Pool manufacturers sometimes market their products as being “chemical free.” Chemistry 101 teaches us that claim cannot be true in a literal sense, as all matter–including pool tiles, concrete, plumbing and water–is composed of chemical compounds. But if we assume that the “chemical” of “chemical free” refers to treatment chemicals, such as chlorine and other products added to the water, the question becomes: Can swimming pools go “chemical treatment free”?
Salt water pools use chlorine to destroy germs.通過向鹽水池中的鹽（氯化鈉）施加電量來釋放氯。在傳統的氯化池中，加入氯作為含氯化合物。由於水中存在鈉，鹽水池水可能會感到“絲滑”。
氯or bromine-based sanitizers must be used with UV light.UV is effective against germs including chlorine-resistant parasites likeCryptosporidium.和Giardia，但必須與氯或溴用於殘留衛生。紫外線係統通過循環泳池水，過去紫外線燈，細菌被摧毀。但是，在池的遠處區域中添加的細菌將暴露在紫外線中存在滯後時間。
銅和銀離子具有消毒性質，但自身是緩慢的作用，並且不提供可靠的殘餘物。Therefore, copper and silver ions should be used in conjunction with chlorine, with which they act synergistically to enhance germ destruction.
Pool water must be sanitized to help control the germs introduced by swimmers. Researchersreportthat on average each swimmer introduces 0.14 grams of fecal matter to the pool; for children the amount is likely higher. (That little statistic should encourage swimmers to shower before swimming.)
Recreational water illnesses that can be contracted by exposure to even low levels of fecal matter in the water include diarrhea, swimmer’s ear and various skin infections. Swimming in a pool of water without sanitizer is comparable to immersing oneself into a large communal bath tub with the neighbors. Need more be said about the need to treat pool water by sanitizing it?
Destroying waterborne germs that can make swimmers sick is the goal of swimming pool sanitation. Sanitation can be carried out by adding chemicals or by subjecting pool water to ultra-violet (UV) light. Common sanitizing chemicals include the traditional chlorine-based sanitizers, chlorine generated from salt in saltwater pools, bromine-based sanitizers, copper and silver ions, and ozone gas. The following table provides information on these options.
Common Swimming Pool Sanitizers
|泳池消毒器||Common Name||EPA Registered?||形式||消毒代理人||Provides Residual Protection?||Sensitive to UV Radiation in Sunlight?1|
|穩定氯2||Trichlor and Dichlor||是的||Solid||氯||是的||不|
|未肥胖的氯||Cal-hypo、漂白劑、氯||是的||Solid (Cal-hypo); Liquid (Bleach); Gas (Chlorine)||氯||是的||是的|
|Halohydantoins and Sodium Bromide||是的||Solid||溴||是的||是的|
|Salt Water Pool||Salt pools||不||氯generated by applying electricity to salt water||氯||是的||是的|
|臭氧||臭氧||是的||氣體||臭氧||Very short lived.||是的|
|銅和銀離子||銅，銀||不||Ions from electrolytic erosion of metal||銅銀離子||是的, but slow acting.||不|
All of the sanitizers in the table destroy germs, but only chlorine- and bromine-based sanitizers have staying power, meaning the provision of a reliable fast acting residual that results in continuous, efficient germ control lasting past the time of application. This is of utmost importance because the swimmers themselves introduce an unpredictable load of germs and impurities into the water. When pools are properly maintained—and this includes not only chemical but physical treatment such as filtration—chlorine- and bromine-based sanitizers provide a residual level of protection against the incursion of unwanted substances that can reduce pool water quality and make people sick. That is why many “alternative” pool sanitizers—including ozone, metal ions (minerals) and UV—still require a secondary level of protection, most often provided by chlorine-based sanitizers.
Fred Reiff, P.E., is a retired official from both the U.S. Public Health Service and the Pan American Health Organization, and lives in the Reno, Nevada area.
1Sanitizers that are sensitive to UV radiation in sunlight lose their effectiveness more rapidly than those that are stabilized.