Stabilized and activated bromine solutions as a biocide and as an antifouling agent

Abstract

The invention provides a process of removing or preventing biofouling, particularly on surfaces of industrial and agricultural equipment in contact with aqueous liquids. The process employs an antifouling composition of stabilized active halogen having a low pH.

1 . A process of removing or preventing biofouling in a volume of an aqueous liquid or on a surface in contact with an aqueous liquid, comprising
 i) providing an aqueous composition (stock antifouling solution) containing urea and an active halogen source, wherein the molar ratio urea/halogen is at least 1/1, and the pH of said aqueous composition is acidic; and   ii) contacting said volume or said surface with said composition obtained in step i);   wherein said active halogen source is selected from Cl 2 , DC-DMH, DC-MEH, TCCA, Na-DCC, and a mixture of an oxidizer with a bromide source selected from HBr and a bromide.   
     
     
         2 . A process according to  claim 1 , further comprising a step of diluting said stock antifouling solution with water, thereby obtaining a working antifouling solution, and contacting said volume or said surface with said working solution rather than said stock solution. 
     
     
         3 . A process according to  claim 1 , wherein said urea reacts with said halogen source to provide chlorourea in said stock solution. 
     
     
         4 . A process according to  claim 1 , wherein said oxidizer is chlorourea, and wherein said chlorourea reacts with said bromide source and urea to provide a mixture of chlorourea and bromourea in said stock solution. 
     
     
         5 . A process according to  claim 1 , wherein said active halogen source is a bromide source with an oxidizer, and wherein said oxidizer is aqueous chlorourea. 
     
     
         6 . A process according to  claim 1 , wherein said active halogen source is a bromide source with an oxidizer, and wherein said oxidizer is solid chlorourea. 
     
     
         7 . A process according to  claim 1 , wherein the molar ratio of urea/halogen is at least 2/1, and the pH value of said aqueous composition is less than 4. 
     
     
         8 . A process according to  claim 1 , comprising
 mixing water, urea, and said active chlorine source, wherein the molar ratio urea/total chlorine is greater than about 4/1, thereby obtaining an aqueous composition of stabilized chlorourea.   
     
     
         9 . A process according to  claim 1 , comprising
 i) mixing water, urea, and said chlorine source, wherein the molar ratio urea/total chlorine is greater than about 4/1, thereby obtaining an aqueous composition of stabilized chlorourea;   ii) optionally admixing a bromide source selected from a bromide and HBr to said chlorourea of step i), thereby obtaining an aqueous composition of stabilized active bromine;   iii) optionally diluting said composition obtained in step ii) with water, thereby obtaining a working solution; and   iv) contacting said volume or said surface with said composition obtained in step ii) or with said working solution of step iii).   
     
     
         10 . A process according to  claim 9 , wherein said step ii) is performed after a prolonged period of storage of said aqueous composition of stabilized active chlorine, and at an appropriate time before said step iv). 
     
     
         11 . A process according to  claim 10 , wherein said period of storage is up to two years, and said appropriate time is up to one year. 
     
     
         12 . A process according to  claim 9 , comprising mixing water, urea, and chlorine. 
     
     
         13 . A process according to  claim 9 , wherein the molar ratio urea/bromine is up to 40/1, and wherein said bromide source is selected from the group consisting of NaBr, KBr, and HBr. 
     
     
         14 . A process according to  claim 1 , wherein said stock solution comprises halogen in a concentration of 0.1-20 wt %, and wherein said stock solution is stable on prolonged storage of up to one year. 
     
     
         15 . A process according to  claim 9 , wherein said aqueous composition of stabilized active chlorine has a concentration of up to 10 wt %, and wherein said bromide or HBr in said step ii) are added in an amount corresponding to a molar ratio of Br/Cl of from 0.1 to 2.0. 
     
     
         16 . A process according to  claim 2 , wherein said working solution exhibits biocidal activity when diluted down to an active halogen concentration corresponding to 0.1 ppm as active chlorine. 
     
     
         17 . A process according to  claim 1 , for treating water with high TOC content. 
     
     
         18 . A process according to  claim 1 , wherein said surface comprises irrigation pipes, waste water, industrial cooling water, process water, and equipment in the Pulp & Paper industry. 
     
     
         19 . A process according to  claim 1 , wherein said aqueous composition unclogs pierced irrigation pipes and fertilizes the irrigated plot. 
     
     
         20 . A process according to  claim 1 , wherein said aqueous composition further contains salts with additional fertilizing and/or stabilizing properties. 
     
     
         21 . A process according to  claim 1 , wherein said step of providing the aqueous composition is a batch procedure. 
     
     
         22 . A process according to  claim 1 , wherein said step of providing the aqueous composition is a continuous procedure. 
     
     
         23 . A process of preparing an antifouling or disinfecting composition comprising water, urea, and active halogen, comprising
 i) preparing an aqueous solution of urea;   ii) adding to said solution obtained in step i) an active chlorine source selected from the group consisting of Cl 2 , TCCA, Na-DCC, DC-DMH, and DC-MEH, at a temperature of between 0° C. and 25° C., while stirring,   wherein the molar ratio urea/chlorine is greater than about 1/1, thereby obtaining an aqueous composition of stabilized chlorourea; and optionally   iii) admixing to said stabilized chlorourea a bromide source to an amount corresponding to a molar ratio Br/Cl of from 0.5 to 2.0, at a temperature of between 0° C. and 25° C.;   wherein a time period between said steps ii) and iii) is up to two years.   
     
     
         24 . A process according to  claim 23 , wherein said urea, said active chlorine source, and optionally said bromide source are provided as aqueous streams which are optionally diluted with water before combining and forming said antifouling or disinfecting composition. 
     
     
         25 . A process according to  claim 23 , further comprising a step of adding to the mixture obtained in step ii) or step iii) salts with fertilizing and stabilizing properties. 
     
     
         26 . An antifouling or disinfecting stock solution comprising
 i) urea having a concentration of from 2 wt % to 45 wt %; and   ii) an active chlorine source selected from the group consisting of Cl 2 , TCCA, Na-DCC, and halogenated alkylhydantoin selected from DC-DMH, DC-MEH, where the total chlorine amount is from 0.1 wt % to 5 wt %.