Here is what appears in Volume 4 Number 2 of the Journal of the Swimming
Pool and Spa Industry:
General:
An Introduction to the Journal
Articles:
John A. Wojtowicz
Chemcon
Cyanuric Acid Technology
Cyanuric acid was identified as a chemical substance over two centuries
ago. However, it was not until the late 1950’s that it attained industrial
significance with the introduction of chlorinated isocyanurates by Monsanto
and FMC. Although the majority of cyanuric acid production is used in the
manufacture of chlorinated isocyanurates, some of it is also used as a swimming
pool available chlorine stabilizer. Cyanuric acid is also used in the manufacture
of specialty intermediates used in the production of plastics and coatings.
The properties, chemistry, uses, etc. of cyanuric acid and chloroisocyanurates
have been comprehensively reviewed (Wojtowicz 1993a and 1993b). In addition
to its function as a stabilizer for available chlorine, cyanuric acid also
contributes to buffering of swimming pool water. This paper discusses the
structure, properties, analysis, chemistry, manufacture, and uses of cyanuric
acid as well as the mechanism of stabilization, the effect on disinfection,
and the effect of chloramine formation.
John A. Wojtowicz
Chemcon
Factors Affecting the Cyanuric Acid Concentrations in Swimming Pools
Use of chloroisocyanurates for swimming pool sanitation results in a
build-up of cyanuric acid (CA) with time. This is a concern because the
kill time of bacteria increases with the ratio of cyanuric acid to free
available chlorine at a given pH (Wojtowicz 1996). This is due to the fact
that cyanuric acid reduces the concentration of hypochlorous acid. The NSPI
(ANSI/NSPI–5 1995) recognizes that cyanuric acid affects the rate of
disinfection by chlorine and recommends higher av. Cl levels for stabilized
pools compared to unstabilized pools, i.e., 1–3 ppm vs. 0.4 ppm. In
fact the NSPI has a draft proposal to raise the ideal recommended av. Cl
range to 2-4 ppm (ANSI/NSPI–4 199X). Excessive concentrations of cyanuric
acid should be avoided, not only to avoid compromising disinfection but
also algae control. Equations for calculating the rate of build-up and
the steady state concentration of cyanuric acid are developed. The NSPI
recommends a maximum of 150 ppm CA and many Health Departments limit CA
in public or commercial pools to 100 ppm because they recognize that CA
affects disinfection. Various options are discussed for limiting or reducing
the cyanuric acid concentration in swimming pools sanitized with chlorisocyanurates,
including water purge, precipitation with melamine, adsorption on activated
carbon, and oxidation with hypochlorite. The most practical method of controlling
or limiting CA build–up is water purging. The loss rate of cyanuric
acid from hypochlorite or chlorine sanitized pools is also discussed.
John A. Wojtowicz
Chemcon
Oxidation of Cyanuric Acid with Hypochlorite
The oxidation of cyanuric acid with available chlorine was studied in
order to determine if excessive levels of cyanuric acid could be reduced
by treatment with hypochlorite. This study showed that prohibitively high
concentrations of available chlorine would be required to achieve significant
reductions in cyanuric acid levels in a practical time. The study also indicates
that the cyanuric acid loss rate under typical swimming pool conditions
is probably not significant.
J. Que Hales, Doug Latta and Kim Skinner
onBalance
A Critique of the Dow Whitney Report
A study was conducted at the University of Florida which concluded that
“deterioration of marcite (including both etching, pitting and staining)
is chemically related and is primarily due to leaching of calcium hydroxide
(portlandite) from the portland cement paste.” However, a close reading
of the draft report itself reveals that no such conclusion can be reached
based on the data published. Indeed, critical data, which would be expected
to support any conclusions made, are missing from the report.
The study was composed of three major components: research and summarization
of pertinent, previously published material; failure analysis of samples
acquired from the industry (referred to as “field diagnostic studies”);
and a lab study designed to replicate field conditions and cause coupons
to exhibit the failure characteristics (referred to as an “etching
and staining mechanistic” study).
The study contains numerous incorrect assumptions, which led to a careful
analysis of the report. It was discovered that many of the incorrect ideas
were plagiarized from material found in an earlier study performed by a
Monsanto employee.
Also, the laboratory study utilizing coupons was duplicated by this paper’s
authors, and the results are given, which indicate that the conclusions
made in the Dow Whitney report about the lab study are unwarranted.