorinated cyanurates, and all of these were KDCCA pools. Information on the cyanuric acid levels in the pools with chlorinated cyanurates was not available. The authors do not report any CYA levels for any of the 138 pools. The percent disinfection failures for the KDCCA pools were not statistically different from the ‘Other’ pools.

Chemical #of pools/ type*

#of tests

Cl, ppm

pH Bather load/ 10,000 gal

%Disinfection failures

Plate count >200

E. coli >0

KDCCA 2 PO 15 0.6 7.5 17 0 0

Other 58 PO 463 0.4 7.6 26 6 19 819

KDCCA 5 SO 42 0.7 7.4 5 311 65

Other 19 SO 204 0.5 7.7 4 1439 1138

Lachocki, T. M., The impact of cyanuric acid on pool and spa water, Presentation slides from NSPI International Expo & Conference, Chicago, IL, November 13, 1997.

Cites data from Andersen, Ditzel, Gilcreas & Morgan, Fitzgerald and DerVartanian, Swatek et al.,

LeGuyader, M., Grateloup, I., Relative importance of different bacteriological parameters in swimming pool water treated by hypochlorite or chloroisocyanurates, Journal Francais d’Hydrologie, 1988, 19, Fasc 2, 241-250.

Survey of 3750 pools treated with either chloroisocyanurates or hypochlorite. CYA levels are not given. Results expressed in percentage of the number of pools whose water showed, at the time of bacteriological analysis, the presence of the specified bacteria.

Hypochlorite Chloroisocyanurate

Staphylococci 50.31 60.03

Pseudomonas 2.93 14.31

Coliforms 0.33 1.42

Lin, S., Rouse, D., All Fouled Up, Aquatics International, April 2004, 16(4), 16.

Decrease in ORP with fouling of probe. Cleaning of probe gave improved ORP reading, but still less than 0 ppm CYA value.

Linda, F. W., Hollenbach, R. C., The bactericidal efficiency of cyanurates- a review, Journal of Environmental Health, 1978, 40(6), 324-329. Manning, M. J., Studies concerning the chemical aspects of an ORP controller, Internal Report, Olin Corporation CNHC-RR-90130, May 15, 1990. Matzner, E. A., Bactericidal effectiveness of chlorinated cyanurates, Research Report of Monsanto Chemical Company, St. Louis, MO, June 1961. Monsanto, A review for the environmental protection agency on the commercial and technical benefits of the chlorinated-s-triazinetrione products, prepared by Industry Ad Hoc Committee Chlorinated Cyanurates, May 9, 1980.

No new data is provided here, but it does discuss a lot of data that is not readily available, such as the following algae data from G. D. Nelson, F. B. Clarke, and R. Kimerle, “Problems in Pool Water Management,” Paper read at Lab Vegas, NSPI Convention, January, 1973.


Growth of ~100 cells/ml algae in simulated pool water, 275 ppm hardness. Standard AAP nutrients present in 125 ml flasks exposed to fluorescent light, in quadruplicate. Conditions for zero growth, ppm Cl2

Algae Species 0 ppm CYA 75 ppm CYA 125 ppm CYA 200 ppm CYA 300 ppm CYA

Oscillatoria 0.5 0.5 -- -- 0.5

Selenastrum Capricornutum 1.0 1.0 1.0 1.0 1.0

Characium Polymorphum >2.5 >2.5 >2.5 >2.5 >2.5

They also quote a study performed by the Water Research Centre (Ref 33 = Letter from Committee of New Chemicals and Materials of Construction for use in Public Water Supply and Swimming Pools, Department of the Environment, London)

On the basis of laboratory tests, the reduction in the level of kill with increasing concentrations of cyanuric acid is very marked. However, this effect is not directly proportional to the concentration of cyanuric acid present over a range from 1 to 800 mg/l.

According to the Monsanto report ‘after a complete review of existing data, the Committee of New Chemicals and Materials of Construction for use in Public Water Supply and Swimming Pools gave approval for the use of s-triazinetrione and its chlorinated derivatives at a level of 400 ppm (reference 33).’ Monsanto does provide a graphs of Chlorination of Ammonia to Breakpoint with 0 ppm and 500 ppm with 1 hour reaction times, and 0 ppm and 200 ppm CYA with 5 minute reaction times. The amount of chlorine to reach breakpoint is ~the same between 0 ppm and 500 ppm with a 1 hour reaction time and between 0 ppm and 200 ppm CYA with a 5 minute reaction time. They do not report 500 ppm CYA data with a 5 minute reaction time.

Morgan, G. B., Gilcreas, F. W., Gubbins, P. P., Cyanuric acid- an evaluation, Swimming Pool Age, May 1966, 40(5), 31-38. I am not sure I have the complete article.

This article has a lot of data in tables and graphs, but the source of the data is unknown. Some of the data (Tables 6 and 7, Figures 1 and 2) are not even discussed in the text. Following is the data that was discussed in the text. ‘Early work’ using Escherichia coli and Micrococcus pyrogenes in the A.O.A.C. procedure. Time (minutes) to achieve a ‘-‘ reading using CDB-60 (NaDCCA)

Av. Cl, ppm 0 ppm CYA 25 ppm CYA 50 ppm CYA 100 ppm CYA

E. coli

0.3 >35 >35 >35 >35

0.5 25 25 25 25

0.6 25 25 20 25

1.0 15 15 15 15

M. pyrogenes

0.35 >35 >35 >35 >35

0.5 25 25 25 25

0.6 25 25 30 25

1.0 20 20 20 15

‘Later work’ which utilized the testing procedure of Stuart and Ortenzio. Time (minutes) to achieve <3 MPN/100 ml (MPN = most probable number) using NaOCl

Av. Cl, ppm 70 F

0 ppm CYA

25 ppm CYA

50 ppm CYA

75 ppm CYA

100 ppm CYA

150 ppm CYA

200 ppm CYA

E. coli

0.2 0.5

0.7 0.5

0.85 0.5

1.1-1.4 0.5 0.5 0.5 1, 0.5 1, 1, 2-10

Strep. Faecalis

0.75 0.5

0.85-0.90 1 1 2-10

1.1 0.5 0.5 >10

1.2 0.5 1 1 2-10

1.4 0.5 0.5, 1 0.5, 1

1.5 1

1.6 0.5 1

1.7 0.5 1 1

1.9 0.5


Nelson, G. D., Swimming pool disinfection with chlorinated isocyanurates, Special Report 6862, Monsanto Chemical Company, St. Louis, MO, 1967.

Disinfection studies in pool water were conducted at California State College at Long Beach during the summer of 1966 by F. E. Swatek, H. Raj, and G.E. Kalbus. I think this is the same data as discussed in Swatek et al. (see below). Time, minutes for 99.9% kill. Ranges for kill time given below are the 95% confidence limits for the averaged data from 6 pools.

Cl, ppm 0 ppm CYA 25 ppm CYA 50 ppm CYA 100 ppm CYA 200 ppm CYA

E. coli

0.5 0.9-15 1.2-19 1.5-24 2.2-36 2.5-40

1.0 0.4-6.0 0.5-8.0 0.5-9.0 0.7-12 1.4-15

1.5 <0.3-4.0 0.3-4.51 0.3-5.0 0.4-7.0 0.4-7.5

2.0 <0.3-4.0 <0.3-4.0 <0.3-4.0 0.3-4.5 0.3-5.0

S. Faecalis

0.5 1.1-11 1.3-13 1.3-13 1.2-15 2.5-25

1.0 0.6-6.0 0.7-7.0 0.7-7.0 0.8-7.6 1.1-11

1.5 0.5-4.5 0.5-4.5 0.5-4.5 0.5-4.8 0.5-5.5

2.0 0.3-3.2 0.3-3.2 0.3-3.2 0.3-3.2 0.3-3.4

S. aureus

0.5 0.6-32 0.8-40 0.9-49 1.3-68 >1.5-75

1.0 0.4-22 0.5-27 0.7-31 0.8-44 0.8-64

1.5 0.3-14 0.3-15 0.4-20 0.5-26 0.8-40

2.0 0.2-7.5 0.2-9 0.2-11 0.3-15 0.5-24

Ps. Aerug.

0.5 1.4-21 1.6-26 2.2-34 2.5-38 2.5-38

1.0 0.7-11 1.0-14 1.3-19 1.6-23 1.6-23

1.5 0.5-7.0 0.7-10 1.0-13 1.6-16 1.2-16

2.0 0.3-4.7 0.5-7.4 0.7-10 0.9-12 0.9-12

Based on the statistical analysis, Nelson concludes pg V-53: ‘Cyanuric acid at levels up to 200 ppm has no significant effects on kill time for the four organisms studied. The three effects for cyanuric acid reported by the workers at Long Beach (delay, no effect and acceleration of kill) become no effect when the precision of the biocidal measurements is considered.’

Nowell, LH, Hoigne J, Photolysis of aqueous chlorine at sunlight and ultraviolet wavelengths I. Degradation rates,’ Water Res. 1992, 26, 593-598. As referenced in Carlsson 1994. O’Brien, J. E. Morris, J. C., Butler, J. N., Equilibria in aqueous solutions of chlorinated isocyanurates, In: Chemical Water Supply Treatment, Chapter 14, pp. 333-358; edited by A. J. Rubin, Ann Arbor Sciences, Ann Arbor, MI 1974. Presented at the District Symposium, Philadelphia, 1973.

This article does not give any new efficacy data, but discusses the amount of free chlorine that will be present in isocyanurate solutions. According to Figure 9, if the total Cl concentration is 1.4 ppm and CYA = 25 ppm, the free chlorine concentration (i.e. the chlorine not bound by CYA) will be ~0.05 ppm at pH 7.

O’Brien, J. E., Hydrolytic and ionization equilibria of chlorinated isocyanurate in water, Ph.D. Dissertation, Cambridge, MA: Harvard University, 1972. Ortenzio, L. F., Stuart, L. S., The behavior of chlorine bearing organic compounds in the AOAC available chlorine germicidal equivalent concentration test, J. Assoc. Official Agric. Chem., 1959, 42, 630-633. Peck, L. E., Swimming pool water quality study, Pinellas County Health Department, St. Petersburg, FL, from pool data for 1975.

There is some raw data in the report. Following is a summary % Bacteriologically unsatisfactory cyanuric acid pools = 8% % Bacteriologically unsatisfactory pools without cyanuric acid = 11% % Cyanuric acid pools below 100 ppm bacteriologically satisfactory = 91% % Cyanuric acid pools above 100 ppm bacteriologically satisfactory = 93% % Cyanuric acid pools with no chlorine residual = 8% % Pools with no cyanuric acid and no chlorine residual = 14%


See Rakestraw for another ref to Pinellas County study in 1992.

Petrie, E. M., Roman, D. P., Chlorine sanitizing compounds, Soap Chem. Specialties, 1958, 34, 67-68. Petritsi, I., The influence of cyanuric acid on the bactericidal and viricidal effectiveness of chlorine, An essay presented to the faculty of the Department of Epidemiology and Public Health, Yale University, in candidacy for the degree of Master of Public Health, 1964.

Phosphate buffered distilled water. Average time required to achieve 6 log reduction (for 2 out of 3 with Cl concentrations of 0.45-0.56 and pH 6.9-7.1)

Organism 0 ppm CYA 2.5 ppm CYA 25 ppm CYA

E. coli 30 seconds 2 minutes 3 minutes

S. faecalis 30 seconds 3 minutes 3 minutes

S. aureus 1 minute 2 minutes

Poliovirus type 1 (4 log, pH 7.5) 120 minutes 180 minutes

Pfaffenberger, D. C., Briggle, T. V. Swimmer clearance of cyanuric acid, Paper presented at Sixth Annual Meeting of the Society of Environmental toxicology and Chemistry, St. Louis, MO, 1985. Pinsky, M. L., Hu, H. C., Evaluation of the chloroisocyanurate hydrolysis constants, Environmental Science and Technology, 1982, 4, 423-430. (or 1981, 15, 423-30?) Pinsky, M. L., Hu, H. C., Evaluation of the chloroisocyanurate hydrolysis constants, Environmental Science and Technology, 1981, 15(4), 423-430.

Table 1 Summary of Equilibrium Constants and Experimental Methods

Ref K1 K2 Experimental Method Ionic Strength, M

Temp, C

4 31.6 9.6 PH titration, spectrophotometry 0.5 23

3 44.2 3.2 Spectrophotometry 0.3 23

5 98.0 7.7 Ph titration, spectrophotometry 0.02 25

1 235 34 Linear sweep voltammetry at carbon electrode

0.1 22 +/-

6.0 0.2 15.5

28 0.2 25.0

60 0.2 30.0

K1 Cl2CA- + OH- HClCA- + OCl- K2 HClCA- + OH- H2CA- + OCl- 1 This work (Pinsky, 1981) 3 Gardiner, J. Water Res. 1973, 7, 823-33 4 Brady, A. P.; Sancier, K. M.; Sirine, G. J. Am. Chem. Soc. 1963, 85, 3101-4. 5 O’Brien, J. E. Ph.D. Thesis, Harvard University, Cambridge, MA, 1972.

Rakestraw, L. F., Downes, J. E., Healy, C. E., Efficacy and safety of the use of chlorinated isocyanurates in swimming pools and spas, Monsanto Final Report number MSL-9946, February 14, 1990.

Cites data from Pinellas County Health Department study (Peck). Concludes that ‘pools containing 1-3 ppm of total chlorine and up to 800 ppm of cyanuric acid were found to be sanitized satisfactorily.’


Rakestraw, et al. (1994) NSPI Int. Expo. New Orleans [Oxy/Pinellas] as referenced by Lachocki, study of 486 commercial pools July-Nov. 1992. Robinton, E.D., and Mood, E.W., An evaluation of the inhibitory influence of cyanuric acid upon swimming pool disinfection. American Journal of Public Health, 1967, 57(2) :301-310.

Concentration of FAC (ppm) needed to obtain 99.999% inactivation Distilled water, 25 C, pH 7.2, alkalinity 50 ppm.

Source of Cl

Organism Time of exposure CYA, ppm Ca(OCl)2 TCCA KDCC

E. coli 30 sec 0.0 <0.11 <0.11 <0.11

E. coli 30 sec 50.0 0.97 0.80 >0.80

Strep. Faecalis 2 min 0.0 <0.10 <0.11 0.11

Strep. Faecalis 2 min 50.0 0.51 0.42 0.43

Staph. aureus 5 min 0.0 <0.40 <0.61 0.64

Staph. aureus 5 min 50.0 1.64 >0.90 >1.62

Roth, Swim. Pool Weekly & Swim. Pool Age Data & Ref. Ann. Ed. As referenced by Lachocki. Roth, E. S. ,’How the Cyanurates act as a stabilizer, sanitizing instrument in swimming pools,’ Swimming pool weekly and Swimming pool age, 43, 37-40, 1969. As referenced by Faust and Gower in Water (Swimming Pools) vol 22 of The Kirk-Othmer Encyclopedia of Chemical Technology, 3

rd edition, John Wiley and Sons, 1979.

Scotte, P., Swimming pool water disinfection conditions with chloroisocyanurates, Journal Francais d’Hydrologie, 1988, 19, Fasc. 2, 169-178.

No activity data. I think the chemical equilibria data are from O’Brien. Scotte is arguing that the CYA limit for France should be raised from 75 ppm.

Scotte, P., The cyanuric acid cycle in swimming-pool water treatment, ???, TRCNH 89-2735.

No activity data. The paper gives equations for estimating the build-up of CYA based on chemical dosage and water replenishment rates. Scotte is arguing that the CYA limit for France should be raised from 75 ppm.

Scotte, P.; Billaud, G. Hydrolysis of Chloroisocyanurates, Practical Consequences, Sciences De L’Eau, 1987, 6, 145-167 (in French).

The only biocidal activity data is cited from Gardiner. Lots of calculations of chlorine species with varying pH, CYA, and Cl, based on constants from Pinsky and O’Brian. A graph of Cl, Br, CYA species adsorptions at various wavelengths. Does not give experimental or cite reference for this data.

Seux, R., Batto, M., Clement, M., Beauducel, B., The evolution of chloroisocyanurates in aqueous solution and the behavior of the chlorinated forms with diethylparaphenylenediamine (DPD), T.S.M.-L’EAU, December 1984, 79(12), 617-625.

No activity data.

Sommerfeld, M. R., Adamson, R. P., Influence of stabilizer concentration on effectiveness of chlorine as an algicide, Applied and Environmental Microbiology, Feb 1982, 43(2), 497-499.

Chlorine demand-free culture medium with stabilizer, chlorine dose and algal inoculum. Algae were isolated from swimming pools from the Phoenix metropolitan area and maintained in unialgal culture. CYA concentrations used were 0, 25, 50, 100 and 200 ppm. Exposure time was 24 hours. There were only very slight differences between the 0 ppm and 25 ppm values. No significant changes in activity were seen above 25 ppm. In the following table, the viable colonies of algae were estimated from the figures.

Algae 1.0 ppm Cl 1.5 ppm Cl 2.0 ppm Cl

0 ppm CYA 25 ppm CYA 0 ppm CYA 25 ppm CYA 0 ppm CYA 25 ppm CYA

P. pyrenoidosa 4300 4800 1600 2800 800 1000


Oocystis sp. 4200 4700 3200 3600 0 0

P. minnesotense 2300 2700 0 0 0 0

Steininger, J. M., In Control- Automation helps low levels of chlorine do the job, Swimming Pool/Spa Age, 1989, 63(11), 62-64.

Figure 1 has a graph of the effect CYA has on the ORP reading. For 2 ppm Cl, the ORP was ~830 mV. With 40 ppm CYA, the same level of Cl gave and ORP of ~700.

Stuart, L. S., Ortenzio, L. F., Swimming pool chlorine stabilizers, Soap Chem. Specialties, 1964, 40(8) 79-82, (112-113?). Swatek, F. E., Raj, H., Kalbus, G. E., A laboratory evaluation of the effect of cyanuric acid on the bactericidal activity of chlorine in distilled water and seven swimming pool water systems, Paper presented at National Swimming Pool Institute Convention, January 21, 1967, Las Vegas, Nevada.

No data tables are presented. For the distilled water studies, an increase in kill time was seen with an increase in CYA concentration. For the pool studies, contradictory results were seen. In some cases, kill times increased with CYA concentration, others, the kill time decreased with CYA. “It must be concluded that the effect of cyanuric acid on the efficiency of chlorine disinfection is significantly different from water system to water system. Any attempt to summarize bacteriological data obtained from tests made in widely diverse environments is extremely difficult and could easily lead to incorrect conclusions if over-simplified.” Statistical calculations were performed on Swatek’s pool data by Nelson (vide supra).

Tachikawa, M., Saita, K., Sawamura, R., Inactivation of poliovirus with chlorine compounds and effects of chloramine formation, Jpn. J. Toxicol. Environ. Health, 1995, 41(1), P6 (Abstract in English).

In PBS virus suspension, 99% of virus was inactivated with 0.4 ppm of NaOCl within a minute, but with the NaOCl solution containing 30 ppm isocyanuric acid, virus inactivation required longer than 5 minutes.

Umeda, T., Funabashi, M., Nakamura, A. Inoue, H., Effect of isocyanuric acid on the bactericidal effectiveness of chlorine, 1982, Chem. Abstr. 97:2145c?? Hard to read ref in Carlsson 1994. VanKlingeren, B., Pullen, W. Reijnders, H. F. R., Quantitative suspension test for the evaluation of disinfectants for swimming pool water: Experiences with sodium hypochlorite and sodium dichloroisocyanurate, Zbl., Bakt. Hyg., I. Abt. Orig. 1980, B 170, 457-468.

Buffered bovine albumin solution studies, log reduction values using NaOCl

Free chlorine, ppm

0.3 0.3 0.3 0.3 0.5 0.5 0.5 0.5 1 1 1 1

Time, min 0.5 1 2 5 0.5 1 2 5 0.5 1 2 5

Test strain

Staph. aureus

3.9 4.0 >5 >5 4.3 >5 >5 >5 4.8 >5 >5 >5

Str. faecalis >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 P. aeruginosa

2.5 3.2 3.6 3.6 3.7 3.5 4.1 4.4 >5 >5 >5 >5

Prot. mirabilis 4.0 4.5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 E. coli >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 >5 C. albicans <0.2 <0.2 <0.2 0.2 <0.2 <0.2 1.0 3.3 0.6 3.3 >4 >4

Buffered bovine albumin solution studies, log reduction values using NaDCC (no additional CYA)

Free chlorine, ppm

2 2 2 2 4 4 4 4 8 8 8 8

Time, min 0.5 1 2 5 0.5 1 2 5 0.5 1 2 5

Test strain

Staph. <0.2 <0.2 <0.2 <0.2 0.2 3.1 3.5 3.6 >5 >5 >5 >5


aureus

Str. faecalis <0.2 <0.2 <0.2 <0.2 <0.2 1.2 4.3 4.4 >5 >5 >5 >5

P. aeruginosa

<0.2 <0.2 0.2 0.2 2.1 2.1 2.7 3.1 3.1 4.9 4.2 >5

Prot. mirabilis <0.2 <0.2 <0.2 <0.2 2.3 3.7 4.8 >5 >5 >5 >5 >5

E. coli

C. albicans <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 2.3

Buffered bovine albumin solution studies, log reduction values using NaDCC + 100 ppm CYA

Free chlorine, ppm

2 2 2 2 4 4 4 4 8 8 8 8

Time, min 0.5 1 2 5 0.5 1 2 5 0.5 1 2 5

Test strain

Staph. aureus

<0.2 <0.2 <0.2 <0.2 <0.2 <0.2 0.4 4.0 0.7 4.2 >5 >5

Str. faecalis <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 1.3 4.0 1.0 >5 >5 >5

P. aeruginosa

<0.2 <0.2 0.2 0.3 0.3 1.0 2.3 2.6 1.5 2.3 >5 >5

Prot. mirabilis <0.2 <0.2 <0.2 <0.2 2.7 2.9 >5 >5 >5 >5 >5 >5

E. coli

C. albicans <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 0.2

Victorin, K., Hellstrom, K. G., Rylander, R., Redox potential measurements for determining the disinfecting power of chlorinated water, J. Hyg., Camb., 1972, 70, 313-323.

The following conclusion was made in the text: ‘During the 3 min. period cyanuric acid reduces the effect of NH2Cl and forms a combined residual with hypochlorite with lower disinfective power than pure hypochlorite.’ In the experiments with hypochlorite, the concentration of free available chlorine was too low to be measured. This value was then calculated, starting from a stock solution of hypochlorite. In all other experiments, the measured total available chlorine was recorded. In all of these, no free available chlorine could be detected. Table 1

Chlorine compound Survival of E. coli (%) AvCl, mg Cl2/l Redox potential, mV

NaOCl 100 0 312

60 0.008 307

9 0,02 345

0.9 0.03 330

0.05 0.04 356

0.003 0.05 465

0 >0.06 >490

CYA + NaOCl 100 0 310

54 0.07 333

4.0 0.15 364

0.1 0.15 380

0.01 0.13 425

0.005 0.20 449

0 >0.34 >540

NH2Cl 100 0 311

37 0.39 393

0.9 0.53 370

0 >0.53 >450

CYA + NH2Cl 100 0 311

28 0.48 403

0.001 0.69 414

0 >0.69 >465


Warren, I. C., Ridgway, J. Swimming pool disinfection. Investigations on behalf of the Department of the Environment into the practice of disinfection of swimming pools during 1972 to 1975. Tech. Rep. TR 90 – Water Res. Cent., 1978, Medmenham, England. Water Research Center, Swimming pool disinfection, Technical Report TR 90, Steverage, Herts, G. G., 1975, 1-35 (as referenced in ScotteTRCNH 90-2804). Weidenbach, Kelly N. Swimming pool water quality: An analysis of outdoor public swimming pools in Pinellas County, Florida, A report submitted to the Department of Epidemiology, Rollins School of Public Health, Emory University, in partial fulfillment of the requirements for the degree of Master of Public Health, December 2004. Williams, K., Cyanurics- Benefactor or bomb?, The PPOA Pumproom Press, Summer 1995, 7, 3-5.

Plain language review (copy of two part series from Williams has list of references).

World Health Organization, Guidelines for Safe Recreational Water Environments, Volume 2, Swimming Pools and Similar Environments, 2006, ISBN 92-4-154680-8, page xvii, http://www.who.int/water_sanitation_health/bathing/bathing2/en/

‘Where chlorinated isocyanurates are used, levels of cyanuric acid in pool water should not exceed 100 mg/l.’

Wojtowicz, J. A., Relative bactericidal effectiveness of hypochlorous acid and chloroisocyanurates, Journal of the Swimming Pool and Spa Industry, 1996, 2(1), 34-41.

Analysis of data from O’Brien, Anderson, and others.

Yamashita, T., Sakae, K., Ishihara, Y., Inoue, H., and Isomura, S. 1985. Influence of cyanuric acid on viricidal effect of chlorine and the comparative study in actual swimming pool waters. Kansenshogaku Zasshi, March 3, 1988, 62(3), 200-205.

99.9% Inactivation time in buffer studies, 0.5 ppm FAC, 25 C

Organism No CYA, min 30 ppm CYA, min

Poliovirus 1 0.8 5.6

Coxsackievirus A24 0.5 14.4

Enterovirus 70 0.12 2.5

Adenovirus type 3 0.14 2.1

99.9% Inactivation time in pool water studies, 1.0 ppm FAC, 25 C

Organism No CYA, min 30 ppm CYA, min

Poliovirus 1 0.4 4.4

Yamashita, T., Sakae, K., Ishihara, Y., Isomura, S., The influence of cyanuric acid on the virucidal effect of combined available chlorine, Nippon Koshu Eisei Zasshi, 1989, 36(6), 353-6 (Abstract in English).

Poliovirus type 1 studies in chlorine demand free buffer, pH 7.0, 25 C. Time for 99.9% inactivation (minutes) with 1 ppm available chlorine.

CYA, ppm 0 M NH3 10 M NH3 100 M NH3

0 0.5 14 187

25 2.4 11 105

50 2.9 11 76

100 4.2 12 51

Poliovirus type 1 studies in chlorine demand free buffer, pH 7.0, 25 C. Time for 99.9% inactivation (minutes) with 10 ppm available chlorine.

CYA, ppm Free Available Chlorine, ppm

Time, minutes with

100 M NH3

http://www.who.int/water_sanitation_health/bathing/bathing2/en/


0 <0.1 12.0

25 0.3 4.8

50 0.3 4.3

100 0.3 3.4

Yamashita, T., Sakae, K., Ishihara, Y., Isomura, S., Inoue, H., Viricidal effect of chlorinated water containing cyanuric acid, Epidem. Inf., 1988, 101:631-639. Hard to read ref in Carlsson 1994. Yamashita, Teruo; Sakae, Kenji; Ishihara, Yuichi; and Isomura, Shin, Microbiological and Chemical Analyses of Indoor Swimming Pools and Virucidal Effect of Chlorine in These Waters, 1990, Jap. J. Publ. Health, 37, 962-966. Abstract in English, article in Japanese.

Samples from 6 public indoor swimming pools. ‘Total plate counts ranged from 0 to 1 per ml in the swimming pools treated with sodium hypochlorite and 0 to 51 in those with trichloroisocyanurates….In 11 of 12 water samples of swimming pools using sodium hypochlorite, poliovirus 1 was inactivated within 1 min under the condition of 1.0 mg/l free available chlorine and 25º C. In 11 of 12 water samples of 3 swimming pools using trichloroisocyanurates, poliovirus type 1 survived after 2 min contact while in 5 samples poliovirus type 1 survived after 5 min contact. This shows that the risk of viral infection is greater in swimming pool water treated with chlorinated isocyanurics than that with sodium hypochlorite.’

Documents

Effect of Cyanuric Acid on Disinfection - Another … of... · disinfection, Official Report of the Nassau County Department of Health, 1971, Mineola, NY. Favero, M. S., ... There