Pool water treatment

Contaminant of the month: Swimming pool water treatment

February 1, 2016

Contamination risks mainly include pathogenic microorganisms as well as organic and inorganic chemical disinfectant by-products.

What is that?

  • Swimming pools, spas and even therapeutic baths are common sources of exposure to contaminants that can cause illness.
  • Indoor and outdoor swimming pools have somewhat different health risk issues.
  • Contamination risks mainly include pathogenic microorganisms as well as organic and inorganic chemical disinfectant (DBP) by-products.
  • Many disinfectants are used in swimming pools. The forms of chlorine are most common in the United States, but the forms of bromine are also used.

Sources of contamination

  • Human fluids such as perspiration, surface contamination of skin / dirt, urine and feces are the main contaminants of health concern.
  • Outdoor swimming pools can be contaminated with bird droppings, algae, dirt, leaves and runoff.
  • Indoor pools aren’t as exposed, but they have other health issues, especially from inhaling airborne contaminants.

Health problems

  • Human and sometimes environmental microbial contamination is the biggest health problem.
  • Pathogens and illnesses associated with swimming pool water include ear infections, rashes, cryptosporidiosis, giardiasis, bacteria and viruses.
  • Exposures occur by ingesting swimming pool water; contact with the membranes of the nose, mouth and ears; skin contact; and inhalation.
  • The infectious risks arise mainly from ingestion and contact with the membranes.
  • Both organic and inorganic DBPs create potential problems.
  • Skin absorption and inhalation of volatile organic chemicals DBP are major chemical exposures. Others result from the ingestion of water.
  • Inhalation exposure of swimmers occurs at the surface-air interface of water. Inhalation also occurs outside of water in indoor swimming pools if ventilation is not effective. Some studies have found higher blood levels of chloroform after swimming.
  • Inorganic and organic chloramines can be irritating to the skin, eyes and lungs.
  • Instead of chlorine, trichloramine (NCl3), which forms from excess chlorine reacting with ammonia, is probably the eye irritant that many people experience.
  • Reports have suggested potential allergic-type claims to chloramines as well as adverse effects in asthmatics.
  • People with recent gastrointestinal illness / diarrhea, especially children, should not be allowed in swimming pools, and swimmers should shower before entering the pool to remove dirt from the surface.

Read more: Maintaining spa water quality is easier than you think

Water treatment

  • Treatment and maintenance of pool water includes skimming oils and accumulated residues, filtration, recirculation, disinfection and oxidation processes, periodic draining and sanitation, and shock chlorination. .
  • Common disinfection methods include chlorination (chlorine gas, hypochlorite, chlorinated isocyanurates) and bromination (eg bromochlorodimethylhydantoin). Copper ion has some applications, especially in outdoor swimming pools. Chlorine is not effective against Cryptosporidium contamination.
  • Chlorine gas costs less, but also carries the risk of handling and rejection.
  • The general relative disinfection powers at equivalent doses are: HOCl ~ HOBr ~ NHxBry >> OCl-> OBr- >> NHxCly.
  • Chlorinated isocyanurates are common in outdoor swimming pools because they offer resistance to solar decomposition of chlorine residues.
  • Chlorine residues are generally on the order of about 1 part per million, and the pH should be between 7.2 and 7.8. Regular testing to maintain disinfection residues and pH is important.


Dr. Joe Cotruvo is President of Joseph Cotruvo and Associates, LLC, Water, Environment and Public Health Consultants. He is a former director of the drinking water standards division of the EPA.

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