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The use of small streams, dammed up pools along small streams, or small ponds by large numbers of bathers is not generally recommended. Streams and rivers are continuously contaminated by discharges from sewage disposal systems, cesspools, barnyard wastes, and surface draining. Mud bottoms are common which add considerable turbidity to the water, restricting underwater visibility. Streams and ponds must be considered a safety as well as a health hazard.

Small ponds are considered a health hazard because of the small amount of diluting water available. Many authorities are of the opinion that at least 500 gallons of water per bather per day should be available unless chlorination or other disinfection is maintained. Ponds should not be used for public swimming if the surface area is less than 2 acres, or if they contain less than 5,000,000 gallons of water.

Algae growths create a considerable problem in natural bathing areas. Algae give the water an unpleasant appearance, may cause disagreeable odors, and create a turbid condition.

Treatment of large water areas with copper sulfate is not practical.

Unless the water is being chlorinated, no insurance of the safety of the water for swimming can be made. While the bacterial analysis is a helpful guide, it may be of little value in giving a definite opinion as to the freedom of the water from contamination.

This department discourages development of natural bathing areas because of the numerous problems of safety and health encountered.

APPENDIX A-1 OFF SEASON PROTECTION

At the close of the bathing season:

A. The pool equipment should be cleaned and properly stored.

B. The filters should be thoroughly washed and drained so that they will be in a clean condition during the off season.

C. Shut off the water supply and drain all lines and plumbing D. Drain the chemical feeders, hair strainer, and pumps.

E. Store pool ladders and diving boards in a sheltered place. Diving boards should be stored on edge to prevent warping.

F. The electrical service should be cut off and all fuses removed or circuit breakers opened.

Freezing of ground water surrounding the pool is a main consideration for winter protection.

Some authorities maintain that a pool properly constructed and under-drained may be safely left empty over the winter months. Others feel that it is better to keep the pool full of water rather than run the risk of structural cracking resulting from leaving the pool empty. Many authorities recommend that the pool be kept filled with water to a level of about 18 inches below the scum gutter throughout the frost period. Thus, the pressure of the water in the pool would tend to offset the pressure against the sides and bottom. It is desirable in such cases that logs or poles be placed in the water along the sides of the pool to absorb some of the pressure developed by the expanding ice.

If the pool is to remain partially filled for winter, it is recommended that chlorine be added to the water to prevent the growth of algae. If the water is to be used for the following season, addition of chlorine in the fall and spring to eliminate alga problems will make pool start-up much easier.

A-2 POOL LOADING A. Indoor Pools:

(i) Allow 15 square feet of pool surface area per bather where the water depth is less than 5 feet.

(ii) Allow 20 square feet of pool surface area per bather where the water depth is over 5 feet (excluding 300 square feet of pool surface area around each diving board).

B. Outdoor Pools:

(i) Allow approximately 20 square feet of combined pool and walk surface area per bather.

(ii) Diving bays should be restricted to diving only.

A-3 CHEMICAL DOSAGE A. Constants:

1 cubic foot = 7.5 gallons (gals.) 2 gallon of water = 8.34 lbs.

1 ppm = 8.34 lbs. of chemical in 1,000,000 gal.

1% solution (sol.) = 10,000 ppm B. Equations:

(i) Pounds = ______ gal. of water x 8.34 x ppm x 100 1,000,000 x % available chemical substance.

(ii) Ppm = lbs. x 1,000,000 x % available chemical substance Gallons of water x 8.34 x 100

(iii) Pounds = % strength of solution x gal. of sol. x 8.34 % chemical purity

(iv) Gallons of concentrated solution =

Gals of diluted solution x % strength of diluted sol.

% strength of concentrated sol.

(v) Gals. Of = desired dosage (ppm) x gal. of water sol.

% strength of sol. x 10,000

(vi) Application = 0.378 x dosage (ppm) x flow in gpm rate (ppm).

% strength of sol.

C. Examples:

(i) How many pounds of 65% available chlorine are needed to give a 0.8 ppm chlorine residual in 180,000 gallons?

Lbs. = 180,000 gal. x 8.34 x 0.8 ppm x 100 = 1.85 lbs.

1,000,000 x 65% available chlorine

(ii) How many milligrams per liter of a chemical solution would result if 1.5 pounds of gas chlorine were added to 160,000 of water?

Ppm = 1.5 lbs. X 1,000,000 x 100% = 1.12 ppm chlorine 160,000 gal. x 8.34 x 100

(iii) Prepare 5 gallons of 1% chlorine solution from calcium hypochlorite containing 65% available chlorine.

Pounds = 1% x 5 gal. x 8.34 – 0.64 pounds

Required 65%

(iv) Prepare 50 gallons of 1% chlorine solution from sodium hypochlorite containing 5.25% available chlorine.

Gallons of = 50 gal. x 1% - 9.5% gallons 5.25% solution 5.25%

(v) A swimming pool contains 50,000 gallons of water. How much laundry bleach (5.25% chlorine) must be added to the water to obtain a dosage of 2.0 ppm?

Gallons of = 2 ppm x 50,000 gal. – 1.9 gal.

Laundry bleach 5.25% x 10,000

(vi) Determine the number of milliliters per minute of a 2% chlorine solution to be added to a water flow of 275 gpm to obtain a chlorine dosage of 1.5 ppm.

Application = 0.378 x 1.5 ppm x 275 gpm – 78 ml/min Rate (ml/min) 2%

A-4 SUPERCHLORINATION

Approximate chlorine quantities required to establish 8 mg/l: (pt. = pint; gal. = gallon;

oz. = ounce)

Pool Capacity (gallons)

Ordinary Household Bleach (5.25%)

Liquid Chlorine (10%)

Calcium

Hypochlorite (65%) 1,000 1 pt. 0.5 pt. 2 oz.

5,000 5 pt. 2.5 pt. 8 oz.

10,000 1 gal. 2 pt. 5 pt. 1 lb. 0 oz.

15,000 1 gal. 7 pt. 7 pt. 1 lb. 8 oz.

20,000 2 gal. 4 pt. 1 gal. 2 pt. 2 lb. 0 oz.

25,000 3 gal. 1 pt. 1 gal. 5 pt. 2 lb. 9 oz.

30,000 3 gal. 6 pt. 1 gal. 7 pt. 3 lb. 1 oz.

40,000 5 gal. 2 gal. 4 pt. 4 lb. 2 oz.

50,000 6 gal. 2 pt. 3 gal. 1 pt. 5 lb. 2 oz.

A-5 CHLORINATOR SETTINGS

Gas chlorinator settings to feed 1.0 ppm chlorine at various flow rates:

Flow Rate Feed Rate Flow Rate Feed Rate

(gpm) (lbs/24 hour) (gpm) (lbs/24 hour)

10 0.12 160 1.9

20 0.24 180 2.2

30 0.36 200 2.4

40 0.48 220 2.6

50 0.60 240 2.9

60 0.72 260 3.1

70 0.84 280 3.4

80 0.96 300 3.6

90 1.08 325 3.9

100 1.2 350 4.2

120 1.4 375 4.5

140 1.7 400 4.8

To obtain a setting for other than 1.0 ppm, multiply the chart setting by the dosage desired.

A-6 SAFETY RULES FOR GAS CHLORINE EQUIPMENT

A. Be sure of what you are doing when handling chlorine.

B. All threaded fittings and the valve stem have right hand threads. Turn clockwise to close or tighten.

C. Always use a new gasket of standard material for connection of cylinders and equipment.

D. The cylinder valve wrench should be 3/8-inch square box with a maximum length of 6 inches. The wrench shall be left on the valve stem of the chlorine cylinder in use at all times.

E. Frequently check for leaks from the equipment. Locate these leaks by the use of ammonia, not smell.

F. If a chlorine leak is detected, repair it at once. Chlorine leaks get worse with time.

G. Take time to complete the job properly and safely.

H. Keep your eyes open – be alert for danger.

I. Return cylinders to the supplier as soon as they are empty.

J. Remember that you are responsible for the proper operation of the equipment.

A-7 DECHLORINATION

Sodium sulfite, sodium bisulfate, or sodium thiosulfate can be used when it is necessary to de-chlorinate swimming pool water. The dry compounds may be applied by broadcasting evenly over the surface of the pool water. Solutions of the compounds may also be prepared and added to the pool near the inlets to insure mixing.

Sodium sulfite and sodium bisulfites are toxic materials and should be handled with care.

They may react with water to produce toxic and corrosive fumes of sulfur dioxide. Sulfites and bisulfates are rapidly oxidized to sulfates and, when used in proper amounts, should not be hazardous to bathers. Do not, however, permit swimming while de-chlorinating with sulfite compounds.

Sodium thiosulfite is considered low toxic material. The appropriate dosage for removal of 1.0 ppm of excess chlorine is as follows:

Chemical Compound Pounds per 25,000 gallons

Sodium Sulfite 0.75

Anhydrous Sodium Sulfite 0.40

Sodium Bisulfite 0.42

Sodium Thiosulfite 0.25

Example: To remove 8 ppm chlorine from 250,000 gallons of swimming pool water with sodium thiosulfite, how many pounds are needed?

8 ppm x 0.25 lbs x 250,000 gal = 20 pounds 25,000 gal

A-8 TESTING CHLORINE RESIDUALS

Nearly all tests for residual chlorine in swimming pool water are accomplished with a colorimeter, a device that compares colors of solutions with color standards prepared in a laboratory.

Orthotolidine (OTO) has been used for 40 years or more in what is referred to as the flash test method. However, it is obsolete and has been proven to be toxic. Therefore, it has been replaced by a far more accurate and reliable test called the DFD method. DFD, as a liquid or a powder, is the only accurate way to determine chlorine residuals.

The following rules should apply to all chemical testing apparatus:

A. Follow directions carefully. Be particularly accurate in measuring amounts of reagents and in observing time and temperature requirements.

B. Be scrupulously clean. Be sure all solution tubes, eyedroppers, reagent bottles, and equipment are rinsed thoroughly after each use, both inside and outside. Do not handle the equipment with dirty hands. Rinse off

immediately any reagents that touch the skin. Store the equipment, properly boxed or encased, in a clean, protected place. Do not interchange parts such as solution tubes, bottle caps, or droppers.

C. Be sure all reagents are fresh and that the same manufacturer who made the color samples has supplied them. Each manufacturer develops reagents, which are compatible with his/her own instruments, and not all reagents of the same name are of equal composition or concentration. Reagents lose their strength on aging and exposure to light and should not be kept longer than recommended by the manufacturer.

D. Avoid subjecting color standards and reagents to prolonged direct sunlight, or temperatures over 100 degrees or below freezing.

A-9 TESTING pH

The determination of pH is based on the ability of certain organic materials called indicators to change color with the change in acidity or alkalinity of the water. Addition of a small amount of indicator to a sample of the pool water and comparing the color developed with the color standards representing the various pH values permits a rapid measurement of the pH to be made.

Waters containing high free chlorine residuals may have a bleaching effect on the indicator and cause errors in the pH determination. Adding a small crystal of a de-chlorinating agent (about the size of a grain of rice) such as sodium thiosulfate to the sample prior to addition of the indicator will remove the excess chlorine.

The procedure suggested for the pH determination is essentially the same with most test comparisons. Please use the volume of water sample and pH indicator as specified in the test kit instructions.

A-10 BACTERIOLOGICAL TESTING

In the bacteriological analysis of swimming pool water, the laboratory does not attempt to isolate and identify any particular type of disease-producing bacteria. To do this would be a very long and difficult task and the result would not be entirely meaningful. Instead, the lab looks for a particular group of bacteria which is known as coliform bacteria. These bacteria are normally found in the intestines of man and other warm-blooded animals as well as in birds. The presence of such bacteria in water indicates that the water is being contaminated with some sewage-like material. Obviously, such a situation indicates an unsafe condition as disease-producing organisms could be present at any time.

Under Article 13-10 of the Fargo Municipal code, public pool facilities are required to be sampled weekly and monthly for semi-public facilities. A certified laboratory must analyze all samples.

Samples should be collected only when the pool is in use and preferably during periods of heaviest swimmer load. The sampling point should be varied from time to time to obtain a representative cross-section of the sanitary quality of the pool water.

In order to secure a true picture of the condition of the swimming pool water at the time of sampling, sodium thiosulfite is employed to neutralize the chlorine residual in the water during transportation to the laboratory.

To sample the pool, carefully remove the cap from the bottle without touching the inner surface of the bottle or cap. The open bottle is then plunged beneath the surface of the water and swept forward until full. Leave a small air space at the top of the bottle and replace the cap. Do not rinse the bottle with pool water as this will remove the sodium thiosulfite that has been added.

A-11 ENCLOSURE FOR SWIMMING POOL CHLORINATORS

In all pools, where chlorine is supplied by means of a vacuum-operated gas chlorinator, which provides automatic shut off of the gas in case of water pressure failure, a leak, or a break in the chlorine piping, the chlorine cylinders, chlorinator, and all appurtenances shall be located in a separate, reasonably gas-tight, vented enclosure or room. The room shall be at ground level to permit easy access to all equipment. The door of the room should open to the outside and should not open toward the swimming pool or equipment area. The enclosure may be constructed of metal, concrete block or other fire resistant material. A fresh air intake vent shall be installed near the top of the enclosure. A window of at least 18 inches square and artificial illumination shall be provided so the operation of the equipment may be observed at all times without entering the enclosure. Electrical switches for the control of lighting and ventilation shall be located on the outside of the enclosure adjacent to the door.

When the enclosure is part of the filter room or other building, forced air ventilation of the enclosure is required. The exhaust fan shall be capable of one or more air changes per minute. The fan should be equipped with an intake duct extending to near floor level and the air should be exhausted to an outside area where chlorine gas will not create a health hazard.

Please note the following (see illustration on page 46):

A. The chlorine cylinders shall be secured to the enclosure wall with a safety chain to prevent tipping.

B. The chlorine cylinder operating valve shall be opened no more than one quarter to one-half turn.

C. The special wrench for operation of the chlorine cylinder valve shall be attached to the operating stem of the valve at all times.

D. A platform scale shall be supplied for weighing the chlorine cylinder. This is the only way that the operator can determine the amount of chlorine consumed during a 24-hour period.

E. A gas mask approved by the Bureau of Mines for protection against chlorine, or an approved air pack shall be mounted outside the chlorine room.

F. A bottle of ammonium hydroxide shall be available for checking for chlorine leaks.

G. A chlorine cylinder repair kit should be available for emergency use.

A-12 INJECTOR LOCATION FOR VACUUM-OPERATED CHLORINATORS

Most vacuum operated-gas chlorinator problems have been due to improper location of the injector, resulting in insufficient water pressure to develop the necessary vacuum for adequate chlorine flow. The point of chlorine injection on a swimming pool filter re-circulation line should be carefully chosen so that the water pressure at this point is as low as possible. The injector uses a water jet to create a vacuum and will work satisfactorily only if there is enough pressure on the water supply to the nozzle to create a strong jet action.

Adequate pressure for operation of the chlorine injector may be obtained by installing the injector on the suction side of the re-circulation pump and connecting the injector water supply to the pressure side of the re-circulation pump. The pressure differential developed across the pump is more than adequate for proper operation of the gas chlorinator

A-13 RECOMMENDED SWIMMING POOL OPERATIONAL STANDARDS

A. Operate the re-circulation system continuously (24 hours per day) to insure clarity of the pool water.

B. Maintain pH values between 7.4 and 7.8.

C. Maintain a free chlorine residual of at least 1.0 mg/l.

D. Maintain the pool and related facilities in a clean manner at all times.

E. Keep the pool surface free of film and floating dirt and the pool bottom free of sediment.

F. Scrub the bathhouse floors daily with hot soapy water followed by a liberal application of ¼ to 1-% chlorine solution.

G. Inspect all patrons and exclude those showing symptoms of infection.

H. Require all patrons to take a nude shower using warm water and soap before entering the pool.

I. Keep a daily record of operation of the re-circulation system, chemical additions, pH, chlorine residuals, and bathing load.

J. Collect weekly samples of the pool water and submit to the nearest laboratory for bacterial analysis.

THERE IS NO SUBSTITUTE FOR CLEANLINESS

In document UNIVERSIDAD CATÓLICA SANTO TORIBIO DE MOGROVEJO FACULTAD DE INGENIERÍA ESCUELA DE INGENIERÍA CIVIL AMBIENTAL (página 22-0)