Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Reexamination Certificate
2001-12-05
2004-06-15
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
C210S752000, C210S755000, C210S764000, C422S003000, C422S037000
Reexamination Certificate
active
06749758
ABSTRACT:
TECHNICAL FIELD
This invention relates to, and has among its objectives, biocidal treatment of water bodies so that stable response of an oxidation-reduction potential sensor is provided.
REFERENCE TO COMMONLY-OWNED APPLICATIONS
Commonly-owned application Ser. No. 09/323,348, filed Jun. 1, 1999, now U.S. Pat. No. 6,303,038 B1, issued Oct. 16, 2001, describes solid mixtures of dialkylhydantoins and bromide ion sources for water sanitation. Commonly-owned copending application Ser. No. 09/484,844, filed Jan. 18, 2000, describes chemical processes from which compositions of the present invention can be formed or derived. Commonly-owned application Ser. No. 09/484,687, filed Jan. 18, 2000, now U.S. Pat. No. 6,508,954 B1, issued Jan. 21, 2003, describes 1,3-dibromo-5,5-dimethylhydantoin particulate solids producible by the processes of Application Ser. No. 09/484,844, such solids having unprecedented enhanced properties, and compacted articles made from such particulate solids without use of a binder. Commonly-owned application Ser. No. 09/483,896, filed Jan. 18, 2000, now U.S. Pat. No. 6,448,410 B1, issued Sep. 10, 2002, relates to the granulation of small average particle size 1,3-dibromo-5,5-dimethylhydantoin and also to the compaction of such granulated products to form larger-sized articles. Commonly-owned application Ser. No. 09/484,891, filed Jan. 18, 2000, now U.S. Pat. No. 6,495,698 B1, issued Jan. 17, 2003, relates to the compacting of 1,3-dihalo-5,5-dimethylhydantoins other than 1,3-dibromo-5,5-dimethylhydantoin without use of binders, and to the novel compacted forms so produced. Commonly-owned application Ser. No. 09/484,938, filed Jan. 18, 2000, now U.S. Pat. No. 6,565,868 B1, issued May 20, 2003, describes using 1,3-dibromo-5,5-dimethylhydantoin for microbiological or biofilm control in water. Commonly-owned copending application Ser. No. 09/487,816, filed Jan. 18, 2000, relates in part to converting 1,3-dihalo-5,5-dimethylhydantoins into compacted articles using novel binders. Commonly-owned copending application Ser. No. 09/775,516, filed Feb. 2, 2001, describes microbiological control in aqueous media achieved by introducing a microbiocidally effective quantity of one or more 1,3-dibromo-5,5-dialkylhydantoins into the aqueous medium. Commonly-owned copending application Ser. No. 09/778,228, filed Feb. 2, 2001, describes biocidally-active 1,3-dibromo-5,5-dialkylhydantoin biocidal compositions in readily identifiable forms. Commonly-owned copending application Ser. No. 09/893,581, filed Jun. 28, 2001, describes microbiological control in poultry processing using a halogen-based microbiocide or 1,3-dihalo-5,5-alkylhydantoin.
BACKGROUND
It is the goal of any owner or operator of recreational water bodies, swimming pools, spas, hot tubs or the like to provide pool water which is maintained so that there are no detrimental microorganisms. To this end, the pool owner or operator may choose from a wide variety of biocidal chemical systems to ensure that a biocidally effective amount of water-treating agents is present in the water body on a continuous basis.
The more commonly used biocidal agents are halogen-containing biocides. As referred to herein, halogen or halo- refers to either chlorine or bromine. These agents register as “free chlorine” or “available chlorine” species in commonly used testing procedures. Persons using biocidal agents in the biocidal treatment of water customarily, if not universally, refer to “free chlorine” level as a measure of biocidal control, even though the agent may contain bromine as the oxidizing species. The EPA has determined that a level of 1.0-1.5 ppm of available chlorine should be maintained at all times to continuously kill the microorganisms and algae in such water systems. The active bromine level may be expressed as free chlorine for ease of comparison to industry standards. For example, the biocide, 1,3-dibromo-5,5-dimethylhydantoin, hydrolyzes into 2 molecules of HOBr, which registers as “free chlorine” species in commonly-used standard test procedures for determining the quantity of halogen-containing microbiocidal agent to be used for water treatment. To convert such chlorine values to active bromine values, the chlorine value should be multiplied by 2.25. Thus, in bromine-containing systems sanitation is maintained when the active bromine, as Br
2
, is 2.0 to 3.0 ppmw.
Among the available techniques for indicating the concentration of biocidal agent present in the water system, two are used most often. In the more preferred system, an electronic Oxidation-Reduction Potential (ORP) sensor, linked to a controller device, is a sophisticated and labor efficient tool for indicating a level of halogen present which is consistent with satisfactory sanitation quality. Therefore, many commercial pool operators and some private pool owners possess ORP (Oxidation-Reduction Potential) monitoring probes interfaced to a controller. The controller electronically actuates a valve to control a flow of water to a chemical feeding device or activates a delivery pump for delivery of a biocidal chemical to the water system. When a sensing electrode of either platinum or gold, comes in contact with a solution containing species for which the probe is sensitive, an electrical potential develops at the electrode's surface. The magnitude of the potential relates to the concentration of the species being measured, so that the higher the potential, the higher the species concentration. In a recreational pool situation, the species present which presents a variation in concentration causing a change in potential is the active species of the biocidal chemical, such as active bromine. The ORP reading may be equated to the concentration of the active bromine and reported as a “free chlorine” value as per the industry naming convention. The ORP probe is pre-set to a particular mV range and will signal the controller when the mV condition deviates outside this range necessitating addition of the appropriate biocidal chemical. When sufficient amount of biocidal chemical has been delivered to the water such that the pre-set ORP condition is attained, the controller de-activates the switch to the feeding device so that no more biocidal chemical is released into the water.
The use of an ORP sensor allows the pool operator to measure the potential generated by the active form of the biocidal chemical. Additionally, ORP monitoring has an advantage in that it is an ongoing electronic process requiring no test chemicals or agents after initial stabilization. Monitoring of sanitation levels is constantly performed as opposed to being performed on some predetermined schedule basis.
Another method of water management and treatment is use of the DPD test kit which utilizes a chemical reaction between a water sample, N,N′-diethyldiphenylenediamine (DPD) and a buffer to cause a color change which can be visibly compared to a color chart of halogen concentrations. The use of a DPD test kit by a pool operator or pool technician requires the operator to sample the water, add appropriate reagent(s) and visually compare the color change of the pool water sample against a color standard chart to arrive at an approximation of the active chlorine or bromine value. If the operator employs the DPD test as the sole monitoring method, the operator, after testing, must take steps to add an appropriate biocidally effective amount of the treatment agent to the water. Thus this method tends to require more time and effort than the ORP method.
Typically, the operator will employ the DPD test kit procedure as a check on the ORP sensor reading during the initial stabilization time interval of the ORP sensor reading in a water facility which has been drained and re-filled or in which the biocidal agent is being changed.
When the pool ORP monitoring system is initially started up, either with untreated water or with water in which the biocidal agent of choice is to be changed, e.g. from a chlorine-containing system to a bromine-containing system, the pool operator may observe a
Howarth Jonathan N.
Sanders Michael J.
Albemarle Corporation
Hruskoci Peter A.
Spielman, Jr. Edger E.
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