MXPA98002441A - Methods and compositions to control bioincrustation using tiou compounds - Google Patents

Abstract

The present invention relates to a method for inhibiting the adhesion of bacteria to a submergible surface. The method contacts the submergible surface with an effective amount of at least one thiourea to inhibit bacterial adhesion to the submergible surface. The present invention relates to a method for controlling the biofouling of an aqueous system. This method adds an effective amount of at least one thiourea to inhibit bacteria from adhering to a submerged surface within the aqueous system. This method effectively controls biofouling without substantially killing the bacteria. The thiourea used in the method of the invention is a compound of the formula (I). The present invention also relates to compositions containing thiourea compounds and which can be used in the above methods. The compositions comprise at least one thiourea in an amount effective to inhibit bacteria from adhering to submergible or submerged surfaces.

Description

METHODS AND COMPOSITIONS FOR CONTROLLING BIOINCRUSTATION USING THIOUREA COMPOUNDS DESCRIPTION OF THE INVENTION The invention uses thiourea compounds to inhibit bacterial adhesion to submergible or submerged surfaces, particularly those surfaces within an aqueous system. The invention also relates to methods and compositions for controlling biological fouling. Microorganisms adhere to a wide variety of surfaces, particularly surfaces in contact with aqueous fluids that provide an environment suitable for microbial growth. For example, it is known that microorganisms adhere to ship hulls, marine structures, teeth, medical implants, cooling towers and heat exchangers. Adhering to such submerged or submerged surfaces, microorganisms can embed themselves to the surface or cause their deterioration. In mammals (eg, humans, cattle, pets), microorganisms attached to a surface can lead to health problems. For example, the plaque results from microorganisms that adhere to the surfaces of the teeth. Medical implants with unwanted microorganisms attached to their surfaces are often covered with crusts and must be replaced.

Scientific studies have shown that the first stage of biofouling in aqueous systems is generally the formation of a thin biological film on submerged or submergible surfaces, that is, surfaces exposed to the aqueous system. By joining and colonizing on a submerged surface, microorganisms such as bacteria are generally thought to form the biological film and modify the surface in favor of the development of the more complex community of organisms that form the advanced biofouling of the aqueous system and its surfaces submerged A general review of the mechanisms of the importance of biological film, the initial stage in biological encrustation is given by CA Kent in "Biological Fouling: Basic Science and Odels" (in Meló, LF Bott, TR, Bernardo, CA (eds. ), Fouling Science and Technology, NATO ASI Series, E Series, Applied Sciences: No. 145, Klu er Acad. Publishers, Dordrecht, The Netherlands, 1988). Other literature references include M. Fletcher and G. I. Loeb. Appl. Environ. Microbiol. 37 (1979) 67-72; M. Humphries et al., FEMS Microbiology Ecology 38 (1986) 299-308; and M. Humphries et. al., FEMS Microbiology Letters 42 (1987) 91-101. Biofouling, or biological fouling, is a persistent nuisance or problem in a wide variety of aqueous systems. Biofouling, both incrustation microbiological as acrobiological is caused by the accumulation of microorganisms, macroorganisms, extracellular substances and dirt and debris that are trapped in the biomass. The organisms involved include microorganisms such as bacteria, fungi, yeasts, algae, diatoms, protozoa, and macroorganisms, such as macroalgae, barnacles, and small molluscs such as Asian clams or zebra mussels. Another phenomenon of objectionable biofouling that occurs in aqueous systems, particularly in fluids of aqueous industrial processes, is the formation of lama. Lama formation can occur in fresh, saline or saltwater systems. The lama consists of entangled deposits of microorganisms, fibers and debris. It can be fibrous, pasty, rubbery, tapioca-like or hard and has an undesirable characteristic odor that is different from the aqueous system in which it is formed. The microorganisms involved in lama formation are mainly different species of spore-forming bacteria and bacteria that do not form spores, particularly encapsulated forms of bacteria that secrete gelatinous substances that cover or enclose the cells. The microorganisms in the lama also include filamentous bacteria, filamentous mold-like fungi, yeast, and yeast-like organisms.

Biofouling, which often degrades an aqueous system, can manifest itself as a variety of problems, such as loss of viscosity, gas formation, objectionable odors, decreased pH, color change and gelling. Additionally, the degradation of an aqueous system can cause the incrustation of the related water management system, which may include, for example, cooling towers, pumps, heat exchangers, and pipes, heating systems, gas separation systems. and other similar systems. Biofouling can have a direct adverse economic impact when it occurs in industrial process waters, for example, cooling waters, metalworking fluids or other water recirculation systems, such as those used in papermaking or manufacturing. textiles If left unchecked, the biological fouling of industrial process waters can interfere with the process operations, decrease the efficiency of the process, waste energy, clog the management system and water, and even degrade the quality of the product. For example, water cooling systems used in power plants, refineries, chemical plants, air conditioning systems and other industrial operations often encounter biofouling problems. The air organisms that entered from the Cooling towers, as well as the water bodies of the system water supply, commonly contaminate these aqueous systems. Water in such systems generally provides an excellent growth medium for these organisms. Aerobic and heliotropic organisms develop in the towers. Other organisms grow and colonize such areas as the tower collector, pipes, heat exchangers, etc. If left unchecked, the resulting biofouling can block the towers, block the pipes and coat the heat transfer surfaces with layers of lama and other biological fibers. This prevents proper operation, reduces cooling efficiency and, perhaps most importantly, increases the costs of the overall process. The industrial processes subject to biofouling also include paper-making, the manufacture of pulp, cardboard, etc., and the manufacture of textiles, particularly non-woven textiles laid in water. These industrial processes generally recirculate large quantities of water under conditions that favor the growth of biofouling organisms. Papermaking machines, for example, handle very large volumes of water in recirculation systems called "white water systems". The provision to a paper machine usually contains only about 0.5% solids to form fibrous and non-fibrous paper, which means that for every 1.00O kg of paper, almost 200,000 kilograms of water pass through the upper box. Most of this water is recirculated in the white water system. White water systems provide excellent growth medium for biofouling microorganisms. This growth can result in the formation of lama and other deposits in upper boxes, water lines and paper forming equipment. Such biofouling can not only interfere with water and raw material flows, but when it is released, it can cause stains, holes and odors in the paper, as well as mesh structures, costly interruptions in the operations of the paper machinery. The biofouling of recreational waters, such as swimming pools or spas, or decorative waters such as wells or fountains, can severely retract people's enjoyment of them. Often, biological embedding results in objectional odors. More importantly, particularly in recreational waters, biofouling can degrade the water quality to such an extent that it is not suitable for use and may even pose a health risk. Sanitation waters, such as industrial process waters and recreational waters, are also vulnerable to biofouling and its associated problems. The waters of sanitization include toilet water, cistern water, septic water and drainage treatment water. Due to the nature of the effects contained in sanitization waters, these water systems are particularly susceptible to biofouling. To control biofouling, the technique has traditionally treated a water system affected with chemicals (biocides) in concentrations sufficient to kill or greatly inhibit the growth of biofouling organisms. See, for example, U.S. Patent Nos. 4,293,559 and 4,295,932. For example, chloride gas and hypochlorite solutions made with gas have been added for some time to water systems to kill or inhibit the growth of bacteria, fungi, algae or other problematic organisms. However, chlorine compounds can not only damage the materials used for the construction of aqueous systems, they can also react with organic materials to form undesirable substances in effluent streams, such as chloromethanes and chlorinated carcinogenic dioxins. Certain organic compounds such as methyl bisthiocyanate, dithiocarbamates, haloorganics, and quaternary ammonium surfactants have also been used. While many of these are very efficient at killing microorganisms or inhibiting their growth, they can also be toxic or harmful to humans, animals or other organisms that are not white. One possible way to control the biofouling of aqueous systems, which includes the associated submerged surfaces, could be to prevent or inhibit bacterial adhesion to submerged surfaces within the aqueous system. This can be done, of course, using bactericides, which, however, generally suffer from some of the disadvantages mentioned above. As an alternative, the present invention provides methods and compositions useful for substantially inhibiting bacterial adhesion to a submerged or submergible surface. The invention makes obvious the disadvantages of previous methods. Other advantages of this invention will be apparent from a reading of the specifications and appended claims. The present invention relates to a method for inhibiting bacteria from adhering to a submergible surface. The method contacts the submersible surface with an effective amount of at least one thiourea to inhibit bacteria from adhering to a submergible surface. The thiourea used in the method has the following formula: The substituents R.sub.1 and R.sub.2 can each independently be an alkyl group of C.sub.1 -C.sub.i -j or R.sub.1 and R.sub.2 together with the nitrogen atom which bears them, form a 5-8 membered heterocyclic ring of the formula: In the heterocyclic ring, X can be 0, NH, or CH2; R5 can be methyl, hydroxymethyl, hydroxyethyl, or halo; and n ranges from 0 to 3. The substituent R3 is a C1-C7 alkyl group and R4 is hydrogen. The present invention also relates to a method for controlling the biofouling of an aqueous system. This method adds an aqueous system an effective amount of at least one thiourea, described above to inhibit the adherence of bacteria to submerged surfaces within the aqueous system. This method effectively controls biofouling without killing substantially the bacteria. The present invention also relates to a composition for controlling the biofouling of an aqueous system. The compositions comprise at least one thiourea in an amount effective to inhibit the adhesion of the bacteria to a submergible surface or a submerged surface within an aqueous system. In one embodiment, this invention relates to a method for inhibiting adhesion of submersible bacteria. A submersible surface is one that may be covered, overflowed or moistened, at least partially with a liquid such as water or other aqueous liquid fluid. The surface may be intermittently or continuously in contact with the liquid. As discussed aboveExamples of submersible surfaces include, but are not limited to, ship hulls or boats, maritime structures, teeth, medical implants, surfaces within an aqueous system such as the inside of a pump, pipe, cooling tower or heat exchanger. A submersible surface can be composed of hydrophobic, "hydrophilic or metallic materials Advantageously, using thiourea compounds according to the invention, the adhesion of bacteria to hydrophobic, hydrophilic or metallic submergible or submerged surfaces can be effectively inhibited.

To inhibit the adhesion of a bacterium to a submergible surface, the method contacts the submergible surface with a thiourea. The surface is contacted with an effective amount of a thiourea, or mixture of thiourea compounds, to inhibit the adhesion of microorganisms to the surface. Thiourea can be applied to the submergible surface using means known in the art. For example, as discussed above, thiourea can be applied by spraying, coating or submerging the surface with a liquid formulation containing the thiourea. Alternatively, the thiourea can be formulated into a paste which is then dispersed or brushed on the submergible surface. Advantageously, the thiourea may be a component of a composition or formulation commonly used with a particular submergible surface. "Inhibiting the adhesion of bacteria" to a submergible surface means allowing a small or insignificant amount of bacterial adhesion for a desired time. Preferably, the adhesion of bacteria is not essentially present and is more preferably avoided. The amount of thiourea employed should allow only poor or insignificant bacterial adhesion and can be determined by routine tests. Preferably, the amount of thiourea used is sufficient to apply at least one monomolecular film of thiourea to the Submersible surface. Such a film preferably covers the entire submergible surface. By contacting a submergible surface with a thiourea according to this method, the surface is allowed to be pre-treated against bacterial adhesion.

Consequently, the surface can be brought into contact with the thiourea cradle when immersed in an aqueous system. The present invention also relates to a method for controlling the biofouling of an aqueous system. An aqueous system comprises not only the embedding of fluids or liquids through the system, but also the submerged surfaces associated with the system. Submerged surfaces are those surfaces in contact with the fluid or aqueous liquid. As the submersible surfaces discussed above, the submerged surfaces include, but are not limited to, the internal surfaces of pipes or pumps, the walls of a cooling tower or upper case, heat exchangers, screens, etc. In short, the surfaces in contact with the "aqueous fluid or liquid are submerged surfaces and are considered part of the aqueous system The method of the invention adds at least one thiourea to the aqueous system in an amount that effectively inhibits bacteria from adhering to a submerged surface within the aqueous system. used, this method effectively controls the biofouling of the aqueous system without substantially killing the bacteria. "Biofouling control" of the aqueous system means controlling the amount or degree of biofouling to, below a desired level and for a desired time for the particular system. This can eliminate biofouling of the aqueous system, reduce biofouling to a desired level, or completely avoid or above the desired level of biofouling. In accordance with the present invention, "inhibiting the adhesion of bacteria" to a submerged surface within the aqueous system means allowing a small or insignificant amount of bacterial adhesion for a desired time for the particular system. Preferably, essentially no bacterial adhesion is present and more preferably bacterial adhesion is avoided. Using a theory according to the invention, in many cases it is possible to break or reduce other attached microorganisms - existing to undetectable limits and maintain that level for a significant time. While some thiourea compounds may exhibit biocidal activity at concentrations above certain threshold levels, thiourea compounds effectively inhibit bacterial adhesion at concentrations generally below such threshold levels. According to the invention, thiourea inhibits bacterial adhesion without substantially killing the bacteria. Therefore, the effective amount of a thiourea used according to the invention is below its toxic threshold, if the thiourea also has biocidal properties. For example, the concentration of thiourea may be ten or more times below its toxic threshold. Preferably, thiourea should also not harm non-white organisms, which may be present in the aqueous system. A thiourea, or a mixture of thiourea compounds, can be used to control biofouling in a wide variety of aqueous systems such as those previously discussed. These aqueous systems include, but are not limited to, industrial aqueous systems, aqueous sanitation systems, and aqueous recreational systems. As discussed above, examples of industrial aqueous systems are fluids for metalworking, cooling waters (e.g., consumption cooling water, effluent cooling water, and recirculating cooling water) and other recirculating water systems such like those used in the formation of paper and textile manufacture. Aqueous sanitation systems include wastewater systems (eg, industrial, municipal and private wastewater systems), bathrooms, and water treatment systems, (for example, drainage treatment systems). Swimming pools, fountains, ornamental or ornamental pools, wells or streams, etc., provide examples of recreational water systems. The effective amount of a thiourea to inhibit bacteria from adhering to a submerged surface in a particular system will vary somewhat depending on the aqueous system that will be protected, the microbial growth conditions, the degree of any biofouling there is, and the degree of control of desired biofouling For a particular application, the amount of choice can be determined by routine testing of several quantities before treatment of the entire affected system. In general, an effective amount used in an aqueous system may vary from about 1 to about 500 parts per million and more preferably from about 20 to about 100 parts per million of the aqueous system. The thiourea compounds employed in the present invention have the following general formula: The substituents R1 and R2 can each independently be an alkyl group of C ^ -Ci-j, preferably an alkyl group of 3-C10- The alkyl group can be branched or unbranched. More preferably, R1 and R2 are a straight chain propyl or octyl group. Alternatively, R2 and R2 together with the nitrogen atom carrying them form a 5-8 membered heterocyclic ring of the formula: The group X can be 0, NH, or CH 2 • The substituent R 5 can be methyl, hydroxymethyl, hydroxyethyl, or a halo group such as a chloro group. The integer n may vary from 0 to 3 and preferably 0 or 1. Preferably the heterocyclic ring is a 5- or 6- membered ring. Specific preferred rings include piperidinyl, methyl-piperidinyl, dimethylpiperidinyl, hydroxymethylpiperidinyl, dichloropiperidinyl, hexamethyleneiminyl, and morpholinyl. The group R3 can be a C? -C7 alkyl group, branched or unbranched. R3 preferably is a C3-C5 alkyl group and more preferably an n-butyl group. The substituent R4 is hydrogen.

Preferred thiourea specific compounds of the above formula include: n-butyl-N ', N' -dicyclohexylthiourea, compound (a), -n-butyl-N ', N' -dioctylthiourea, compound (b); n-butyl-N '-hexamethyleneiminothiourea, compound (c); n-butyl-N '-3-methylpiperidinothiourea, compound (d), - n-butyl-N'-2-methylpiperidiniothiourea, compound (e); n-butyl-N '-morpholinothiourea, compound (f) n-butyl-N' -3,5-dimethylpiperidiotiourea, compound (g); and n-butyl-N ', N' -dipropylthiourea, compound (h). The thiourea compounds can be prepared by reacting a secondary amine with an appropriate isothiocyanate using techniques known in the art. The methods according to the invention can be part of a global water treatment regime. Thiourea can be used with other chemicals for water treatments particularly with biocides (for example, algicides, fungicides, bactericides, molluscicides, oxidants, etc.), stain removers, lighteners, flocculants, coagulants or other chemicals commonly used in the treatment. water treatment. For example, submergible surfaces can be contacted with a thiourea as a pre-treatment to inhibit adhesion bacterial and placed in the aqueous system using an icrobicide to control the growth of microorganisms, by, an aqueous system that undergoes heavy biological fouling can first be treated with an appropriate biocide to overcome the existing fouling. A thiourea can then be used to maintain the aqueous system. Alternatively, a thiourea in combination with a biocide can be used to inhibit bacteria from adhering to submerged surfaces within the aqueous system while the biocide acts to control the growth of microorganisms in the aqueous system. Such a combination generally allows less microbiocides to be used. "Growth control of microorganisms" in an aqueous system means controlling, at, or below a desired level and during a desired period for the particular system. This can eliminate microorganisms or prevent their growth in aqueous systems. Thiourea can be used in the methods of the invention as a solid or liquid formulation. Accordingly, the present invention also relates to a composition containing a thiourea. The composition comprises at least one thiourea in an amount effective to inhibit bacteria from adhering to a submergible surface or a submerged surface within a system aqueous. When used in combination with another water treatment chemical such as a biocide, the composition may also contain this chemical. If formulated together, the thiourea and the water treatment chemical should not be subjected to adverse reactions that could reduce or eliminate their efficiency in the aqueous system. Separate formulations are preferred where adverse interactions may occur. Depending on its use, a composition according to the present invention can be prepared in various ways known in the art. For example, the composition can be prepared in liquid form as a solution, dispersion, emulsion, suspension or paste; a dispersion, suspension or paste in a non-solvent, - or as a solution by dissolving the thiourea in a solvent or combinations of solvents. Suitable solvents include, but are not limited to, ketones, glycols, alcohols, ethers or other water dispersible solvents. Aqueous formulations are preferred. The composition can be prepared as a liquid concentrate for dilution before its intended use. Common additives such as surfactants, emulsifiers, dispersants and the like can be used as is known in the art in order to increase the solubility of thiourea or other components in a composition or system of liquids such as a composition or aqueous system. In many cases, the composition of the invention can be solubilized by simple agitation. Dyes or fragrances can also be added for appropriate applications such as bath water. A composition of the present invention can also be prepared in solid form. For example, thiourea can be formulated as a powder or tablet using means known in the art. The tablets may contain a variety of excipient known in the art of tabletting such as colorants or other coloring agents and perfumes or fragrances. Other components known in the art such as fillers may also be included, binders, glidants, lubricants or antiadherents. These latter components can be included to improve the properties of the tablets and / or the tabletting process. The following illustrative examples are given to describe the nature of the invention more clearly. However, it should be understood that the invention is not limited to the specific conditions or details set forth in the examples. EXAMPLE: Example 1: Combinatorial Preparation of Thiourea Compounds A single-neck round bottom flask of 100 ml was charged with the following amines: 0.62 g of dicyclohexylamine, 0.78 g of dioctylamine, 0.34 g of hexamethyl ina, 0.34 g of 3-methylpiperidine, 0.34 g of 2-methylpiperidine. , 0.30 g of morpholine, 0.43 g of 3,5-dimethylpiperidine, and 0.35 g of dipropylamine. This mixture was added enough methanol to dilute the mixture to 40 ml. Five grams of 4-nitrophenyl isothiocyanate were dissolved in 10 ml of methanol, then added in one portion. A reflux condenser was then connected to the flask and the mixture was heated to reflux for 4 hours. After that time, the flask was allowed to cool to room temperature, the excess solvent was removed under vacuum, to give a bright red liquid, which then gelled to a dark red semi-solid. Example 2: Test for Bacterial Adhesion Test Method: The following method effectively defines the ability of a chemical compound to inhibit bacterial reaction or attack the formation of existing bound microorganisms, on various types of surfaces. As a general review, bioreactors were constructed in which glass plates of approximately 2.54 cm x 7.62 (1 inch x 3 inches) were attached to the edge of the bioreactor. The lower ends (approximately 5.08 cm (2 inches)) of the plates were immersed in a growth medium bacterial (pH 7) inside the bioreactor that contained a known concentration of the test chemical. After inoculation with known bacterial species, the test solutions were stirred continuously for 3 days. Unless indicated otherwise in the following results, the medium within the bioreactor became turbid at the end of the three days. This turbidity indicated that the bacteria will proliferate in the medium despite the presence of the tested chemical. This also shows that the chemical, the tested concentration, substantially did not show biocidal (bactericidal) activity. A staining procedure was then formed on the plates in order to determine the amount of the bacteria bound to the surfaces of the plates. Construction of bioreactors: The bioreactors comprised a 400 ml glass agitator on which a layer was placed (covered with a glass petri dish of 9 cm in normal diameter) With the lid removed, the plates of the material of choice were tapered At one end with adhesion tape and were suspended inside the bioreactor from the "top edge of the agitator.This allows the plates to be immersed within the test medium.Officially, four plates (replicated) were uniformly separated around the bioreactor. presented below are the average of the four replicates. A magnetic stirring rod was placed in the lower part of the unit. placed the lid, and put the bioreactor in the autoclave. Glass plates were used as examples of hydrophilic surfaces. Bacterial Growth Medium: The liquid medium used in bioreactors was previously described by Delaquis, et al., "Detachment of Pseudomonas Fronfluorescens from Biofilms on Glass Surfaces in Response to Nutrient Stress," Microbial Ecology 18: 199-210, 1989. composition of the medium was:, Glucose 1.0 g K2HP04 5.2 g KH2P04 2.7 g NaCl 2.0 g NH4C1 1.0 g MgSO4. 7H20 0.12 g Trace element 1.0 ml deionized H20 l.O 1 Trace element solution: CaCl2 1.5 g FeS04. 7H20 l.O g MnS04. 2H20 0.35 g NaMn04 0.5 g Deionized H20 1.0 1 The medium was autoclaved and then allowed to cool. If a sediment formed in the medium treated by autoclave, the medium was resuspended by shaking before use. Preparation of Bacterial Inocula: The Bacillus, Flavobacterium, and Pseudomonas genus bacteria were isolated from a lama deposit of a paper mill and kept in continuous culture. The test organisms were collided separately on agar for plate control and incubated at 30 ° C for 24 hours. With a sterile cotton swab, portions of the colonies were removed and suspended in sterile water. The suspensions were mixed very well and adjusted to an optical density of 0.858 (Bacillus) 0.625 (Flavobacterium), and 0.775 (Pseudomonas) at 686 nm. Proof of Production of Biofilm / Ouimics: To four bioreactors separately was added 200 ml of the medium prepared previously. The chemicals to be tested were first prepared as a stock solution (40 mg / 2 ml) using water or a mixture of acetone: methanol at 9: 1. (ac / MeOH) as a solvent. An aliquot of 1.0 ml of the stock solution was added to the bioreactor using moderate continuous magnetic stirring. This provided an initial concentration of 100 ppm for the test compound. A bioreactor (Control) does not contain test compound. Aliquots (0.5 ml) of each of the three bacterial suspensions in each bioreactor were then introduced. The bioreactors were then provided with shaking It continues for three days to allow an increase in the bacterial population and the deposit of cells on the surfaces of the plates. Evaluation of Results: Preferred thiourea compounds a-h were evaluated using the above procedure. After the test, the plates were removed from the bioreactors and placed vertically to allow drying with air. The degree of adhesion of bacteria to the test surface was then calculated using a staining procedure. The plates were briefly flamed in order to fix the cells to the surface and then transferred for two minutes to a Gram Crystal Violet vessel (DIFCO Laboratories, Detroit, MI). The plates were rinsed gently under running water, and then carefully rinsed. The group of adhesion of microorganisms (Bacterial adhesion) was then determined by visual examination and subjective labeling of each plate. The intensity of the stain is directly proportional to the amount of bacterial adhesion. The following biofilm classifications are given: 0 = essentially none 3 = moderate 1 = scarce 4 = heavy 2 = light Chemical treatments were evaluated in relation to the control which normally receives a classification average for the four bioreactor plates in the 3-4 scale. Compounds that receive an average rating on the 0.2 scale were considered effective to prevent adhesion of bacteria to submerged plates. The results are shown in the following table.

Minimum Inhibitory Concentration (MIC) against bacteria E.

Aerogenes determined with an 18-hour ealee baeal test both pH 6 and pH 8. 2 Combination experiment of all compounds (a) - (h). While the particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited to those embodiments. Other modifications can be made. The appended claims are intended to cover any such modification, since they fall within the spirit and true scope of the invention.

Claims (14)

1. CLAIMS 1. A method for inhibiting the adhesion of bacteria to a submergible surface comprising the step of contacting the submergible surface with a thiourea in an amount effective to inhibit bacteria from adhering to a submergible surface, characterized in that the thiourea is a compound of the formula: wherein: R1 and R2 are each independently an alkyl group of C? -C ^ 4 or R1 and R2 together with the nitrogen atom carrying them form a 5-8 membered heterocyclic ring of the formula:
2. X is O, NH, O CH2; R5 is methyl, hydroxymethyl, hydroxyethyl, or halo; n varies from 0 to 3; R3 is an alkyl group of CÍ-C7; and R4 is hydrogen. 2. The method according to claim 1, characterized in that R1 and R2 are a C3-C10 alkyl group together with the nitrogen atom carrying them is a heterocyclic ring selected from piperidinyl, methylpiperidinyl, dimethylpiperidinyl, hydroxymethylpiperidinyl, dichloropiperidinyl , hexamethyleneiminyl, and morpholinyl; R3 is a C3-C5 alkyl group; and R5 is hydrogen.
3. 3. The method according to claim 1, characterized in that the thiourea is selected from: n-butyl-N ', N' -dicyclohexylthiourea, n-butyl-N ', N' -dioctylthiourea, n-butyl-N '- hexamethyleneiminothiourea, n-butyl-N'-3-methylpiperidinothiourea, n-butyl-N'-2-methylpiperidiniothiourea, n-butyl-N'-morpholinothiourea, n-butyl-N'-3,5-dimethylpiperidiotiourea, n-butyl -N ', N' -dipropylthiourea, and mixtures thereof, and wherein a submergible surface is a ship's hull, a boat hull, a marine structure, a tooth surface, a medical implant surface, or a surface of an aqueous system.
4. 4. The method for controlling the biofouling of an aqueous system, characterized in that it comprises the step of adding to the aqueous system a thiourea in an amount effective to inhibit the adhesion of bacteria to a submerged surface within the aqueous system, wherein the thiourea is a compound of the formula: wherein: R1 and R2 are each independently an alkyl group of C? -C] _4 or R1 and R2 together with the nitrogen atom carrying them form a 5-8 membered heterocyclic ring of the formula:
5. X is O, NH, or CH2; R5 is methyl, hydroxymethyl, hydroxyethyl, or halo, - n varies from 0 to 3; R3 is a C1-C7 alkyl group; and R4 is hydrogen. 5. The method according to claim 4, characterized in that the urea is selected from: n-butyl-N ', N' -dicyclohexylthiourea, n-butyl-N ', N' -dioctylthiourea, n-butyl-N '- hexamethyleneiminothiourea, n-butyl-N'-3-methylpiperidinothiourea, n-butyl-N'-2-methylpiperidiniothiourea, n-butyl-N 1 -morpholinothiourea. n-butyl-N '-3,5-dimethylpiperidiotiourea, n-butyl-N', N '-dipropylthiourea, and mixtures thereof, and wherein the effective amount of the thiourea ranges from 10 ppm to 500 ppm.
6. 6. The method according to claim 4, characterized in that the addition step comprises adding sufficient thiourea to the aqueous system to reduce any biofouling existing in the aqueous system.
7. 7. The method of compliance with the claim 4, characterized in that the aqueous system is an industrial water system selected from a cooling water system, a fluid system for working metals, a water system for forming paper, and a water system for textile manufacturing.
8. 8. The method according to claim 4, characterized in that the aqueous system is a recreational water system selected from a pool, a fountain, an ornamental pool, an ornamental pool and an ornamental stream. The method according to claim 4, characterized in that the aqueous system is a sanitation water system selected from a water system, a system for water treatment and a drainage treatment system. The method according to claim 4, characterized in that it comprises the step of adding an effective amount of a biocide to the aqueous system to control the growth of a microorganism in the aqueous system. 11. The method according to claim 10, characterized in that such an aqueous system is selected from an industrial water system, a recreational water system and a sanitization water system. 12. A composition for controlling the biofouling of an aqueous system, characterized in that it comprises at least one thiourea in an amount effective to inhibit the adhesion of bacteria to a submergible surface or submerged surface within the aqueous system, wherein the thiourea is a compound of the formula: wherein: R1 and R2 are each independently a C1-C alkyl group? or R1 and R2 together with the nitrogen atom carrying them form a 5-8 membered heterocyclic ring of the formula: X is O, NH, O CH2; R5 is methyl, hydroxymethyl, hydroxyethyl, or halo, - n ranges from 0 to 3; R3 is a C1-C7 alkyl group; and R4 is hydrogen. The composition according to claim 12, characterized in that the thiourea is selected from: n-butyl-N ', N' -dicyclohexylthiourea, n-butyl-N ', N' -dioctylthiourea, n-butyl-N '-hexamethyleneiminothiourea, n-butyl-N'-3-me-ilpiperidinothiourea, n-butyl-N'-2-methylpiperidiniothiourea, n-butyl-N 1 -morpholinothiourea, n-butyl-N'-3, 5 -dimethylpiperidiotiourea, n-butyl-N *, N '-dipropylthiourea, and mixtures thereof. The composition according to claim 12, characterized in that it further comprises a biocide in an amount effective to control the growth of a microorganism in the aqueous system.