FIELD OF THE INVENTION
The present invention provides a method for controlling corrosion, microbial growth, scaling and fouling in water cooled systems. More particularly, it provides a method for controlling corrosion, microbial growth, scaling and fouling in water cooled systems by dispersing Zinc Oxide (ZnO) nanoparticles and Zinc Sulphide (ZnS) nanoparticles in water.

BACKGROUND OF THE INVENTION
Cooling towers are heat rejection or exchange systems. They convectively exchange heat to the atmosphere through cooled water. Some common applications for cooling towers are in industrial air-conditioning systems, water-cooling of equipment and in general manufacturing.
The type of heat rejection or exchange systems in a cooling tower is defined as “evaporative” as it allows moving water streams to provide significant cooling to the rest of the water stream. As this happens, the water in the cooling tower flows and performs the function of heat transfer. This process allows airborne contaminants and particles to become deposited into the cooling water. This, combined with the contaminants in the feed water, creates an environment favorable for microorganism growth, corrosion, solid deposits and scaling.
Microorganisms tend to thrive in the re-circulated water and on wet surfaces. Bacteria, slime and algae foul heat exchanger surfaces and in some cases attack and destroy system components.
Corrosion is caused by the chemicals used for traditional water cooled systems and by chemical reaction of salts in the cooling water. Corrosion impacts on materials of construction and equipments, e.g. cooling towers, heat exchangers, pipelines and other waterside surfaces. Consequently, the result is shortened equipment life, degraded system, increased operating and maintenance costs.
Scaling is primarily made up of salts, more specifically of carbonates of calcium and magnesium. The more the concentration of minerals in cooling water is, the thicker and harder the scale is formed. This becomes very difficult and costly to remove by either physical or/and chemical treatment.
Algae are the most common cause of slime problems in open water systems. They normally grow more profusely on the top deck of cooling towers. The principle threat posed by algae is plugging of tubes, screens and pipelines. As a result, it causes loss of heat transfer efficiency and increased operating cost due to higher pumping power requirements.
Microbial growth, corrosion and scaling result into reduced system efficiency, reduced equipment life and increased labor as well as time for cleaning the system.
Problems encountered in cooling systems are not usually with the equipment, but with the water that is used. The cooling industry must address some major challenges for cooling tower maintenance. They include traditional issues such as 1) controlling scale deposition on cooling system (such as carbonate, sulphate and silica deposits); 2) providing corrosion protection for steel, copper, copper/nickel, and cooper alloys (admiralty) tubes and pipes; 3) controlling microbiological growth, including biofilms on cooling surfaces and bacterial counts in the cooling tower basin water; 4) prevention of fouling in heat exchangers and condenser units; 5) implementation and control must be achievable with a minimum input of labor and money; 6) cost effective as possible considering the total water system capital and operating costs; and 7) must be environmentally acceptable.
Thus, there is a need to develop an approach that protects the water cooling systems from corrosion, microbial growth, foul, and scale deposition; and cost effective, involves less labour and eco friendly.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a method for controlling corrosion, microbial growth, scaling and fouling in water cooled systems by dispersing Zinc Oxide (ZnO) nanoparticles and Zinc Sulphide (ZnS) nanoparticles in water.
Yet another object of the present invention is to provide a method for synthesis of ZnO and Zinc Sulphide (ZnS) nanoparticles.
Yet another object of the invention is to provide a method requiring input for controlling corrosion, microbial growth, scaling and fouling in the water cooled systems.
Yet another object of the invention is to provide a method that performs its cooling function without any hindrance to its functionality.
Yet another object of the invention is to provide a method that involves less labor input and cost effective as the method requires less frequent cleaning of water cooled systems by manual methods.
Yet another object of the invention is to provide a method that is continuous and hassle free and the overall process is not affected by any interruption due to manual cleaning of towers.

SUMMARY OF THE INVENTION
The present invention provides a method for controlling corrosion, microbial growth, scaling and fouling in water cooled systems. More particularly, it provides a method for controlling corrosion, microbial growth, scaling and fouling in water cooled systems by dispersing Zinc Oxide (ZnO) nanoparticles and Zinc Sulphide (ZnS) nanoparticles in water.
In another embodiment of the present invention the present invention provides a method for controlling corrosion and microbial growth, the steps of comprising of:
a) dissolving starch in distilled water forming a starch solution;
b) adding and stirring Zinc nitrate in the starch solution;
c) adding Sodium nitrate solution to starch solution in step b) while stirring constantly to form a mixture;
d) leaving the mixture formed in step (c) for at least 2 hour and allowing the mixture to settle;
e) discarding supernatant solution of the settled mixture;
f) centrifuging the settled mixture obtained in step e) to form nanoparticles;
g) washing nanoparticles with distilled water for at least 3 times;
h) drying the washed nanoparticles at 80°C for overnight; and
i) dispersing the nanoparticles in water;
wherein:
the dispersed nanoparticles in water controls scale deposition;
the dispersed nanoparticles in water controls metal and alloys from corrosion;
the dispersed nanoparticles in water controls microbiological growth, including biofilms; and
the dispersed nanoparticles in water prevents fouling of water.

DESCRIPTION OF THE INVENTION
The present invention now will be described hereinafter with reference to the following description, in which some, but not all, embodiments of the invention are described. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.
Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the invention. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
The present invention provides a method for controlling corrosion, microbial growth, scaling and fouling in water cooled systems. More particularly, it provides a method for controlling corrosion, microbial growth, scaling and fouling in water cooled systems by dispersing Zinc Oxide (ZnO) nanoparticles or Zinc Sulphide (ZnS) nanoparticles in water.
In another embodiment of the present invention the present invention provides a method for controlling corrosion and microbial growth, the steps of comprising of:
a) dissolving starch in distilled water forming a starch solution;
b) adding and stirring Zinc nitrate in the starch solution;
c) adding Sodium nitrate solution to starch solution in step b) while stirring constantly to form a mixture;
d) leaving the mixture formed in step (c) for at least 2 hour and allowing the mixture to settle;
e) discarding supernatant solution of the settled mixture;
f) centrifuging the settled mixture obtained in step e) to form nanoparticles;
g) washing nanoparticles with distilled water for at least 3 times;
h) drying the washed nanoparticles at 80°C for overnight; and
i) dispersing the nanoparticles in water;
wherein:
the dispersed nanoparticles in water controls scale deposition;
the dispersed nanoparticles in water controls metal and alloys from corrosion;
the dispersed nanoparticles in water controls microbiological growth, including biofilms; and
the dispersed nanoparticles in water prevents fouling of water.
In another embodiment of the present invention, the invention provides a method that involves less labor input and cost effective as the method requires less frequent cleaning of water cooled systems by manual methods.
In another embodiment of the present invention, the invention provides a method that is continuous and hassle free and the overall process is not affected by any interruption due to manual cleaning of towers.
Example I:
Dissolving starch (0.1%) in distilled water 500ml by facilitation of microwave oven forming a starch solution; adding Zinc nitrate [14.874 g (0.1 mol)] in the starch solution; stirring the solution for at least an hour by magnetic stirrer until the complete dissolution of Zinc nitrate; adding Sodium nitrate solution drop by drop along the wall of the vessel while constantly stirring; allowing the reaction to proceed for 2 hour; settling the solution for overnight; discarding supernatant solution of the settled mixture; centrifuging the settled mixture at 10,000g for at least 10 minutes to form nanoparticles; washing nanoparticles with distilled water for at least 3 times; drying the washed nanoparticles at 80°C for 6 hours; and dispersing the nanoparticles in water of water cooling system.
The dispersed nanoparticles in water in the cooling systems provide protection to corrosion on steel, copper, copper/nickel, and cooper alloys (admiralty) tubes and pipes in the water cooling systems; control microbiological growth, including biofilms on cooling surfaces and bacterial counts in the cooling tower and basin water; and control scale deposition on cooling system (such as carbonate, sulphate and silica deposits). The above described method is less labor intensive, cost effective and prevents fouling in water cooling systems.

We claim:
1. A method for controlling corrosion and microbial growth comprising the steps of:
a) dissolving starch in distilled water forming a starch solution;
b) adding and stirring Zinc nitrate in the starch solution;
c) adding Sodium nitrate solution to starch solution in step b) while stirring constantly to form a mixture;
d) leaving the mixture formed in step (c) for at least 2 hour and allowing the mixture to settle;
e) discarding supernatant solution of the settled mixture;
f) centrifuging the settled mixture obtained in step e) to form nanoparticles;
g) washing nanoparticles with distilled water for at least 3 times;
h) drying the washed nanoparticles at 80°C for overnight; and
i) dispersing the nanoparticles in non-portable water;
wherein:
the dispersed nanoparticles in water controls scale deposition;
the dispersed nanoparticles in water controls metal and alloys from corrosion;
the dispersed nanoparticles in water controls microbiological growth, including biofilms; and
the dispersed nanoparticles in water prevents fouling of water.
2. The method for controlling corrosion and microbial growth as claimed in claim 1, wherein the solution is stirred by magnetic stirrer.
3. The method for controlling corrosion and microbial growth as claimed in claim 1, wherein the stirring of Zinc nitrate and starch solution formed in step (c) is done until the complete dissolution of Zinc nitrate.
4. The method for controlling corrosion and microbial growth as claimed in claim 1, wherein the centrifugation of settled mixture is done at least 10, 000g for at least 10 minutes.
5. The method for controlling corrosion and microbial growth as claimed in claim 1, wherein the dried nanoparticles are dispersed in water to prevent corrosion and microbial growth.
6. The method for controlling corrosion and microbial growth as claimed in claim 1, wherein the scale deposits that are controlled are carbonate, sulphate and silica deposits.