Here is what appears in Volume 2 Number 1 of the Journal of the Swimming Pool and Spa Industry:

General:

An Introduction to the Journal

The Submission Criterion

Articles:

Michael J. Unhoch, Roy D. Vore, Ph.D., and Peter S. K. Lee, Ph.D.

Zeneca Biocides – Chemical Research and Development Laboratory

Stability of Swimming Pool/Spa Sanitizers: Comparative Chemical Stability of Polyhexamethylene Biguanide and Hypochlorous Acid

Proper hygienic conditions in swimming pools and spas are dependent on the maintenance of a minimal level of disinfectant. The two most common disinfectants/sanitizers in residential swimming pools are polyhexamethylene biguanide (PHMB) and chlorine (HOCl). The stabilities of PHMB and HOCl were compared over the range of temperature, pH, organic load, and sunlight that occur in typical pools and spas. The concentration of bioavailable PHMB was unaffected by temperatures between 39oF and 108oF, pH values between 6.2 and 10.0, and organic load. The quantity of the HOCl available for disinfecting purposes was significantly affected by shifts in temperature and pH. In the presence of ammonia HOCl was converted to less active chloramines. PHMB was not depleted under artificial sunlight levels that caused rapid depletion of HOCl. In practical terms, the PHMB concentrations should be monitored weekly and dosed when the active level falls below the recommended level of 6 ppm. The instability of HOCl mandates that testing and adjustments of levels be performed on a daily basis and, depending on which form and feeding system is used, maintained between 3 and 5 ppm.

Wolfram Hartwig, Ph.D.

Engineered Treatment Systems

To DIN or not to DIN: Ozonation of Pool Water in Public and Commercial Pools

The German pool code, DIN 19643, is a comprehensive standard that regulates all aspects of pool design. It includes ozonation as part of the disinfection and treatment of the pool water. Compliance is mandatory in some, but not all, European countries. Health officials and pool designers in many countries around the world, where ozonation is not covered by existing codes, have accepted DIN 19643 as a guideline. The paper presents some of the basic design concepts of DIN 19643, with emphasis on the ozonation parameters. These are contrasted with US designs, in process applications that employ pre-filter or post-filter injection and full flow or side stream ozonation. Results from several selected sites demonstrate the successful elimination of pool water problems. Recommendations include a list of suggested design dosages based on observations, and additional ozonation design criteria.

John A. Wojtowicz

Chemcon

Relative Bactericidal Effectiveness of Hypochlorous Acid and Chloroisocyanurates

Cyanuric acid stabilizes available chlorine by reducing the concentration of photoactive hypochlorite ion through formation of chloroisocyanurates, which are more stable to sunlight. However, laboratory studies have shown that addition of cyanuric acid reduces the effectiveness of available chlorine as a disinfectant against bacteria. No attempt was made to correlate the kill times with the concentration of biocidal species. The present work was carried out to determine if the decrease in kill rate is due solely to a reduction in hypochlorous acid (a powerful disinfectant) concentration or whether chloroisocyanurates possess significant bactericidal properties. A knowledge of all thirteen equilibrium constants for the cyanuric acid-available chlorine system allows calculation of the hypochlorous acid concentration as a function of pH and the concentrations of total isocyanurate and total free available chlorine. A computer program was employed to calculate the concentrations of hypochlorous acid and the various chloroisocyanurates in the published experimental data on the effect of cyanuric acid on the kill time of bacteria by available chlorine. Statistical analysis showed that the disinfection data correlate excellently with the hypochlorous acid concentration and poorly with the concentration of the various chloroisocyanurates. The primary chloroisocyanurate under typical swimming pool conditions is monochloroisocyanurate ion. Although it is an ineffective bactericide, it allows longer term disinfection in outdoor swimming pools compared to unstabilized available chlorine because it serves as a reservoir of hypochlorous acid, releasing it on demand via rapid hydrolysis.