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Chemical Intervention in Swimming Pools: A Proposed Definition for Shock Treatment. Paul Chrostowski and Sarah Foster CPF Associates, Inc. NEHA 66 th Annual Educational Conference. This Presentation Will Discuss. Recreational waterborne disease Emerging infectious disease

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

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Chemical intervention in swimming pools a proposed definition for shock treatment l.jpg

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

Paul Chrostowski and Sarah Foster

CPF Associates, Inc.

NEHA 66th Annual Educational Conference


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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


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Waterborne Disease Trends

Source: MMWR (May 2000).


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Emerging Infectious Diseases

  • Once under control, now on rise

  • Human mobility (Ebola)

  • Food imports (Salmonella on strawberries)

  • Immunocompromised individuals

  • Sequelae more important than thought


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Sources of Microorganisms to Pools

  • Accidental fecal release (also other body fluids)

  • Inadvertent shedding

  • Exogenous sources (dirt, leaves, other vectors)

  • Pool fill water


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Potable Water Disease Outbreaks


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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


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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


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Anatomy of a Pool Problem - Agents

  • Ps aeruginosa

  • Cryptosporidium

  • Legionella

  • E Coli O157

  • Enterovirus

  • Mycobacterium

  • Giardia


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Anatomy of a Pool Problem -- Disinfectants

  • Chlorine

  • Ozone

  • Chlorine/bromine

  • Hydrogen peroxide

  • In all cases, disinfectant residual was inadequate or incorrectly measured


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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


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Pool Water  Drinking Water


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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


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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


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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


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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.


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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


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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


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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


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Issues Associated with Shock


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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


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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


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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


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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


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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.


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