Technical How-to - swimming pool non chlorine treatment purification specialist

THE AQUABRITE SYSTEM
Chedzoy R.L., Caiger E.J., Hakimi F.

TABLE OF CONTENTS

Introduction
PH and Alkalinity
Organic and Nitrogen Content
Ultra-Violet Light and Temperature
Application of Chlorine

Introduction
Copper
Silver
Aquabrite Oxidiser
Advantages of The Aquabrite System
Application of The Aquabrite System

METHODOLOGY

Experimental Design
Choice of Challenge Organisms
Analytical Methods
Chemical
Microbiological or Biocidal Efficacy Test Methods
Quality Assurance and Quality Control

DISCUSSION OF RESULTS

BIBLIOGRAPHY

Appendix 1 Chemical Analyses of Water
Appendix 2 Biocidal Efficacy Test Methods
Appendix 3 Biocidal Efficacy Results

- SUMMARY -

The Aquabrite System is a non-chlorine, fresh water method of disinfection of swimming pools. The latest efficacy trials investigated bacterial mortality against time using an improved formulation. Mortality rates for chlorine against time were also examined. Organisms from two sources, laboratory cultures and raw sewage were used to assess die-off rates. The Aquabrite System was highly effective in promoting bacterial mortality from both sources. Chlorine displayed less rapid efficacy on laboratory cultured organisms and no demonstrable die-off was observed on raw sewage bacteria during the test period. This paper attempts to cover the following objectives:

Report recent efficacy trials investigating bacterial mortality against time, using The Aquabrite System, incorporating a new formulation.

Describe The Aquabrite System, its applications and unique advantages as a practical pool disinfectant.

To compile and summarise available background data on the development of The Aquabrite system.

BRIEF REPORT

The data obtained by this series of controlled tests indicated that when a low level of a specially blended persulphate oxidiser was used with copper and silver ions in water containing urea (organic nitrogen) excellent results were obtained. Chlorine, under similar circumstances, did not perform as well, probably due to the formation of chloramines. In heavily used swimming pools, the water will certainly contain ammonia and urea so that these compounds will be present in the pool water. Unless large quantities of chlorine are being continuously added to achieve the desired free chlorine concentration then inadequate disinfection will result. Public pools often have such a facility but domestic pools do not. It is in such circumstances that The Aquabrite System can be of benefit.

The Aquabrite System displayed the additional benefit of longevity of antimicrobial activity. This was demonstrated by storing treated water for fourteen days before conducting mortality versus time tests using Ps.aeruginosa sp as the test organism.

THE CHLORINE TREATMENT SYSTEM

- Introduction -

Historically chlorine has been favoured as a water disinfectant. It exhibits rapid bactericidal activity within certain constraints. The efficacy of chlorine is limited by pH, alkalinity (ability of the water body to resist changes in pH), organic content, nitrogen content and exposure to ultra-violet light (White, 1972).

These conditions do not often receive the attention required to maintain the efficacy of chlorine. The dosing of chlorine into water with an incorrect balance of the above mentioned parameters may lead the operator into a false sense of security. These parameters are discussed below.

- pH and Alkalinity -

Chlorine is only effective as a disinfectant when in the form of hypochlorous acid (HOCl). This form of chlorine exists when the pH of the water body is less than 9.0. Above pH 9.0 the hypochlorite ion (OCL) predominates. Hypochlorite ion, at concentrations normally found in swimming pools, is a very poor sanitizer (White, 1972). Refer to table below:

pH	*HOCl%*	*OCl%*	*@ 20 C*
*5.0*	*99.7*	*0.3*
*6.0*	*96.8*	*3.2*
*7.0*	*75.2*	*24.8*
*8.0*	*23.2*	*76.8*
*9.0*	*2.9*	*97.1*

Content of HOCl decreases with increase in pH and content of OCl increases with increase in pH (White, 1972).

Spas may be particularly prone to unstable pH as the large volume of air injected through the water in a spa may cause carbon dioxide stripping of the water. Loss of carbon dioxide causes a rise in pH. At a given temperature and pressure, carbon dioxide is in fixed equilibrium with bicarbonate ion in the water.

HCO3- ------> OH- + CO2 (gas)
(bicarbonate) (hydroxide) (carbon dioxide

From the reaction above it is apparent that the removal of carbon dioxide forces the equilibrium to the right, causing the formation of the alkali hydroxyl ion which increases the pH.

- Organic and Nitrogen Content -

The concentration of nitrogen (as ammonia and urea) and organic matter present in pool water is of critical importance. The active form of chlorine, hypochlorous acid (HOCl), is an extremely reactive chemical and is able to combine with these constituents to form a wide variety of compounds. Some of these compounds are toxic and irritating.The hypochlorous acid which combines in this way is rendered less effective as a disinfectant. In order to maintain appropriate conditions the water body must remain essentially free of constituents which will combine with chlorine; however these are often difficult to control. Nitrogen may enter the water in the form of urea from urine and sweat, sun screen lotion and quaternary ammonium algicides. Organic matter may enter the water through leaves, dust, skin cells, make up and faeces. Urea, a component of urine, is the main source of ammonia nitrogen. Urea is converted to ammonia by hydrolysis with water under the influence of the urease enzyme in the following way.

               urease
NH2 - CO - NH2 + H2O      ----->         2NH3 + CO2
        (urea)                        enzyme        (ammonia)

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