Chemical Intervention in Swimming Pools: A Proposed Definition for Shock Treatment

1. Chemical Intervention in Swimming Pools: A Proposed Definition for Shock Treatment Paul Chrostowski and Sarah Foster CPF Associates, Inc. NEHA 66th Annual Educational Conference

2. This Presentation Will Discuss • Recreational waterborne disease • Emerging infectious disease • Sources of microorganisms to pools • Pool disinfectants • Diagnosis of pool and spa problems • Shock treatment • Treatment protocols • Additional issues

3. Waterborne Disease Trends Source: MMWR (May 2000).

4. Emerging Infectious Diseases • Once under control, now on rise • Human mobility (Ebola) • Food imports (Salmonella on strawberries) • Immunocompromised individuals • Sequelae more important than thought

5. Sources of Microorganisms to Pools • Accidental fecal release (also other body fluids) • Inadvertent shedding • Exogenous sources (dirt, leaves, other vectors) • Pool fill water

6. Potable Water Disease Outbreaks

7. Frequently Used Less Frequently Used Infrequently Used Chlorine Products Bromine Products Bromine-chlorine Ozone (plus halogen) UV (with or without ozone) Chlorine dioxide Iodine Peroxides Silver/Copper Biguanide Potassium permanganate Electrolytic generation Pool Disinfectants

8. Anatomy of a Pool Problem - Outbreaks • 15 outbreaks adequately reported • 12 routine outbreaks/3 incidents • 7 gastroenteritis • 5 dermatitis/folliculitis • 2 pulmonary • 1 mixed endpoint

9. Anatomy of a Pool Problem - Agents • Ps aeruginosa • Cryptosporidium • Legionella • E Coli O157 • Enterovirus • Mycobacterium • Giardia

10. Anatomy of a Pool Problem -- Disinfectants • Chlorine • Ozone • Chlorine/bromine • Hydrogen peroxide • In all cases, disinfectant residual was inadequate or incorrectly measured

11. Survey of 15 Residential Spas • Used dichlor, cal hypo, electrolytic, or BCDMH • pH average: 7.5 (5.37-8.23) • Free Ox residual average: 13.04 ppm (0-59 ppm) • Total plate count average: 108 cfu/mL (0-TNTC) • 4/15 plates: TNTC or overgrown, free Ox residual 0-0.2 ppm

12. Pool Water  Drinking Water

13. Proposed Solution is Chemical Intervention • Shock treatment has potential to reduce incidence of waterborne-deisease • Shock treatment, superchlorination, breakpoint chlorination usage is haphazard and often ineffective • Manufacturers promote shock for aesthetics and organoleptic control, not disinfection • Definition of shock and protocol for usage is needed

14. Shock Treatment Proposed Definition • Shock is the addition of an immediately available, oxidizing disinfectant routinely or as intervention • Shock chemical must be effective against bacteria, viruses, fungi, protozoa, and algae with reasonable CT • Shock chemical must destroy organics and nitrogen compounds with reasonable reaction time

15. Shock Treatment Proposed Definition (Continued) • Shock dose must be measurable • Shock results should generally be visible • Routine shock involves raising free chlorine to a minimum of 10 ppm for 1-4 hours weekly for pools and daily for spas • Intervention shock for a water quality problem involves raising free chlorine to 20 ppm for 8 hours

16. Shock Treatment Proposed Definition (Continued) • Intervention shock for public health involves following Maryland-type protocol based on CT. • pH, water balance, and filtration should be maintained during shock treatment. • Bathers can safely re-enter the water when free chlorine is < 10 ppm.

17. Useful Shock Chemicals • Inorganic chlorine compounds such as sodium, lithium, or calcium hypochlorites all fit definition • Dichlor fits definition, if residual cyanuric acid is controlled • Inorganic brominated compounds may fit definition if residual bromate is controlled • Stabilized chlorine dioxide may fit definition, residuals hard to attain

18. Shock Protocols – Maryland DHMH • Maryland DHMH focuses both on prevention and intervention • Maryland DHMH Chemical intervention includes minimum FAC (10 ppm), pH 7.2-7.5, re-entry based on CT data

19. Shock Protocols – New South Wales/Health • NSW/Health includes prevention, education, chemical intervention including weekly shock at 10 ppm FAC overnight • Shock allows pool to catch up on disinfection • More effective against Crypto • Extra oxidation, aids filtration, clarification • Destroys biofilms that may harbor resistant organisms

20. Issues Associated with Shock

21. Resistant Microorganisms • Giardia, Cryptosporidium typically have highest CT values • CT for Crypto ranges from 7200 to 8400; 20 ppm for 6-7 hours • New studies suggest lower CTs might be effective, especially if chloramine is present • Good filtration always important

22. Bather Re-entry Halogen Level • Currently most states and NGOs recommend chlorine residuals up to 4 ppm • Some jurisdictions allow up to 10 ppm, especially in spas and kiddie pools • Toxicological data shows levels up to 10 ppm will have no adverse effect • Bather load and other conditions will rapidly reduce this residual

23. Disinfection Byproducts (DBPs) • Prudent to meet drinking water standards • Organic carbon is most significant determinant of DBPs – algal blooms, high bather load • Other factors including temperature and water age are also important • Type of disinfection not important

24. Shock and DBPs • Study on 114 U.S. residential pools showed no significant difference in THM levels between pools shocked or not shocked • Study on 20 Texas pools showed shocked pools can meet drinking water standards for THMs (averages 30-52 ppb) • Possible reason for low THM levels may be oxidation of organic precursors

25. Conclusions • Recreational waterborne disease is not losing significance as a environmental health problem • Most outbreaks may be prevented or treated by chemical intervention. • Shock treatment using a rigorous definition and with comprehensive protocols is an effective form of chemical intervention.