INVESTIGATING THE USE OF OZONE GENERATORS
TO ENHANCE THE QUALITY AND INCREASE THE
DISINFECTION CAPABILITY OF AUTOMATIC CHLORINE
FEEDERS IN COMMERCIAL APPLICATIONS
OF POOLS AND SPAS

By

Roger L. Phillips Registered Sanitarian
and
Thomas W. Calvin

October 1985

INTRODUCTION

Ozone has been used to treat swimming pools in Europe for nearly 65 years and to purify drinking water for nearly 100 years.

Ozone was first produced under laboratory conditions in 1840. Within a few years, scientists had realized ozone's potential as a disinfectant and it was used to purify the water in swimming pools.

Early ozone generation systems were complex, unreliable and difficult to maintain. They required dangerously high voltage and were expensive to operate. As a result, less expensive chlorine became the standard for purification. Recent technological advances in electronics have lowered the cost of ozone generation.

OBJECTIVE

Tests were run on October 2, 3, and 10, 1985 to investigate the use of ozone generators to enhance the water quality and increase the disinfection capability of automatic chlorine feeders in commercial applications of pools and spas.

OZONE

Ozone can best be described as "energetic" oxygen. Ozone is formed when three atoms of oxygen are bound together instead of the normal two atoms. This extra oxygen atom makes ozone a highly energetic oxidizer and a very efficient natural purifying agent.

In nature, ultraviolet rays striking the earth's upper atmosphere generate ozone. This natural phenomenon can be duplicated by placing an ultraviolet arc lamp in an ozone generation chamber.

Ozone purifies by oxidizing all contaminants. It pierces the cell wall of microorganisms (bacteria, virus, algae) on contact, thus destroying them. It bonds with minerals, forming them into oxides which clump together for easy removal by the filter system. Ozone oxidizes perspiration, urine, body oils, suntan lotions, cosmetics and other pool and spa contaminants, reducing them to carbon dioxide. (However, before spa contaminants reach that point, the intermediate oxidation products are usually gathered into flocculent masses and removed by the filter of the pool or spa).

GENERATION

The Prozone unit, which was used in this testing, works as air is pumped through it by a compressor attached at the air inlet end. A high-energy ultraviolet light converts some of the air to ozone and feeds this air through the return water line to the pool. (See diagram #2)

The ultraviolet source is a very special gaseous arc lamp designed for efficient ozone generation. The arc is contained within a special pure glass tube which allows the high-energy ultraviolet light to be transmitted as efficiently as possible.

The ozone-enriched air is removed at the point where the highest concentration of UV exists within the chamber. Air entering the ozone generator is filtered to remove dust which could possibly contaminate the inside of the chamber.

MATERIALS USED

(1) Prozone PZ II-1 ozone generator

(2) Comfortime 225 gallon hot tubs which were equipped with 3/4 H.P. pumps, Dynamic 25 square foot in line cartridge Filters and heaters.

(1) Lifegard #300-19 Chlorinator.

(10) Swim Chem Hi Tabs chlorine tabs 70 oz. Active ingredient: Trichloro-s-Triozinetrione (Available Chlorine 90%).

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TEST RESULTS

Inoculation tests results for each of the four runs (sampled at 1 hour and 2 hour intervals). The test results for E-Coli bacteria are expressed as number of organisms per ml.

Test run #1 (Control Spa)

Sample #	Temp F	pH	Time	No. of E-Coli per ml
1	103	7.4	1 hr.	5000
2	104	7.4	2 hr	3800

Test run #2 (chlorine and ozone)

Sample #	Temp F	pH	Time	No. of E-Coli per ml
1	103	7.4	1 hr	6000
2	104	7.4	2 hr	6000

Test Run #3 (Chlorine)

Sample #	Temp F	pH	Time	No. of E-Coli per ml
1	104	7.2	1 hr	3000
2	104	7.2	2 hr	3100

Test Run #4 (Ozone)

Sample #	Temp F	pH	Time	No. of E-Coli per ml
1	104	7.2	1 hr	500
2	104	7.2	2 hr	800

Test results after introduction of a disinfectant in three of the spas that were run after the two hour inoculation period. Six Samples were taken at the following intervals: 15 minutes, 25 minutes, and at 40 minute intervals thereafter.

Test Run #1 (Chlorine and ozone)

Sample #	Temp F	pH	Time	PPM Chlorine	No. of E-Coli per ml
1	103	7.4	15 min.	0.0	1300
2	103	7.4	40 min.	1.5	less than 10
3	103	7.4	80 min.	1.5	less than 10
4	103	7.4	120 min.	1.5	less than 10
5	103	7.4	160 min.	2.0	less than 10
6	103	7.4	200 min.	2.0	less than 10

Test Run #2 (Chlorine)

Sample #	Temp F	pH	Time	PPM Chlorine	No. of E-Coli per ml
1	104	7.4	15 min.	0.0	1200
2	104	7.4	40 min.	0.0	1200
3	102	7.6	80 min.	0.0	1200
4	105	7.6	120 min.	0.0	1200
5	102	7.6	160 min.	0.6	less than 10
6	104	7.8	200 min.	3.0	less than 10

Test Run #3 (Ozone)

Sample #	Temp F	pH	Time	PPM Chlorine	No. of E-Coli per ml
1	104	7.4	15 min.	0.0	10500
2	104	7.4	40 min.	0.0	1600
3	102	7.6	80 min.	0.0	1200
4	105	7.6	120 min.	0.0	170
5	103	7.6	160 min.	0.0	50
6	104	7.8	200 min.	0.0	80

Test results of Control Spa run and sampled at same intervals as disinfected spas.

Sample #	Temp F	pH	Time	PPM Chlorine	No. of E-Coli per ml
1	1.3	7.4	15 min.	0.0	4200
2	102	7.4	40 min.	0.0	4500
3	103	7.4	80 min.	0.0	4700
4	103	7.4	120 min.	0.0	5000
5	103	7.6	160 min.	0.0	8000
6	103	7.6	200 min.	0.0	10500

Note: Chlorine tablets were weighed after a period of drying time from the end of each run. The difference in weight was expressed in ounces and used to estimate the quantity of chlorine consumed.

Test Run #1- 26 ounces

Test Run #2- 6 ounces

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METHODS

Two identical spas were filled with City of Phoenix tap water The water was held in each spa for twenty hours before being inoculated An E-Coli Water Suspension was prepared by a certified laboratory at a concentration of 10 to 10 organisms per 100 ml. At the beginning of all test runs the water temperature was 103 degrees to 104 degrees F. The spas were held for two hours from the time E-Coli bacteria was introduced without the addition of Chlorine or Ozone. The pH was adjusted to 7.4 by the addition of a 28% solution of HCL. The water was sampled at the end of the first and second hours.

This experiment included four test runs of the following: 1 control; simultaneous introduction of chlorine and ozone; introduction of chlorine only; and introduction of ozone only. A series of grab samples were taken, each one near the geometric center of the water body. Samples were collected in sterilized plastic containers, refrigerated and delivered to the laboratory where they were analyzed for concentration of E-Coli bacteria. Procedures described in "Standard Methods for the Analysis of Water and Wastewater" were used. Time intervals for all samples after the initial two hour inoculation and 40 minutes thereafter for a total of six samples.

At the beginning of the test run (chlorine and ozone) the chlorine metering device was set at the lowest setting. At the end of sample #1 the setting was turned to maximum At this time the residual chlorine reached 1.5 P.P.M. and the chlorine meter was then turned to the off position. The chlorine residual continued to rise and stabilized 1.5 hours later at 2.0 P.P.M.

At the end of the first two test runs both spas were cleaned with a 2% solution of Sodium Hypochlorite and carefully rinsed with clean tap water.

CONCLUSIONS

The data collected in the field and results of controlled laboratory analysis indicates the following:

1. The use of chlorination with ozonation is a more effective method for the disinfection of spas than the use of chlorine.

2. When ozone is used in conjunction with chlorine, a chlorine Residual is established significantly faster and is more easily maintained than with the use of chlorine alone.

3. The chlorine demand should have been less for the spas tested then would be expected for a typical commercial spa. Most of the B.O.D. in the test spas was from the introduction of coliform organisms and the clean tap water was retained for a relatively short time.