BIO201: Biguanide Chemistry

1. BIO201: BIGUANIDE CHEMISTRY
Pool & Spa University

2. WHAT IS BIGUANIDE?
➤ Biguanide’s chemical name is polyhexamethylene biguanide
hydrochloride, or PHMB.
➤ PHMB is a large polymer (chain of repeated molecules) that
also possesses a positive charge, allowing it to crush
organisms (which have negative charges on their cell walls) as
they enter the pool.
➤ Being a polymer like Polysheen® Blue, it also works as an
effective clarifier.
➤ Biguanide is an effective sanitizer but not an effective oxidizer
and requires the use of hydrogen peroxide (H2O2) for
adequate routine oxidation.

3. SANITATION V. OXIDATION
➤ The following is a quick review of sanitation v. oxidation.
➤ Sanitation is defined as the process by which organisms are destroyed. In
pools, this generally refers to killing bacteria and other microorganisms.
➤ Oxidation is defined as the process by which contaminants are chemically
changed (broken down) and removed from the system.
➤ 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.
➤ Only products registered with the EPA are appropriate for use as
sanitizers and oxidizers. BioGuard products are EPA-registered for
use in swimming pools and spas.

4. WHY USE BIGUANIDE?
➤ Systems using PHMB
(SoftSwim®) are completely
chlorine-free.
➤ PHMB is resistant to changes
in water temperature, amount
of sunlight, and shifts in pH; it
requires no stabilizing agents.
➤ Application products are
liquid (this is true for all of
the primary care items in the
SoftSwim® line), removing the
need to predissolve chemicals.

5. SPECIAL CONCERNS WITH BIGUANIDE
➤ As stated previously, biguanide is completely chlorine-free. The
interaction of hypochlorous acid and PHMB produces a sticky,
peanut-butter-like residue in the system that can be difficult to
remove.
➤ Biguanide is metal-intolerant; use of a chelating agent (SoftSwim®
Stain Control) is required in areas where source water contains
metals and only quaternary algicides (SoftSwim® A) may be used
for algae treatment and prevention.
➤ Biguanide pools are more likely to deal with biofilms, a combination
of organisms that can produce, over time, chemicals that break
down some components found in the SoftSwim® product line.
➤ Biofilms will be covered in more detail in a separate course.

6. CONGRATULATIONS!
You have completed the activity!