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| United States Patent |
4,594,091 |
| Girvan |
June 10, 1986 |
Borate algaecide and fungicide
Abstract
An algaecide and fungicide comprised of boron derivatives which are added to
standing water systems such as swimming pools, drinking water reservoirs and
cooling towers. The boron derivative algaecide and fungicide is effective in
killing and repressing unwanted algal and fungal growth.
| Inventors: |
Girvan; John W. (5295-6 Western Way
Cir., Jacksonville, FL 32216) |
| Appl. No.: |
583014 |
| Filed: |
February 23, 1984 |
| Current U.S. Class: |
504/151; 514/64 |
| Intern'l Class: |
A01N 059/14 |
| Field of Search: |
71/67,128 514/64
|
References Cited [Referenced
By]
U.S. Patent Documents
| 3560381 |
Feb., 1971 |
Winters et al. |
71/128. |
Other References
The Merck Index (1983), p. 185, entry 1320 and p. 1231,
entry 8421.
Spitieri-Goudeli, Chem. Abst., vol. 98 (1983), 2674v.
Mabrouk, Chem. Abst., vol. 97 (1982), 180396t.
|
Primary Examiner: Mills; Catherine L.
Attorney, Agent or Firm: Jones & Askew
Claims
I claim:
1. A method for controlling algae growth in swimming
pool water comprising adding to said water an effective amount of derivatives of
boron selected from the group consisting of sodium tetraborate and potassium
tetraborate.
2. A method for controlling algae growth in water as in
claim 1 wherein said derivative of boron is sodium tetraborate pentahydrate.
3. A method for controlling algae growth in water is claim 1 wherein
said derivatives of boron are added at a concentratin of between approximately
10 milligrams/liter and 500 milligrams/liter.
Description
TECHNICAL FIELD
The present invention relates generally to the
field of antimicrobial agents and more particularly relates to a method of
killing and repressing algae and fungus growth in standing water such as
swimming pools and drinking water reservoirs and cooling towers.
BACKGROUND OF THE INVENTION
Water is a primary transmission
vector for the spread of potentially dangerous microorganisms. It is also an
excellent growth medium for certain kinds of molds and algae causing unwanted
discoloration and turbidity in the water. Some of the organisms that will grow
in standing water include Chlorococcum, Chlorella, Cledaphora, Microcystis,
Osciliatoris, Spirogyra, Ulaothrix, Vanetteria and the fungus Aspergillus
flavus. Thus, the prevention or inhibition of growth of potentially harmful
microorganisms in water has been a longstanding problem. This is especially true
where there is extensive human contact with the water as in bathing or in
recreational areas such as swimming pools.
The most common prior art
method of water treatment for microorganisms has been to treat the water with
halogens such as chlorine. One way of doing this is to inject elemental chlorine
directly into the water, usually as the water is being filtered. Although
chlorine is an excellent water treatment agent, it has several inherent
problems. One of the major problems is that it is difficult to maintain the
necessary concentration of chlorine in the water to be effective. Chlorine that
is dissolved in water will gradually escape in gaseous form. This loss of
soluble chlorine is accelerated in direct sunlight. Thus, when using this
conventional water treatment method, it is necessary to continuously replace the
lost chlorine. Another disadvantage of using elemental chlorine is that it forms
hydrochloric acid as it dissolves in the water. This causes a drop in the pH of
the water and makes acid-base balancing difficult. Thus, when using chlorine as
a water treatment agent, it is also necessary to add a buffer system to the
water in order to maintain the proper pH.
Chlorine may also be added
directly to water as a powder as a hypochlorite such as sodium hypochlorite.
When hypochlorites are dissolved in water, an equilibrium is set up between free
chlorine and hypochlorous acid. The active ingredient is the elemental chlorine
that is liberated in the equilibrium reaction and is therefore subject to the
same problems as outlined above for free elemental chlorine.
Another
method of controlling water-borne microorganisms is through the use of halogen
substituted organics such as trichloro-S-triazinetrione and
bromochlorodimethylhydantoin. This class of water treatment agents do not
dissipate as rapidly as elemental chlorine and are much easier to handle and to
store. However, they are quite expensive and a buffering system is still
required to maintain a proper pH.
SUMMARY OF THE INVENTION
The
present invention comprises the use of boron derivatives including boric acid,
sodium borates, potassium borates or salts of boron hereafter referred to as
borax and is designed to inhibit algal and fungal growth in water. It is
especially effective in controlling algal growth in swimming pools and in moist
areas such as shower stalls.
The present invention is an advantage over
the prior art in that one application of the borate will prevent the growth of
unwanted algae and molds over a relatively long period of time when compared to
conventional water treatment agents such as chlorine. The present invention is
much more economical than the prior art and is easier to use. For example, in
swimming pools, the present invention may be administered as a water solution
either by injection into the system's filter system or manual addition directly
to the water. The borates may also be added directly to the water as a liquid, a
powder form or a solid form.
In addition to the unexpected algaecidal
and fungicidal activity of the borate derivatives, the compound is an excellent
pH buffer when added as boric acid and the borate salt. For example, if the
boron derivative is added as 1 part sodium tetraborate pentahydrate to 4 parts
boric acid, the resulting solution will be buffered at about pH of 7. Thus, when
using the present invention as an algaecidal agent in a swimming pool there is
no need to add a buffer system such as a carbonic acid-carbonate buffer. In
addition, the boron derivaties cause minimum calcium precipitation, a major
problem in a carbonic acid-carbonate water treatment system. The boron treatment
embodied in the present invention has also been found, in addition to its
algaecidal activity, to enhance the blue color of swimming pools.
Thus
it is a primary object of the present invention to provide a system for the
prevention of growth of algae and molds in water.
It is a further object
of the present invention to provide a system for the economical control of algae
and mold growth in swimming pools.
It is a further object of the present
invention to provide an economical buffer system for maintaining the pH of the
treated water.
It is still a further object of the present invention to
provide an algaecidal system for winterizing swimming pools.
It is a
further object of the present invention to provide a water purification system
for drinking water.
It is a further object of the present inveniton to
provide a colorizing agent for swimming pools.
It is a further object of
the present invention to provide a system for the control of algae in wet areas
such as shower stalls.
These and other objects, features and advantages
will become apparent from a review of the following detailed description of the
invention and the appended drawings and claims.
DETAILED DESCRIPTION OF
THE PRESENT INVENTION
The algaecidal activity of the boron derivatives
was tested using standard pure culture techniques published by the Environmental
Protection Agency TSD designation 6.101. The following testing procedure was
used in all examples.
The standard test organisms are Chlorella
pyrenoidosa, and Chlorococcum mustard. Algae cultures are available froma
Culture Collection of Algae, Department of Botany, Indiana University,
Bloomington, Ind. The algae culture is prepared by adding 30 ml of sterile
Allen's medium (see Allen, M. B., The Cultivation of Myxophyceae, Arch.
Mikrobiol., 17:34-53 (1952) to a 50 ml Erlenmeyer flask. A stock cell suspension
(0.01 ml) is transferred to the flask and is incubated at 22.degree. to
24.degree. C. under 16 hours of fluorescent light for up to four weeks time.
This suspension is used in all tests using C. pyrenoidosa. Other species of
algae used in testing were appropriately identified.
The algaecidal test
was performed by placing 30 ml of Allen's medium into a 50 ml Erlenmeyer flask
using a Brewer Automatic Pipetting Machine. The flasks were then plugged with
cotton and sterilized by autoclaving at 121 degrees centigrade for 20 minutes.
When cooled the flasks were inoculated with C. pyrenoidosa (or other organism)
at a concentration which resulted in an initial organism concentration of
approximately 300,000 cells/ml. All tests were performed with six identical
samples.
Cells were counted using a Spencer Bright Line Hemacytometer.
To determine the algaecidal properties of the borate, 0.01 ml aliquots of the
stock organism were aseptically transferred from the original treated flasks
after two days to six additional 50 ml Erlenmeyer flasks containing 30 ml of
sterile Allen's medium. The cultures were incubated in a controlled environment
chamber under conditions previously described for three weeks. The number of
cells was tested at the beginning of the experiment and at the end of each week.
The amount of algae growth in the test flasks was qualitatively rated as
follows.
0=no visible growth
1=very slight growth
2=slight growth
3=moderate growth
4=heavy growth
5=very heavy growth
For a product to be considered to have a
satisfactory algaestatic activity, it must provide at least 70% control of
growth for three weeks in the original six flasks. Percent control is obtained
by subtracting average rating figure of treated flasks (Rt) from average rating
figure of untreated flasks (Rc), then dividing by the average rating figure of
the untreated flasks (Rc), multipled by 100. ##EQU1##
Algaecidal
activity is defined as no indication of growth in subcultures after three weeks.
EXAMPLE 1
A dose-response curve was performed using Chlorococcum
as the test organism. The test was performed as described above using a control
and six different concentrations of sodium tetraborate pentahydrate (hereinafter
borate) in place of the normal phosphate buffer of Allen's medium. The amount of
algae growth in the test flasks was rated as previously described.
TABLE 1
______________________________________
Borate - mg/l
Control 12.5 5 25 50 100 200 400
______________________________________
1st week
1 1 1 0 0 0 0 0
2nd week
5 3 2 0 0 0 0 0
3rd week
5 5 5 0 0 0 0 0
______________________________________
As shown, a single addition of borate at a concentration of 25
mg/1 or greater completely inhibited any Chlorococcum growth.
EXAMPLE 2
The effect of borate on the growth of the algae chlorococcum mustard and
Chlorella pyrenoidosa and on the mold Aspergillus is shown in this example. The
tests were performed as described above. The borate concentration was 200 mg/1
for all tests.
TABLE 2
______________________________________
Organism
Control Chlorococcum
Chlorella Aspergillus
______________________________________
1st week
1 0 0 0
2nd week
4 0 0 0
3rd week
5 0 0 0
______________________________________
EXAMPLE 3
In this example, the latent effect of inculation
of the organism in borate is measured. The test organism was incubated in the
indicated borate solution for 48 hours and then washed by centrifugation. The
organisms were then resuspended in fresh Allen's medium without borate and
tested weekly for microbicidal and microstatic activity.
Microbicidal
activity was measured as follows:
A=average cell count of control
organisms
B=average cell count of the treated organisms. ##EQU2##
Microstatic activity was measured as follows:
A=average cell
count of control organisms
B=average cell count of the treated
organisms. ##EQU3##
Using the above formulas for calculating the
efficiency of the algaecidal activity, the effect of different concentrations of
borate on Chlorococcum species is shown in the following table. Experimental
conditions are identical to those described previously.
TABLE 3
______________________________________
Borate in mg/l
12.5 25 50 100 200 400
______________________________________
Static 72.7 81.8 100 100 100 100
1st week
Cidal 93.6 93.6 15.3 96.6 97.3 97.3
Static 81.8 90.9 100 100 100 100
1st week
Cidal 74.2 74.2 89.2 90.5 93.2 93.2
Static 63.6 72.7 90.9 100 100 100
1st week
Cidal 0 50.4 72.8 90.4 88.0 92.0
______________________________________
As demonstrated in the above table, a 48 hour exposure of
Chlorococcum species to borate concentrations greater than 50 mg/1 showed
significant algaestatic activity while borate concentrations greater than 100
mg/1 showed significant algaecidal activity even after three weeks.
EXAMPLE 4
The effect of a 48 hour exposure to 200 mg/1 of borate
on several different species of algae and mold is shown in the following table.
The organisms used in this example were Chlorococcum species, Chlorella
pyrenoidosa and Aspergillus flavus. The first two organisms are algae and the
third is a common mold. The same calculations are performed as in Example 4.
TABLE 4
______________________________________
Organism Chlorococcum Chlorella
Aspergillus
______________________________________
Static 100 100 100
1st week
Cidal 89.1 92.8 96.1
Static 100 100 100
1st week
Cidal 91.0 90.71 96.7
Static 100 100 100
1st week
Cidal 90.4 90.4 96.5
______________________________________
As summarized in this table, incubation of the organism in borate
concentrations of o200 mg/1 for 48 hours is highly effective in controlling and
killing the two algae Chlorococcum species and the Chlorella pyrenoidosa and the
mold Aspergilus flavus.
EXAMPLE 5
Boron derivatives can be used
in combination with a sanitizer to treat a water system. Pool sanitizers such as
halogens (chlorine or bromine), copper, hydrogen peroxide, ozone, oxone and
quaternary ammonium compounds. The embodiment of the present invention used in
this example is sodium or potassium tetraborate pentahydrate (hereinafter
borate) in concentrations of about twenty-five mg/liter and bromine (as
bromochlorodimethylhydantoin) in concentrations approximating 0.5 to 1.5
mg/liter. The halogen additive is constantly fed into the pool by standard
procedures well known in the art. The objective in a water treatment system is
to maintain optimal water parameters over a period of time. the optimal
parameters for a swimming pool are approximately as follows:
1. pH--No
change
2. total alkalinity should be held at approximately 200 to 250
ppm
3. Calcium concentration--300 to 350 ppm.
4.
Oxidizer--Bromine (bromochlorodimethylhydantoin) as 0.5 mg/1
Total
Dissolved Solids (TDS) in the water--500 to 000 ppm.
This Example
demonstrates the stability of the borate algaecidal system. In this example, a
thirty thousand gallon pool was monitored from May of 1982 to September of 1982.
The pool was used daily by an average of four bathers for an average of 1 hour
per day. A filter cycle of twelve hours per day was used.
TABLE 5
______________________________________
Test Alk Ca Solid
FAB Borate
date pH ppm ppm ppm mg/l mg/l Algae
______________________________________
5/3 7.3 120 200 750 25 0
5/10 7.7 140 200 750 0.9 25 0
5/17 7.9 150 200 0.7 0
5/24 8.0 160 200 0.5 0
6/7 8.0 165 200 750 0.2 0
6/14 8.0 160 200 0.5 0
6/21 8.0 170 200 0.7 0
6/28 8.0 165 200 0.9 0
7/5 8.0 160 200 0.7 0
7/12 8.0 160 200 0.5 0
7/19 8.0 160 200 0.5 0
7/24 8.0 160 200 0.4 0
8/2 8.0 165 200 3.0 0
8/9 8.0 160 200 0.5 0
8/16 8.0 175 200 0.9 0
8/23 8.0 160 200 0.5 0
8/30 8.0 165 200 0.5 0
______________________________________
EXAMPLE 6
By increasing the borate concentration, the
halogen agent can be completely deleted from the water treatment formula. This
is shown in the results of the field test in Table 6. In this example, a thirty
thousand gallon marblelite pool was monitored from March of 1983 to September of
1983 using only borate as the water teatment agent. The pool was used daily by
an average of four bathers for an average of one hour per day. A filter cycle of
twelve hours per day was used. The borate (sodium tetraborate pentahydrate) was
added to a final concentration of approximately 100 mg/1. Algal growth was
measured visually. No algae growth was visually apparent throughout the test
period.
TABLE 6
______________________________________
Borate Quant.
Test Ca Solid
lbs Acid Ammonia
Al- Bacterial
date pH ppm ppm pounds
HCl oz. gae culture
______________________________________
3-22 8.4 230 600 5 12 0 Neg.
3-28 7.9 240 600 0 0 0 Neg.
4-4 8.0 220 650 0 0 0 Neg.
4-11 7.7 220 550 0 1 0 Neg.
4-18 8.2 250 550 1 0 0 Neg.
4-25 8.2 230 600 5 5 0 Pos.
4-27 40 9.6 0 Neg.
4-28 8.4 248 600 0 0 0 Neg.
4-29 10 0 0 Neg.
5-1 8.5 250 700 27 19.2 0 Pos. Positive
5-2 38 0 0 Neg.
5-3 20 9.6 0 Neg.
5-4 20 0 0 Neg.
5-5 20 0 0 Neg.
5-9 8.6 230 850 3 9.6 0 Neg. Positive
5-16 8.5 242 850 0 9.6 0 Neg.
5-23 8.6 240 800 0 0 0 Neg. Negative
5-24 9.6 0 Neg.
5-30 8.3 240 850 17 9.6 0 Pos. Positive
6-6 8.5 206 750 10 9.6 0 Neg.
6-9 10 0 0 Pos.
6-13 8.4 220 750 0 9.6 0 Neg.
6-20 8.3 196 800 5 4.8 10 Pos. Positive
6-24 5 4.8 10 Pos.
6-27 8.3 200 800 5 4.8 6 Neg.
7-4 8.3 204 800 0 0 6 Neg. Negative
7-11 8.4 200 800 7 0 6 Neg.
7-14 8.3 0 4.8 6 Neg.
7-18 8.3 210 800 0 0 6 Pos. Positive
7-25 8.3 220 800 0 0 6 Neg. Negative
8-1 8.3 210 800 0 0 6 Neg. Negative
8-8 8.3 200 800 0 0 6 Neg. Positive
8-15 8.3 210 800 0 0 6 Neg.
8-22 0 0 6 Neg.
8-29 8.3 210 800 0 0 6 Neg. Negative
9-5 8.3 200 750 0 0 0 Neg.
______________________________________
As shown in Table 6, the present invention was highly effective
even without the addition of a sanitizer. The borate only had to be added as a
result of dilution during filling the pool. Maintenance of the proper pH is
greatly simplified as a result of the high buffering capacity of the present
invention. One can obtain even greater buffering control by adding the borate as
a 1 to 2 ratio of sodium tetraborate pentahydrate to boric acid.
EXAMPLE
7
The control of mold and algae in shower stalls may be accomplished by
making a saturated solution of sodium tetraborate pentahydrate, then spraying it
onto tile and grout surfaces of the stall. The surfaces are then scrubbed with a
fiber brush, resprayed with the borate solution and allowed to stand for 30
minutes. The surface is then washed with water. This procedure is repeated
approximately once a month.
EXAMPLE 8
The present invention can
be used to winterize swimming pools by the following procedure. One week before
the pool is to be closed for the winter, the normal closing procedures are
followed with the additional step of adding borate to a final concentration of
50 mg/1. thereof, it will be understood that variations and modifications can be
effected within the spirit and scope of the invention as described in the
appended claims.
* * * * *
