2. SANITATION VS. OXIDATION
ā¤ Chlorine is eļ¬ective as both a sanitizer and an oxidizer. However, these two
functions are distinct.
ā¤ Sanitation is deļ¬ned as the process by which organisms are destroyed. In pools,
this generally refers to killing bacteria and other microorganisms.
ā¤ Oxidation is deļ¬ned as the process by which contaminants are chemically changed
(broken down) and removed from the system.
ā¤ All pools require continuous sanitation and routine oxidation.
Regardless of sanitizer choice, there must always be sanitizer present to
prevent the spread of waterborne illnesses. Oxidation should be performed
on a regular and as-needed basis to reduce contaminant load in the system.
ā¤ Only products registered with the EPA are appropriate for use as
sanitizers and oxidizers. BioGuardĀ® products are EPA-registered for use
in swimming pools and spas.
3. CHLORINE
ā¤ Despite all the diļ¬erent types of chlorine-based compounds available,
the primary sanitizer that results from the introduction of these
products to water is hypochlorous acid (HOCl).
ā¤ Hypochlorous acid is not available to add directly to water for
sanitation; instead, a variety of products, when added to water, result
in hypochlorous acid:
ā¤ Chlorine gas
ā¤ Hypochlorite granules (calcium hypochlorite)
ā¤ Isocyanurates (dichlor and tricolor compounds)
ā¤ Salt, when exposed to an electric current, will also result in
hypochlorous acid by a process known as electrolysis. This process
will be covered later in the course.
4. HYPOCHLOROUS ACID
ā¤ Hypochlorous acid exists in the pool in equilibrium alongside
two ions (particles/molecules with a charge): hydrogen ions
and hypochlorite ions.
HOCL H+ OCL-+
ā¤ As pH increases, the concentration of HOCl molecules decreases and OCl-
ions increases. As pH decreases, the concentration of OCl- ions decreases and
HOCl molecules increases.
ā¤ At a pH of 7.5, the concentration of HOCl and OCl- is equal (50/50). At 7.2,
the concentration shifts to 2:1 in favor of HOCl; at 7.8, 2:1 in favor of OCl-.
ā¤ This is why chlorine is ineļ¬ective at high pH; the HOCl is the actual
chemical doing work, but at high pH levels there is not enough of it to
eļ¬ectively sanitize.
5. HYPOCHLOROUS ACID
ā¤ Hypochlorous acid will react
with a number of diļ¬erent
products in the water to
produce a variety of byproducts:
ā¤ HOCl + nitrogen-based
compounds (like ammonia)
= combined chlorine
(chloramines)
ā¤ HOCl + contaminants =
chloride ion (Cl-), known as
the āsalt formā
ā¤ HOCl + sunlight = chloride
ion (Cl-)
6. WHY HYPOCHLOROUS ACID?
ā¤ Hypochlorous acid is a more eļ¬ective form of sanitizer than any
other type found in pools.
ā¤ Chloramines (combined chlorine) are a sanitizer, but very weak
when compared to hypochlorous acid.
ā¤ Hypochlorous acid is neutral (lacking a charge), making it more
capable of penetrating the cell wall of negatively charged bacteria
than OCl-.
ā¤ Hypochlorous acid is a smaller molecule than those of the various
chloramine compounds, making it easier to diļ¬use through cell
membranes.
ā¤ Monochloramine, in particular, is used to sanitize drinking water
due to its higher stability, but is not as fast as hypochlorous acid.
7. TYPES OF CHLORINE
ā¤ Free available chlorine (FAC/FC/FCL)
ā¤ Measured as the combination of
HOCl and OCl- ions
ā¤ Little to no odor or taste and no
irritation for bathers
ā¤ Combined chlorine (CC)
ā¤ Measurement of chlorine compounds
containing nitrogen, i.e. chloramines
ā¤ Infamous āchlorineā odor
ā¤ Not as eļ¬ective as HOCl as a
sanitizer
ā¤ Total chlorine (TC/TCL)
ā¤ Sum of free chlorine and combined
chlorine
8. CHLORAMINES
ā¤ Chloramines are formed when hypochlorous acid comes into contact with ammonia-
based compounds. Two types of chloramines exist: inorganic and organic.
ā¤ Inorganic chloramines are generally a result of ammonia combining with
hypochlorous acid. Future discussion of chloramines will use this type as an
example.
ā¤ Organic chloramines are generally a result of proteins and amino acids.
ā¤ Inorganic chloramines break down more quickly than organic chloramines;
additionally, organic chloramines are ineļ¬ective as sanitizers.
ā¤ When chloramines are present in the water, undesirable eļ¬ects (skin/eye irritation,
chlorine smell) can result.
ā¤ Chloramines can be removed from the water through breakpoint sanitation or
oxidation.
ā¤ Note that this method diļ¬ers when dealing with chlorine demand; identiļ¬cation
and treatment of chlorine demand will be covered in another course.
9. TYPES OF CHLORINE - NOT RECOMMENDED FOR USE
ā¤ Chlorine gas (Cl-)
ā¤ Produces HOCl and hydrochloric acid (HCl)
ā¤ Lowers pH of water due to HCl
ā¤ Diļ¬cult to handle and store; impractical for most pool applications
ā¤ Sodium hypochlorite (NaClO)
ā¤ Also known as bleach
ā¤ Produces HOCl and sodium hydroxide (NaOH)
ā¤ Raises pH of water due to NaOH
ā¤ Unstable; will break down in container after bottling, reducing eļ¬ectiveness
by as much as half
ā¤ High level of by-products and ļ¬llers raises TDS quickly
ā¤ Weakest available chlorine on the market
10. TYPES OF CHLORINE - UNSTABILIZED CHLORINE
ā¤ Lithium hypochlorite (LiClO)
ā¤ High pH
ā¤ Not as strong as other granular/pressed products, but no additional by-
products added to water
ā¤ Primarily sold as a shock (oxidizer)
ā¤ Calcium hypochlorite (Ca(ClO)2)
ā¤ High pH
ā¤ Slower-dissolving than lithium hypochlorite but delivers more chlorine
(second only to trichlor products)
ā¤ Will raise calcium hardness by 0.8ppm for every 1ppm of HOCl delivered
ā¤ Sold as both a sanitizer and as an oxidizer
ā¤ Active ingredient in CLCĀ®3, CLCĀ® Classic, BurnOutĀ® 3, BurnOutĀ® 73
11. TYPES OF CHLORINE - STABILIZED CHLORINE
ā¤ Stabilized chlorine products are made up of products
containing isocyanurates, which are composed of cyanuric
acid (C3H3N3O3 or (CNOH)ā) and chlorine.
ā¤ The bond formed is not the same as the bonds within
chloramines; the chlorine in the isocyanurate molecule is
still an eļ¬ective sanitizer, whereas the chlorine in the
chloramine molecule is not. Chlorine that is bonded to
cyanuric acid will show up as free chlorine on tests.
ā¤ When bonded to cyanuric acid, chlorine is less susceptible to
breakdown due to sunlight.
12. TYPES OF CHLORINE - STABILIZED CHLORINE
ā¤ Sodium dichloro-s-triazinetrione (C3Cl2N3NaO3)
ā¤ Also known as sodium dichlor or just dichlor
ā¤ Near neutral pH
ā¤ Fast-dissolving
ā¤ Contributes 0.9ppm cyanuric acid (CYA) per 1ppm of free chlorine
ā¤ Sold as both a sanitizer and an oxidizer
ā¤ Active ingredient in Super Solubleā¢, Smart ShockĀ®
ā¤ Trichloroisocyanuric acid ((CClNO)3)
ā¤ Also known as trichlor
ā¤ Low pH
ā¤ Highest concentration of chlorine available (unless blended with other materials)
ā¤ Slow-dissolving
ā¤ Contributes 0.6ppm CYA per 1ppm of free chlorine
ā¤ Sold as a sanitizer
ā¤ Active ingredient in Smart SilkGuardĀ® Sticks, SilkGuardĀ® Sticks, SilkGuardĀ® Tabs, Power Chlorā¢,
BioGuardĀ® Basic Tabs
13. ā¤ Overuse of dichlor and trichlor products can result in high CYA
levels in pools with very little water turnover.
ā¤ High CYA levels will slow down chlorineās ability to kill
bacteria and oxidize contaminants. For 99% of bacteria, this is
not an issue, even at 100ppm of CYA, provided that there is
at least 1ppm free chlorine in the water.
ā¤ For certain water incidents (the primary one being
Cryptosporidium parvum), additional sources of chlorine and
additional time will be needed when CYA is present in the
water.
ā¤ Regular applications of fresh water will keep CYA levels from
increasing rapidly while using dichlor and trichlor products.