BACKGROUND [0002] Clean system surfaces are critical to the efficient operation and maintenance of heat rejection devices such as recirculating cooling systems. The art and science of water treatment focuses onthe economical control of scales, deposits, corrosion products, and microorganisms throughout the cooling system. The build-up of these surface contaminants can give rise to an avalanche of problems-poor heat transfer, high energy consumption, filmfillpluggage, increased maintenance expenditures, short system life, high overall operating costs, etc.

[0003] Microorganisms attachedto surfaces, commonlyknown as biofilms, contribute to many ofthese problems. Some ofthe problems posedbybiofilms inindustlialwater systems include the following: A) Biofilm deposits are effective thermal insulators. One prior study found the thermal conductivity of a biofilm to be 25% that of a calcium carbonate scale of equivalent thickness. This results in decreased heat transfer and increased energy consumption.

B) Biofilmdeposits areacriticalfactorinflmllfouling. Highefficiencyfilmfills, whichare prone to fouling, were introduced in the 1970's and 1980's. In one prior study, the combinationofbiofouling andsiltledto an"astounding"weightgainof 14. 8 lbs/cuft offHm fillin42 days. Silt-onlytreatmentprovided littleweight gain (2. 3 lb/cu ft) withinthe same time frame. The authors ofthat study concluded that"silt alone does not appear capable of [film fill] failure plugging." C) Biofilm deposits increase corrosion of metallurgy. The colonization of surfaces by microorganisms andtheproducts associatedwithmicrobialmetabolicprocesses create environments that differ greatly from the bulk solution. Low oxygen environments at the biofilm/substrate surface, for example, provide conditions where highly destructive anaerobic organisms such as sulfate reducing bacteria can thrive. This leads to MIC (microbiallyinducedconosion), aparticularlyinsidiousformofcomosionwhich, according to onepublishedreport, canresultinlocalized, pittingconosionrates 1000-foldhigherthan that experienced for the rest ofthe system. In extreme cases, NUC leads to perforations, equipment failure, and expensive reconditioning operations within a short period oftime.

For example, it has been indicated that in a newly-build university library without an effective rnicrobiologicalcontrolprograin, sections ofthe cooling systempipeworkhadto bereplacedafterjustoneyearofservice dueto accumulations ofsludge, slime, andSRBs.

D) Perhaps the greatest problem associated with biofilms is health related. Itisknownthat biofihns can create an environment for Legionella ps2eumophila, the bacterium species responsible for Legionnaires'disease, to thrive. This bacteriumhas been reported to be capable of attaining highrisklevels inman-madewater systems such as cooling towers and evaporative condensers, whirlpool spas andbaths, domestic hot water/shower systems, and grocerymisters. Deadly outbreaks ofLegionnaires'disease continue to takeplacewith regularity despite a growing list of published guidelines and recommended practices by AWT, CTI and other industry groups and governmental agencies. For example, inApril, 2000 a large outbreak occurredinAustraliain anew facilitythatwas commissionedjust 3 1/2 months before. This outbreakhas beenreportedto haveresultedin 101 confirmed cases of Legionnaire's disease and 2 deaths.

[0004] Bio films are clearly the direct cause or potentiators for many cooling system problems.

Several years ago, the economic impact of bio films in the US alone was estimated at $60 billion dollars. <BR> <BR> <BR> <BR> <BR> <P>[0005] Biofilms are a collection of microorganisms attachedto asurface, themetabolicproducts they produce, and associated entrained debris (silt, scale, iron, etc. ).

[0006] Initial colonization of a surface takes place when an organism present in the bulk water such as Pseudomonas aeruginosa--a common slime-fomning bacteria in industrialwater systems --adheres to a surface. This changeinstate fromfiee-swinlming/planktonic stateto attached/sessile <BR> <BR> <BR> <BR> state causes adramatictransformationinthemicroorganism. Genes associatedwiththeplanktonic state turn off; genes associated with the sessile state turn on. Typicallythe microorganismloses appendages associated with the free swimming state, such as flagella, and obtains appendages more appropriate for the present situation, such as short, hair-like pilleawhich afford numerous points for attachment. The attachment process further stimulates production of slimy, polysaccharide (starch-like) materials generally termed extracellular polymeric substances (EPS). Givenproper conditions, more bacteria attach to the surface. Eventually the surface is covered with a layer of attached bacteria and associated EPS.

[0007] If this was all that takes place, biofilms might be relatively easy to control. However, bacteria continue to colonize the surface building up to several and evenhundreds of cell layers thick. Recent scientific evidence indicates that this colonization process proceeds with ahigh degree of order. Cells withinthe developing microcolony communicate with one another using a signaling mechanism termed quorum sensing. The individual cells constantly produce small amounts of chemical signals. When these signals reach a certain concentration, they modifythe behavior of the cells and result, for example, in the creation of water channels. The water channels enable the transport of nutrients into the colony and the removal of waste products from the colony.

[0008] Soonothermicroorganisms findniches withinthemicrocolonysuitable forgrowth. Low oxygen or anaerobic conditions at the substrate/microcolony surface prove inviting for destructive microorganisms such as sulfate-reducing bacteria (SRBs). Protozoa and other amoebae welcome <BR> <BR> <BR> <BR> the opportunityto graze onthesessilebacterialcommunity. Legionellapneumophila and/or other<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> pathogenic organisms findsuitableniches to reproduce andthrive. The fullydevelopedmicrocolony thus contains a variety of chemical gradients and consists of a consortia of microorganisms of differing types and metabolic states.

[0009] Eventually conditions within the microcolony may not be ideal for some or all of the microorganisms present. The microorganisms detach, enter the bulk water, and search for other colonization sites. It has been recently been discovered that, as in the case for creation of water channels withinthe developingbiofilm certainchemicalsignals governthe detachmentprocess as well.

[0010] The microorganisms present in the biofilmtypically exhibit reduced susceptibility to biocides. Inotherwords, once established, biofilms canbepersistentanddifficulttogetridof. This is due to a number of factors: 1) ReducedPenetration. Biofilmsusedtobeviewedasofferinganimpenetrablebarrierby virtue ofthe layer of EPS surrounding the attached organisms. This view has since been modified slightlywith the discovery ofwater channels-in effect aprimitive circulatory system--throughout the biofilm. The current view is that althoughmany substances such as chloride ion, for example, enjoy ready access into the interior of the biofilm, reactive substances suchas chlorineorotheroxidizingbiocides canbedeactivatedviareactionwith EPS atthebiofilmsurface. For example, apaper onstudies of7-daybiofilms challenged with 5 ppm chlorine indicates that chlorine levels were only 20% that ofthe bulkwater in thebiofilminterior. Organismswithinthe biofilmare thus exposed to reduced amounts of biocide.

2) Intrinsic Resistance. Biofilm organisms exhibit vastly different characteristic than their planktonic counterparts. For example, apaperpublishedin 1997 shows that even one-day bio films indicate amuch-reduced susceptibility to antibiotics relative to theirplanktonic counterparts--often requiring a 1000-fold increase in antibiotic dose for complete deactivation of the biofilm.

3) Microbiological Diversity. Biofilms offer many different microniches--oxygenlich areas, oxygen depleted areas, areas of relatively high pH, areas of low pH, etc. These wide-ranging environments lead to diversity in types of organisms andmetabolic activity.

Cells nearthe bulkwater/biofilmsurface, for example, respire and are reported to grow at agreaterrate thanthosewithinthe interior ofthe biofilmwhichmaybe essentially dormant.

These dormant cells are less susceptible to biocide treatment and can repopulate the biofilm rapidly when conditions are favorable.

[0011] Factors that promote biofilm development include the following: a) Substrate and Temperature.

[0012] Although not often under the control of the water treater, substrate and temperature can <BR> <BR> <BR> dramaticallyimpactbiofilmdevelopment. Apaperpublishedin 1994reports onstudies onthe effect<BR> <BR> <BR> <BR> <BR> ofsubstrate andtemperature oncolonizationbybiofilmbacteriaandbiofilin-associatedLegione lla over aperiod of 1-21 days. Colonizationprovedgreatest onplastic surfaces (cPVC, polybutylene) <BR> <BR> <BR> compared to copper at all temperatures. Colonization was consistently high on the plastic surfaces at all temperatures except 60°C where counts dropped off by 1-2 log units. Legionella counts were greatest on all surfaces at 40°C with no Legionella detected at 60°C. L. pneumophila represented a low percentage ofthemicrobialpopulation ofthe plastic surfaces at 20°C (0. 1%) but this increased greatly (10-20%) at 40°C. Interestingly, copper inhibited colonization by L. p72eumophila as this organism was only detected at 40°C where it represented 2% of the total bacterial population.

[0013] In another study, 48-hour biofilms were grown on galvanized iron, glass, and PVC.

Biofilm counts on the plastic surface (-10 CPUs/cm) were about 1 log count higher than on the other surfaces. The action of certain oxidizing biocides, viz. , chlorine, bromine, and N, N'- bromochloro-5, 5-dimethylhydantoin (BCDMH) provedto be greatest on galvanized iron and least on PVC. The authors concluded that"PVC surfaces are problematic by supporting biofilm colonization, disinfection resistance, and regrowth." [0014] In another study, populations of 21-day oldbiofilms were about 1 log greater when grown on mild steel (5.5 to 6.8 log CFU/cm2) than stainless steel (4.7 to 5. 8 CPU/cm. Dosages of BCDMH (1 mg/Lfieeresidual) reducedbiofilmcounts by 1.4 logs on mild steel and 2. 0 logs on <BR> <BR> <BR> stainless steel at 30°C. Legionellapne2xmophila represented 1-10% ofthe totalpopulation ofthe biofilms. However, no viable Legionella were recovered fi-omthe biofilms on either metal surface upon exposure to biocide (1 mg/L BCDMH) for 24 hours.

[0015] Results of studies in a model cooling tower on the effect of temperature (30-40'C) on biofilmbactelia, biofilmprotein, andbiofilmcarbohydrate on stainless steel surfaces has been reported. Analysis after 14 days showedthat controlpopulations ofbiofilinbacteriawere greatest at40°C andthatthe amountofbiofilmproteinandcarbohydrateproducedwere greatest at 35°C.

The largest portion ofthe biomass on aweightbasis was carbohydrate and this represented about 4 times that of protein. The relatively high amount of carbohydrate (representative of EPS) indicates the extentto whichbiofilmbacteria canproduce slime in cooling systems. Biocide studies under highnutrient conditions using 3 ppmisothiazolone (3 ppma. i., dosed 3 xper week) indicated good control of heat transfer resistance and biofilm carbohydrate. However, viable cell counts withthe biocide were equivalent to that of control.

[0016] The preceding studies indicate that colonizationbybiofilmbacteria is generally greatest on plastic surfaces and least on copper surfaces. Colonization ofmild steel and stainless steel appears to be an intermediate case with stainless steel less colonized than mild steel. The optimum temperature for colonizationbybiofilmbacteria andbiofilm-associatedLegionella appears to lie inthe range of 30-40°C. At these temperatures Legionella can colonize plastic and steel surfaces in numbers representing up to 20% ofthe totalmicrobialpopulation anproductionofbiofilmslime is at its peak. These studies support problems associatedwith fouling of film fills which are typically made of plastic such as PVC. They also suggest that systems containing substantial amounts of copper pipework may be less prone to biofilm-related problems. b) Flow Rate and Temperature [0017] The impact ofperacetic acid/hydrogenperoxide onbiofilms grownon304 stainless steel disks was reported in 1998. Biofilms grown under flow conditions were 3 times more sensitive to the biocide than those grown statically (concentration for 2 log kill-25 ppm (flow) ; 80 ppm (static)). <BR> <BR> <BR> <BR> <P>Decreasedbiocide efficacyunderstatic conditionswas explainedbyoccurrence of stagnationand starvationeffectsinthebiofilm (microbiologicaldiversity) andproductionofmorecopious amounts of extracellular polymer (reduced biocide penetration).

[0018] High flow rates dramatically boosted biocide activity. Up to a six-log increase in <BR> <BR> <BR> <BR> disinfectionwas obtainedunderturbulentflowvs. static conditions. This increasewas attributedto improved mass transport of disinfectant into biofilm cells (increased biocide penetration). <BR> <BR> <BR> <P>Temperatureincreasedbiocide activity as well. Efficacyjumpedmorethan3-logs ingoing fiom20 to 50°C.

[0019] In another study, an increase inflow rate improved biofilm removal on 3-day biofilms treated with 50 ppm glutaraldehyde. Interestingly, the authors point out that low levels of glutaraldehyde had little effect on biofilm removal with a"no effect"level of 20 ppm. This was thoughtto be due to crosslinking ofthe glutaraldehydewiththe outer surface ofthe cells effectively preventing penetration into the biofilm.

[0020] These studies indicate that biofilms grown under static or low flow conditions can be inherently more difficult to control. Such low flow, stagnant areas may occur inwater systems in <BR> <BR> <BR> <BR> parts ofthe distribution deck, coolingtower sump, andinsystemdeadlegs. These studies further indicate that higher temperatures and increased flow rates can increase the susceptibility ofbiofilms <BR> <BR> <BR> towards biocides. The former effectmaybe dueto anincrease inmicrobialmetabolic activity atthe higher temperature; the latter due to increased biocide penetration into the biofilm <BR> <BR> <BR> [0021] Among disclosedresearch efforts directedto controlofbiofilms withbiocides are the following : [0022] Hypochlorous acid, hypobromous acid, and the halogen donor BrMEH (bromo-chloro-methylethylhydantoin) were tested againstbiofilms ofSplaaerotilus yzatans (M. L.

LudenskyandF. J. Himpler,"The Bffect ofHalogenatedHydantoins onBiofilms,"paperno. 405, Corrosion/97, NACE International, Houston, TX, 1997). Note that S. Natans forms robust, filamentaceous biofilms that are very resistant to biocidal treatment. Dynamic tests using non-destructive bio 61m monitoring techniques (heat transfer resistance and dissolved oxygen concentration) indicatedbiofilm control (but not eradication) at the following treatment levels : 10 ppmBrMEH, 15ppmHOBr, and>20ppmHOCl (i. e., chlorinedidnotcontrolthebiofilmatthe maximum applied dose of 20 ppm). Both bromine itself and the bromine donor BrMEH (bromochloromethylethylhydantoin) thus appeared more effective than chlorine in these tests.

[0023] Arecentstudycomparedtheefficacyofhydantoinproducts (BCDMH, BrMEH) towards both planktonic and biofilm bacteria (J. F. Kramer,"Biofilm Control with Bromo-Chloro-Dimethyl-Hydantoin,"paperno. 01277, NACElntelltational, Houston, TX, 2000).

Biofilmstudies were carried out on 5-to 7-daybiofilms generated onstainless steel cylinders grown in a laboratory flow-through system. Bothproducts dosed at 0.5 ppm (totalresidual as Cl2) gave > 4 log reductions in planktonic organisms after 1 hour. As expected, efficacy decreased against biofilm bacteria. At 1 ppmresiduals. BCDMH provided onlyal logkill ; BrMEH a 0. 7 log kill.

Efficacy of bothproducts towards biofilmbacteria improved slightly in the presence of ammonia.

CT (concentrationvs. time) studies suggest that it maybe better to dose alesser amount ofproduct for a longer period of time.

[0024] Chlorine dioxidehas beenshownto controlbiofilms. For example, 1. 5 mg/L C102 applied continuously for 18 hours in a flow-through systemreduced biofilm bacteria 99. 4%, (J. Walker and M. Morales,"EvaluationofChlorineDioxide (C102) forthe ControlofBiofilms,"WateScience and Technology, vol. 35, no. 11-12, pp. 319-323 (1997) ). Arecent field trial indicated effective biofouling control at an applied dose of 0. 1 mg/L, (G. D. Simpson and J. R. Miller, "Control of Biofilmwith Chlorine Dioxide,"paper presented at the AWT Annual Convention, Honolulu, HI, 2000).

[0025] Field studies were reported concerning anewly-registered combination ofperacetic acid (5. 1% w/w) and hydrogen peroxide (21.7% w/w) for cooling water treatment, (J. Kramer, "Peroxygen-Based Biocides for Cooling Water Applications,"presented at AWT Annual Meeting, Traverse City, MI, 1997). This biocide combination dosed every other dayto aresidual of about 10 ppm PAA and 40 ppm hydrogen peroxide (0.6 gallons/dose) provided effective control of sessile bacteria. Biofilm counts were about 1.5 to 2.5 logs vs. 2.5 to 4 logs for isothiazolone (5 gals, <BR> <BR> <BR> once/wk.,-20ppm a. i.). Recommended application rates ranged from 5-9 ppmPAA 2 to 3 times per week (fouled system) to 3-5ppmPAA2to 3 times perweek (clean system). It was suggested to alternate application of PAA with halogen-based biocides.

[0026] The performance of hydrogen peroxide and other biocides were investigated in a pilot cooling system at pH 9, (M. F. Coughlin and L. Steimel,"Performance of HydtogenPeroxide as a Cooling Water Biocide and its Compatibilitywith Other Cooling Water Inhibitors,"paperno. 397, ColTosion/97, NACE International, Houston, TX, 1997. Hydrogen peroxide at 2-3 ppm continuous as well as glutaraldehyde or THPS dosed to 50 ppmyielded 2-log reductions in sessile bacteria counts. A continuous chlorine residual of 0. 4 ppmprovided a 5-logreductioninbiofilm counts (to about 102 bacteria/in2).

[0027] Abiofouling studywas reportedwithhydrogenperoxide inaonce-throughcooling system.

(J. F. Kramer,"PeraceticAcid : ANew Biocide for IndustrialWaterApplications,"paperno. 404, Con osion/97, NACE International, Houston, TX. ) Levels of 5 ppmhydrogenperoxide provided better control than 0.1 ppm chlorine. The biocides were dosed for 2 hours/day.

[0028] Legionella pneumophila often thrives in sessile microbial communities. A review of control strategies forthis problemmicroorganismwas presentedin 1999. (G. D. SimpsonandJ. R.

Miller, "Chemical Control of Legionella,"paperpresentedattheAWTAnnual Convention, Palm Springs, CA, 1999.) A study ofthe effect ofbiocides onbiofilms containingPseudomonas species, Legionella py2eumophila, and amoebae in pilot cooling towers was also described in 1999. (W.

M. Thomas, J. Eccles, and C. Fricker,"Laboratory Observations of Biocide Efficiency against LegionellainModel Cooling Tower Systems, "paper SE-99-3-4, ASHRAE Transactions (1999.) This workindicatedthat chlorine (0-5 ppmresidual) andbromine (0-2 ppmresidual) effectively controlledbiofilmbacteria over a4-dayperiod (the duration ofthe experiment) with about 4 and 3 log reductions, respectively. Halogen residuals varied widely but never exceeded 5 ppm for chlorine and 2 ppm for bromine. Non-oxidizing biocides were not as effective in thes e tests with polyquat having essentially no effect on biofilm bacteria. Some of the biocides proved more effective at controllingbiofilin-associatedLegionella. For example, in addition to chlorine and bromine, both dibromonitrilopropionamide (DBNPA) and glutaraldehyde reduced biofilm-associatedLegionella to non detectable levels. Bothpolyquat and ozone treatments did not appear to significantly affect levels of biofilm-associated Legionella.

[0029] Results of an investigation of the efficacy of five different biocides on two-week old biofilms consisting of a consortium ofLegionella, heterotrophic bacteria and amoebae have been reported. (E. McCall, J. E. Stout, V. L. Yu, and R. Vidic,"Efficacy of Biocides against Biofilm-AssociatedLegionellainaModel System,"paperno. IWC 99-70, International Water Conference, Engineers Society ofW. Pennsylvania, Pittsburgh, PA, 1999.) The biocide contact time was 48 hours. Chlorine levels of 2 to 4 ppm provided rapid reductions in both <BR> <BR> <BR> biofilm-associatedheterotophic bacteria andbiofilm-associatedLegionella. BCDMHat lOppm was also effective but was slower acting. Glutaraldehyde was effective when dosed at 100 ppm active. Carbamate and polyquat were least effective.

[0030] Another study has demonstrated that certain biocides offer enhancedlong-term control <BR> <BR> <BR> ofbiofilmorganisms. AstabilizedbromineproductprovidedlongertermcontrolofMICthan either sodiumhypochlorite or sodiumhypobromite. (M. Ensignand B. Yang,"Effectiveuse of Biocide for MIC Control in Cooling Water Systems, "paper no. 00384, Corrosion/2001, NACE International, Houston, TX, 2000. ) Apatentedlocalizedcorrosiontechniquewasusedto measure effects of different biocide treatment regimens in both laboratory and pilot plant cooling tower systems.

[0031] In general, most ofthe biofilmwork to date indicates oxidizing biocides such as chlorine and bromine are more effective against biofilm bacteria and biofilm-associated Legionella than other biocides. Biofilm-associatedLegioyaella exhibits enhanced susceptibilityto biocide treatment and some non-oxidizing biocides, glutaraldehyde and DBNPA, appear effective in this case. Certain non-oxidizing biocides such as polyquat have not been shown to control biofilm bacteria or <BR> <BR> <BR> biofilm-associatedLegionella. Use ofsuchbiocides should onlybeusedincombinationwith other more effective biocides for control of bioHlm-relatedproblems. Recent studies indicate that biocides exhibit differences not only interns ofioitial emcacy but in terms ofthe length ofrecovei y ofbiofilms after biocide application.

[0032] Papers suggesting improved control ofbiofdm organisms by using combinations of biocides have also appeared. In one study, biofilms of Sphaerotilus natans in a laboratory flow through systemweretreatedwithcombinations ofisothiazolone andbrominatedhydantoin (BrMEI). (M. L.

Ludensky, F. J. Himpler, and P. G. Weeny,"Control of Biofilms with Cooling Water Biocides," paper no. 522, Corrosion/98, NACE International, Houston, TX, 1998. ) The combination ofinitial application ofisothiazolone isothiazolone (4 ppmai) followedwithin onehourbyBrMEH (10 ppm, <BR> <BR> <BR> as total C12) providedthebestlong-termandcosteffectivecontrolofbiofilmbact eriabased onDO (dissolved oxygen) and HTR (heat transfer resistance measurements). In another study, a combination of BNPD/ISO, a synergistic blend of 5. 3% 2-bromo-2-nitro-1, 3-propanediol and 2.6% isothiazolones, was studied as a replacement for gaseous chlorine. (L. G. Kleina, et. al., "PerfoimanceandMonitoringofaNewNonoxidizingBiocide : The Study of BNPD/ISO and ATP," paperno. 403, Corrosion/97, NACE International, Houston, TX, 1997.) Afieldtrialinarefineiy cooling tower (140,000 gallon capacity) indicated that 65 mg/L applied twice per week provided bettercontrol of biofilmbacteriathan 0.2 to 0.6 mg/L free continuous chlorine. Biofilm counts were determined by ATP measurements. About 50 mg/L product provided equivalent performance to the chlorine system (-1. 0 x 104 RLU/cm2). <BR> <BR> <BR> <P>[0033] Certain surfactants orbiodispersants have been applied to cooling water systems to help loosenup deposits arising fi ombuildup ofscales, microorgaziisms, and foulingmaterials (clay, iron, <BR> <BR> <BR> etc. ). Such surfactants typicallyhavebeenusedin combinationwith celtainbiocides. Surfactants have been considered for both biofilm prevention and removal.

[0034] Certain nonionic surfactants, for example, were shown to reduce bacterial colonization of 316 SS coupons. (W. K. Whitekettle, "Effects of Surface-Active Chemicals on Microbial Adhesion," Journal of Industrial Microbiology, vol. 7, pp. 105-166 (1991)). Tests indicated 2-3 log reductions in bacterial populations over a 4-day period at continuous surfactant dosages of 10 ppm. The best surfactants provided a high reduction in surface tension (>20mN/m). l0035] Studies ofthe effect ofEO/PO block copolymer on flhn fill fouling indicate the surfactant alonewasnotabletoprovidelongtermcontrol. (R. M. Donlan, D. L. Elliott, andD. L. Gibbon,"Use of Surfactants to Control Silt and Biofilm Deposition onto PVC Fill in Cooling Water Systems," IWC-97-73, Engineers'Society of Western Pennsylvania, Pittsburgh, PA, 1997. ) Continuous addition of 250 ppm block copolymer in a model recirculating water system reduced bacterial colonization for 14 days but little effectiveness was observed after 35 days. A combination of EO/PO (50 mg/L) togetherwithslug doses of glutaraldehyde (60 mg/L, 3x/week) reduced solids accumulation significantly relative to controls with no biocide or surfactant treatment.

[0036] Use of aproprietaryaniorlicbiodetergent (linear alkylbenzenesulfonate, applied at 5 ppm) together with normal activated sodium bromide treatment removed resulted in a gradual removal of deposits onfilmfillsurfaces. (F. P. Yu, et al.,"Cooling TowerFill Fouling Controlin a Geothermal Power Plant, "paper no. 529, Corrosion/98, NACE International, Houston, TX, 1998. ) This treatment also restored cooling tower operating efficiencywhichwas gradually eroded under the previous biodispersant program.

[0037] An improved biodetergent has been developed which consists of an alkylpolyglycoside (APG) containing C8 to C16 alkyl groups. (F. P. Yu, et al.,"Innovations inFillFouling Control, " IWC-00-03, Engineers' Society of Western Pennsylvania, Pittsburgh, PA, 2000. ) Theproductis reported possess"... both dispersancy (dispersing aggregates) inthebulkwater and detergency (removing biofilmmatrix) inthe solid/liquidinteiphase."One case study in a coal-firedpowerplant indicated that daily slug doses of 20 ppmAPGwith activated sodium bromide (0.5 ppmfiee) provided immediate increases in levels of protein and ATP in the bulk water and dramatic improvements in cooling tower thermal efficiency relative to the activated bromide-only treatment.

A second study in a different coal-fired plant indicates that continuous dosages of 20 ppmAPG together with BCDMH (0. 1-0. 2 ppm) gradually led to reduced biomass accumulations on test coupons.

[0038] 2- (Decylthio) ethanamine (DTEA) is a product that is offered as both a biocide and biodispersant. Several case studies of DTEA which indicated removal of slimes and biofouling deposits have been described. (A. G. Relenyi, "DTEA : A New Biocide and Biofilin Agent, " presentedatAWTAnnualMeeting, Colorado Springs, CO, 1996.) For example, biofilmthatwas plugging nozzles on a distribution deck was removed following three doses of DTEA (15 ppm active) on alternate days together with low chlorine residuals. Additional studies indicate control of biofilmwithtwice weekly slug dosages ofDTEA (20 ppm active) as indicatedbyATP andbiofilm thickness measurements. The product also controls biofouling of film-fillwhereits perfomzancewas <BR> <BR> attributedto disruption ofbioflmviachelation ofCa scale. The generalrecommendationfor open loop systems is to apply 1 to 25 ppmDTEA as active 2 to 3 xperweek. The product is also said to be a good algaecide.

[0039] A formulation that ibrms a film on surfaces to inhibit corrosion, disperse slimes, scales, and algae, and controlmacrofouling has been discussed. (R. T Kreuser, et al.,"ANovelMolluscide, ColTosionlihibitor, andDispersant,"paperno. 409, ColTosion/97, NACE International, Houston, TX, 1997.) One fieldstudyinvolvedahotelcomplexwhichusedharborwaterfor cooling. The systemhad severe foulingproblems, reducedheattransfer andpluggedtubes. Treatmentwithfilin forming formulation (6 mg/L) for one hour daily resulted in a reduction of black, slimy deposits in the tubular heat exchangers after one week and complete removal of the deposits after one month of application.

[0040] Use of enzymes canbe considered an emerging technology. Enzymes are proteins isolated fiomliving organisms--plants, animals, microorganisms--that speedup certain chemicalreactions. Certain enzymes such as acidic and alkaline proteases, carbohydrases (e. g. , amylases), and esterases (e. g., lipases) accelerate the hydrolysis of organic compounds. These enzymes have been used to help prevent or remove the outer slime layer (EPS) of biofilm deposits.

[0041] Areview ofthe use of enzymes to control slimes, biofouling and MIC appeared several years ago. (R. W. Lutey,"Enzyme Technology: A Tool for the Prevention and Mitigation of MicrobiologicallyInfluenced Corrosion,"IWC-97-71, Engineers'Society of WesternPennsylvania, Pittsburgh, PA, 1997.) One suggestedmethodforremoving accumulatedlayers of sessilebiomass involves amulti-step process involving addition of one amylase, one acidic/alkaline protease, and an anionic surfactant. Tests on slime forming organisms isolated frompaper machine deposits indicate that the use ofthis enzyme formulation (each component added at 20 ppm) significantly reduced pressure drop in a fouled stainless steel tube. The enzyme combination apparently hydrolyzes the EPS associated with the biomass and detergent helps flush the deposit off the substrate. The appeal of this technology is that enzymes are relatively non-toxic and are of natural origin. However, this approach still remains to be proven as general and cost effective method for biofouling control.

[0042] Despite intensive research studies such as those referred to above, it would be of considerable advantage if away could be found of achieving stillmore effective and/or longer lasting eradication or control of biofilminwater systems, such as industrial andwastewater systems, and especially biofilms harboring pathogenic species.

THE PRESENT INVENTION [0043] Pursuant to this inventionthe effectiveness of effective biocides is potentiated byuse of abiodispersanttherewith. Itis believedthatthe biodispersants used facilitate penetration of the defensive polysaccharide shields or layers ofthe biofilmbythe biocidal species released in the water by the highly effective biocides used in the practice of this invention. In this way the biocidal species can exert their devastating effects upon the active biofilm andpathogen species within the heart of the normally penetration-resistant biomass. And since in many cases the rate of penetrationbythe biocidalspecies is relativelyrapid, theirbiocidal activities withinthe biomass tend to be longer lasting.

[0044] Thebiocides usedinthepractice ofthis inventionare one ormorebrominebased-biocides comprising (i) asulfamate-stabilized, bromine-basedbiocide or (ii) at least one 1, 3-dibromo-5,5- diallcylhydantoininwhich each ofthe alkylgroups, independently, contains intherange of 1 to about 4 carbon atoms, the total number of carbon atoms in these two alkyl groups not exceeding 6, or both of (i) and (ii). Ofthese biocides, sulfamate-stabilized, bromine-basedbiocides, especially a sulfamate-stabilized bromine chloride solution are preferred. Aqueous solutions comprised of one or more active bromine species, said species resulting from a reaction in water between bromine, chlorine, or bromine chloride, or anytwo or allthreethereof areparticularlyprefemedwhenused in combinationwith abiodispersant pursuant to this invention. Such aqueous solutions of bromine species andbiodispersantpossess the advantageous property of effectively coordinating rate of penetration andrate of kill of biofilmsuchthatthebiocidalactivityofthe solutionis notprematurely lost or severely depleted during the penetration of the protective polysaccharide films generatedby the biofilm pathogens.

[0045] Thus, in the practice ofthis invention highly effective results can be achieved by use of a bromine-based microbiocide comprising an aqueous microbiocidal solution comprised of one or more active bromine species, said species resulting from a reaction in water between bromine, chlorine, or bromine chloride, or any two or all three thereof, and a water-soluble source of <BR> <BR> sulfamateanion, especiallywherethemolarratio of bromineto chlorineis equalto orgreaterthan 1. Suchwater solutions are usually provided as a concentrated solution which may contain at least 50,000 ppm (w/w), preferably at least 100,000 ppm (w/w) of active bromine, and still more preferably at least 160,000 ppm (w/w) of active bromine. When used by addition to a body of water in contact withbiofilm, orthat comes into contactwithbiofìlm, such concentrated solutions orpartially dilutedsolutions formedtherefiomare addedto orotherwiseintroducedinto the body <BR> <BR> ofwaterto provide amicrobiocidally effective amount of active brominetherein. When used by application to a surface such by use of an applicator (mop, cloth, etc. ) the concentrate can if necessary be used as received. However usually the concentrate will be diluted before such application.

[0046] Anaqueousmicrobiocidalsolutionofatleastonel, 3-dibromo-5, 5-dialkylhydantoinin which each ofthe alkyl groups, independently, contains intherange of 1 to about4 carbonatoms, the total-number of carbon atoms in these two alkyl groups not exceeding 6 can also be effectively used in the practice ofthis invention. Such aqueous solutions are typically formed by dissolving a suitable quantity ofthe 1, 3-dibromo-5, 5-dialkylhydantoininwaterto formasolution containing a microbiocidally effective amount of active bromine therein.

[0047] Water-soluble 1,3-dibromo-5, 5-dialkylhydantoinsutilizedinthepracticeofthisinvention comprise 1, 3-dibromo-5, 5-dimethylhydantoin, 1, 3-dibromo-5-ethyl-5-methylhydantoin, 1,3- dibromo-5-n-propyl-5-methylhydantoin, 1, 3-dibromo-5-isopropyl-5-methylhydantoin, 1,3- <BR> <BR> dibromo-5-n-butyl-5-methylhydantoin, 1, 3-dibromo-5-isobutyl-5-methylhydantoin, 1, 3-dibromo-5- sec-butyl-5-methylhydantoin, 1, 3-dibromo-. 5-tert-butyl-5-methylhydantoin, l, 3-dibromo-5, 5- diethylhydantoin, andthelike. Mixtures of anytwo ormore ofthese can be used. Ofthesebiocidal agents, 1, 3-dibromo-5-isobutyl-5-methylhydantoin, 1, 3-dibromo-5-n-propyl-5-methylhydantoin, and 1, 3-dibromo-5-ethyl-5-methylhydantoin are, respectively, preferred, more preferred, and even more preferredmembers ofthis group fromthe cost effectiveness standpoint. Ofthemixtures of these biocides that can be used pursuant to this invention, it is preferred to use 1, 3-dibromo-5,5- dimethylhydantoin as one ofthe components, with amixture of l, 3-dibromo-5, 5-dimethylhydantoin and 1, 3-dibromo-5-ethyl-5-methylhydantoin being particularly preferred. The most preferred biocide employed in the practice of this invention is 1, 3-dibromo-5,5-dimethylhydantoin.

[0048] Amethodforpreparingbromine-basedbiocides oftype (i) is describedinU. S. Pat. No.

6, 068, 861. Apreferred bromine-based biocide oftype (i) inthe formofa concentrated aqueous solution with an alkaline pH is available in the marketplace under the trade designation STABROM 909 biocide (Albemarle Corporation). Thus by"sulfamate-stabilized bromine chloride"is meant aproduct such as STABROM 909 biocide or that canbe formed for example by the inventive processes describedinU. S. Pat. No. 6, 068, 861. Bromine-basedbiocides oftype (ii) typically exist as particulate solids, and methods for preparing them are described in the literature. The most preferred bromine-based biocide of type (ii), namely 1, 3-dibromo-5,5- dimethylhydantoin, in the form of easy-to-use granules is available in the marketplace from Albemarle Corporation under the trade designation XtraBromTM 111 biocide.

[0049] Thepowerful activity ofthesepreferredbiocides inchallenging or eradicatingbiofilmwas demonstrated in a group of comparative tests. In these tests, awide range ofbiocides used inboth industrial and recreational water treatment towards biofilms comprised of Pseudomonas aeruginosa.

[0050] ThetestswereperformedatMBECBiofilmTechnologies, Inc. , Calgary, Canada. The test procedure, developed at the University of Calgary, utilizes a device which allows the growth of <BR> <BR> <BR> 96 identicalbiofilms under carefully controlled conditions. The device consists of atwo-palt vessel comprised of an upper plate containing 96 pegs that seals against abottomplate. The bottomplate can consist of either atrough (forbiofilmgrowth) orastandard96-wellplate (forbiocide challenge). <BR> <BR> <BR> <P>Thebiofilmn develop onthe 96 pegs. Thedevicehas beenusedasageneralmethodfor evaluating the efficacy of antibiotics andbiocides towards biofilms. See intlis connectionH. Ceri, et al.,"The MBEC Test: ANewIn VitroAssayAllowingRapidScreeningforAntibiotic SensitivityofBiofilm", Proceedings oftheASM, 1998, 89, 525; Ceri, et al., "Antifungal and Biocide Susceptibility testing of Candida Biofilms using the MBEC Device", Proceedings of the Interscience Conference on Antimicrobial Agents and Chemotherapy, 1998, 38, 495; and H. Ceri, et al.,"The CalgalyBiofilmDevice : ANew Technology for the Rapid Determination of Antibiotic Susceptibility of Bacterial Biofilms", Jounal of Clinical Microbiology, 1999, 37, 1771-1776.

[0051] Thirteen biocide systems were evaluated using the above test procedure and test equipment. Six ofthese systems were oxidizing biocides, viz., chlorine (fromNaOCI), halogen (fi omNaOCl + NaBr), bromine (fi om sulfamate-stabilized bromine chloride), bromine (from DBDMH), halogen (fromBCDMH), and chlorine (fromtrichloroisocyanuric acid) (Trichlor), all expressed as Cl2inmg/L, so that all test results were placed on the same basis. The other biocides tested were glutaraldehyde, isothiazolone, (2-decylthio) ethanamine (DTEA), peracetic acid, hydrogenperoxide, poly (oxyethylene (dimethyliminio) ethylene-(dimethylimino)ethylenedichloride) (Polyquat), anddibromonitrilopropionamide (DBPNA). These other biocides are all expressed as mg/L of active ingredient.

[0052] These biocide systems were used to challenge biofilms of Pseudomonas aeruginosa (ATCC 15442). This is aGram (-) bacteriumwhichis ubiquitous inmicrobiologicalslimes found in industrial and recreationalwater systems. See inthis connection J. W. Costerton and H. Anwaqr, "Pseudomonas aeruginosa : The Microbe and Pathogen", in Pseudomonas aerugionosa Infections and Treatment, A. L. BaltchandR. P. Smith editors, Marcel Dekker publishers, New York, 1994.

Tests were performed using 1-day old biofilm and 7-day old biofilm.

[0053] In Table 1 theMBEC (rninimumbiofilmeradicationconcentration) resultspresentedare for the one-hour biocide contact time used in the tests (except as otherwise noted). The values given for the halogen containing biocides are expressed in terms of chlorine as Cl2mg/L as active ingredient. The ta indicate that the DBDMH used pursuant to this invention was more effective than any of the other biocides tested under these conditions with an MBEC of 1. 4 mg/: L of chlorine, as Ck. In fact, onlyslightlymore than one-halfas muchtotalhalogenresidualfiomDBDMHwas requiredtoremovethebiofilmas comparedto thetotalresidualhalogen, expressedas Ck, thatwas required from BCDMH [0054] Table 1 summarizesthesetestresults. The abbreviations or designationsusedintheTable are as follows: SSBC-stabilized bromine chloride; DBDMH-1-3-dibromo-5, 5-dimethylhydantoin ; BCDMH-l-bromo-3-chloro-5, 5-dimethylhydantoin; Trichlor-1,3, 5-trichloroisocyanuric acid; Isothiazolone-5-chloro-2-methyl-4-isothiazolin-3-one/2-methy l-4-isothiazolin-3-one mixture ; DTEA-decylthioethaneamine hydrochloride; Polyquat-poly (oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylenedichloride); DBNPA-Dibromonitrilopropionamide.

TABLE 1 Minimum Biofilm Eradication Concentration (MBEC) for Selected Biocide Systems (One Hour Contact Time) Biocide System 1-Day Biofilm 7-Day Biofilm MBEC, ppm MBEC, avg. MBEC, ppm MBEC, avg. Bleach (NaOCl) 5.0, 2.5 3.8 20,20 20 Activated NaBr 2.5, 2.5 2.5 5,10 7.5 (NaOCI + NaBr) SSBC 2.5, 5 3.8 5, 5 5 DBDMH 1, 2 1.2 5,5 5 BCDMH 2.5, 2.5 2.5 5,10 7.5 Trichlor 2. 5,1. 2 1.9 20,20 20 Glutaraldehyde 50,50 50 100, >200 200 (est.) Isothiazolone 50,100 75 ---- ---- DTEA 100,100 100 Peracetic Acid (1) 100, >100 150 (est.) H2O2 (1) >100, >100 >200 (est) Polyquat >400, >400 >400 ---- ---- DBNPA 2.0, 4.1 3. 1 ---- ---- (1) Four-hour contact time.

[0055] ItwillbeseenfiomTable 1 thatespeciallyinthetests againstolder, morematurebiofilms the bromine-based biocides of this invention were very effective. It is known that as biofilms age theycanbecomemoreresistanttobiocidetreatment. Seeintliis connectionP. S. Stewart,"Biofilm Accumulation Model that Predicts Antibiotic Resistance ofpseudomoizas aeruginosa Biofihus, Antimicrobial Agents and Chemotherapy, p. 1052, May, 1994.

[0056] Additional tests were conducted on SSBC and DBDMH, as well as bromine from activated sodium bromide (aproduct formed fiomNaOCI andNaBr) using a laboratory model water system described by E. McCall, J. E. Stout, V. L. Yu,. and R. Vidic, "Efficacy of Biofilms AgainstBiofilm-AssociatedLegionella inaModelSystem,"InternationalWater Conference, paper no. IWC-99-70, Engineers' Society of Western Pennsylvania, Pittsburgh, PA. In these short-term tests allthree biocides provedeffective againstbiofilm-associatedLegionella withinitial 3 to 3. 8 <BR> <BR> <BR> logreductions inbacteria counts. The biocides also controlledPlanktonicLegioyiella withinitial reductions of 3.6 to 4 log units. The results of these tests are summarized in Table 2.

TABLE 2 Biocide Residual, Log Reduction, Legionella2 Log Reduction, HPC Bacteria2 Max. as C12 Planktonic Biofilm Planktonic Biofilm SBC 4.1 3.9 3 2.2 2.2 DBDMH 1.9 3.6 3.6 3.6 2.7 Act. 1.7 3.8 3.8 3.4 3.7 NaBrl 1SBC = stabilized bromine chloride; DBDMH = dibromodimethylhydantoin; Activated NaBr = NaOCl + NaBr.

2 Maximum log reductions were typically obtained at 2-12 hours after biocide application.

[0057] As is well known, bacteria can repopulate to pre-biocide levels after removal of the biocide or"stress". The above tests not only monitored the activity of the biocides to control bacteria initially but over the long-term as well. Long-term controlwas simulated by flushing the remaining biocide out ofthe system after the 48-hour biocide challenge period and then refilling the system with sterile chlorine-free water. Microbial populations were then monitored over a <BR> <BR> <BR> two-weekrecoveryperiod. This workuncoveredsignificant differences betweenthebiocides of this invention and the comparative biocide towards long-termcontrol of bacteria. These test results are summarized in Table 3.

TABLE 3 Biocide Log Reduction, Legionella1 | Log Reduction, HPC Bacteria Planktonic Biofilm Planktonic Biofilm SBC 3.7 1.8 1.4 0. 8 DBDMH 1.7 1.5 0.2 0.4 Act. NaBr-0. 1 0. 1 0. 2 0.3 Log reductions relative to control after the 14-day recovery period.

[0058] BothSBC andDBDMHmaintainedlong-lasting controlofbacteriainboththebiofilmand planktonic phases. At the conclusion of the 14-day recovery period, for example, biofilm- associatedLegionella counts remained 1. 5 to 1. 8 log units lower thanthe untreatedvalues. Good control of planktonic Legionella was also observed with these biocides. <BR> <BR> <BR> <P>[0059] In addition to improvedbiocidal effectiveness, this invention provides a combination of additional advantages. For example, 1, 3-dibromo-5, 5-dimethylhydantoin (DBDMH) in combination with a conventional biodispersant package, has been found to provide superior performance at a lower rate of consumption than N, N'-bromochloro-5, 5-dimethylhydantoin (BCDMH) when used with the same conventional biodispersant package. In addition, the DBDMH/biodispersant package exhibited amuch faster development of target halogenresiduals which couldnotbe achievedwiththe BCDMHlbiodispersantpackage. Further, it was observed that the visual water depth in the basin ofthe cooling tower was increased from 10-12 inches to more than 23 inches by use ofthe DBDMH/biodispersant package. These tests were performed in atwin cell, counterflow cooling tower having a 200, 000 gallon capacity and itwas foundthat the rate of consumption was reduced by about 1/3 by use of DBDMH/biodispersant package as compared to BCDMH/biodispersant package. The biodispersant package used contained a proprietarybiodispersant, andinaddition l-hydroxyethane-l, l-diphosphonic acid (HEDP), 2- phosphonobutane-1, 2, 4-tricarboxylic acid (PBTC), tolyltriazole (TT), andsodiummolybdate. The materials of construction of the cooling tower system consisted ofawood tower, concrete basin, copper heat exchangers and mild steel piping. It was found that the corrosion rates of both mild steel and of copper were significantly reduced by use ofthe DBDMH/biodispersant package as comparedto the BCDMH/biodispersantpackage. Inparticular, onmildsteeltherate of corrosion after a five week exposure using the BCDMHJbiodispersantpackagewas 3.6 mils per year whereas after a sixweek exposure using the DBDMHibiodispersantpackage, this rate of corrosion was a mere 1. 2 mils per year. In the case of copper corrosion, the rates of corrosion were 0. 06 mils per year with the BCDMH/biodispersant package in a five week exposure period, and 0. 05 mils per year with the DBDMH/biodispersant package in a six week exposure period. <BR> <BR> <BR> <P>[0060] Effective biodispersants usedinthe practice ofthis invention canbe selectedfiomvarious types of surfactants, including anionic, nonionic, cationic, and amphoteric surfactants. Anumber of suitably effective surfactants for this use are available in the marketplace. A few non-limiting examples of anionic surfactants deemed suitable for the practice of this invention include such surfactants as (a) one or more linear alkyl benzene sulfonates in which the alkyl group has in the range of about 8 to about 16 carbon atoms, (b) one or more alkane sulfonates having in the range of about 8 to about 16 carbon atoms in the molecule, (c) one or more alpha-olefin sulfonates having in the range of about 8 to about 16 carbon atoms in the molecule, and one or more diallyl disulfonates in which the aryl groups each contain in the range of 6 to about 10 carbon atoms.

Mixtures of any two or three or all four of (a), (b), (c), and (d) can be used. The cation of such sulfonates is typically sodium, but sulfonates with other suitable cations such as the ammonium or <BR> <BR> <BR> potassium cations are suitable. Surfactants of the above types are available commercially from a number of sources, and methods for their preparation are described in the literature.

[0061] Non-limiting examples of nonionic surfactants deemed suitable for the practice of this invention include such surfactants as (a) one ormore alkylpolyglycosides inwhichthe alkylgroup contains in the range of about 8 to about 16 carbon atoms and the molecule contains in the range of 2 to about 5 glycoside rings in the molecule and (b) one or more block copolymers having repeating ethyleneoxideandrepeatingpropylene oxidegroups inthemolecule. Mixtures of (a) and (b) canbe used. Various alkylpolyglycosides of (a) are available commercially and are described for example in U. S. Pat. No. 6, 080, 323. Similarly, block copolymers of (b) are available commercially, and are described andidentifiedfor example in U. S. Pat. No. 6,039, 965. The block copolymers of (b) are expected to function in this invention at least primarily by weakening the bondingbetweenthe biofilminfestation andthe substrate surface to which the biofilm is attached, although they may assist somewhat in improving penetration of the active bromine through the protective polysaccharides and into the biofilm infestation.

[0062] Another group of biodisperant (s) for use in the practice ofthis invention are nitrogen- containing surfactants some of which are amphoteric or cationic surfactants, especially amines and amine derivatives having surfactant properties. One group of preferred compounds are aklthioethanamine carbamic acid derivatives such as are described inU. S. Pat. Nos. 4,816, 061, 5,118, 534, and 5, 155, 131. Ofthese carbamic acid derivatives those in which teh alkylthio group has about 7 to about 11 carbon atoms are preferred, those in which the alkylthio group has 8 to 11 carbon atoms are more preferred, with 2- (decylthio) ethanamine being particularly preferred.

Another group of suitable amine-based surfactants are alkyldimethylamines, alkyldiethylamines, alkyldi (hydroxyethyl) amines, alkyldimethylamine oxides, alkyldiethylamine oxides, and alkyldi (hydroxyethyl) amine oxides inwhichthe alkylgroup contains intherange of about 8 to about 16 carbon atoms. Still other suitable nitrogen-containing compounds for this use include alkylguanidine salts such as dodecylguanidine hydrochloride or tetradecylguanidine hydrochloride, and tallow hydroxyethyl imidazoline. Mixtures of the same and/or of different types of these nitrogen-containing surfactants can be used.

[0063] Among preferred surfactants for use in the practice of this invention are alpha-olefin sulfonates, internal olefin sulfonates, paraffin sulfonates, aliphatic carboxylates, aliphatic phosphonates, aliphaticnitrates, andalkylsulfates, whichhave anHLB of 14or above. Examples of such surfactant types can be found in McCutcheon's Emulsifiers and Detergents, North <BR> <BR> AmericanEdition, andInternationalEdition, 1998Annuals. InsituationswheretheHLB of agiven candidate for use as component (ii) is not already specified, the HLB canbe calculatedusing the method described by J. T. Davies, Proc. 2nd Int. Congr. Surf Act., London, Volume 1, page 426. Also see P. Becher, Surfactants in Solution, Volume 3, K. L. Mittal, Ed. , Plenum, New York, 1984; J. Disp. Sci. & Tech., 1984, 5, 81. Itwillbenotedthat surfactants meetingthe HLB requirement of 14 or above have relatively small molecular structures as comparedto surfactants <BR> <BR> widely-used for laundry applications. Afew additionalnon-limiting examples oftheseprefemed surfactants are 1-hexene sulfonate, 1-octene sulfonate, and Cs paraffin sulfonate. The first two of these can be prepared by direct sulfonation of 1-hexene and 1-octene, respectively, followed by deoiling. Theparaffinsulfonate (e. g., am1xture of 52% mono-sulfonate and48% of disulfonate) can be prepared using bisulfite addition of 1-octene, followed by oxidation and deoiling.

[0064] Othertypes ofbiodispersants canbe used, especiallybiodispersants which are inthe liquid<BR> <BR> <BR> stateorformulatedtobeintheliquidstate. Suchliquidsarereadilyblendedwithbiocidalsolutions of sulfamate-stabilized, bromine-basedbiocideand/orbiocidalsolutions formedfiom 1, 3-dibromo- 5, 5-diaklhydantoin which each of the alkylgroups, independently, contains intherange of 1 to about 4 carbon atoms, the total number of carbon atoms in these two alkyl groups not exceeding 6.

[0065] The concentations ofthe bromine-basedbiocide andthe biodispersant (s) inthe aqueous mediumin contanct with, or that comes into contactwith, the biofilmcanbe variedwithinwide limits.

Such concentrations andrelative proportions can depend on such various factors as the identity of the biodispersant or biodispersants being used, the type and severity ofthe biofdminfestation, the nature of any pathogens contained within the biofilm infestation, and the like. As a general proposition, the amount ofthebromine-basedbiocide used shouldbe an effective microbiocidal <BR> <BR> amount, i. e. , an amount thatwhen acting in combinationwiththebiodispersant (s) used is effective to eradicate or at least substantially eradicate the biofilmand the pathogens, if any, present therein, and the amount ofthe biodispersant (s) usedwith the biocide shouldbe an effective potentiating amount, i. e. , an amount that is effective to improve the microbiocidal effectiveness ofthe biocide.

Typically, the concentrations of active bromine and ofthebiodispersant inthe aqueous mediumin contact with or that comes into contact with the bionim are, respectively, amicrobiocidally-effective amount of active bromine that is at least 0.1 ppm (w/w), and an effective potentiating amount of at least 1 ppm (w/w) ofthe biodispersant (s). Prefemed concentrations are intherange ofabout 0. 2 to about 10 ppm (w/w) of active bromine and in the range of about 2 to about 50 ppm (w/w) ofthe biodispersant (s). More preferred concentrations are in the range of about 0.4 to about 4 ppm (w/w) of active bromine and in the range of about 5 to about 25 ppm (w/w) of the biodispersant.

Departures fi these concentrations canbe usedwheneverdeemednecessary or desirable without departing from the scope of this invention. As noted above, the mechanism by which the potentiation of this invention occurs is believed to involve, in part if not inwhole, the biodispersant (s) facilitating penetration ofthe aqueous active bromine into the active center (s) or core ofthe biofilm colony. It is also possiblethatthebiodispersantweakens thebonding betweenthebiofiltninfestation and the substrate surface to which the biofUm is attached.

[0066] To determine the amount of active bromine in me water in the low ranges of concentrations describedintheirimzediatelyprecedingparagraph, thewell-knownDPD"totalchlorine"test, should be used. While originally designed for analyzing relatively dilute chlorine-containing solutions, the procedure is readily adapted for use in determining active bromine contents of relatively dilute solutions as well. In conducting the test the following equipment and procedure are recommended : 1. The water sample should be analyzedwithin a few minutes of being taken, and preferably immediately upon being taken.

2. Hach Method 8167 for testing the amount of species present in the water sample which respondto the"totalchlorine"test involves use oftheHachModelDR2010 colorimeter.

The storedprogramnumber for chlorine determinations is recalledbykeying in"80"onthe keyboard, followedby setting the absorbancewavelengthto 530 nmbyrotatingthe dialon the side oftheinstrument. Two identicalsample cells are fìlledto the 10 mLmarkwiththe water under investigation. One of the cells is arbitrarily chosen to be the blank. To the second cell, the contents of a DPD Total Chlorine Powder Pillow are added. This is shaken for 10-20 seconds to mix, as the development of a pink-red color indicates the presence of species inthewaterwhichrespondpositivelyto theDPD"totalchlorine"testreagent.

On the keypad, the SHIFT TIMER keys are depressed to commence a three minute reaction time. After three minutes the instrument beeps to signalthe reaction is complete.

Using the 10 mL cell riser, the blank sample cell is admitted to the sample compartment of the Hach Model DR 2010, and the shield is closed to prevent stray light effects. Then the ZERO key is depressed. After a few seconds, the display registers 0.00 mg/L C12. Then, the blank sample cell used to zero the instrument is removed from the cell compartment of the Hach Model DR 2010 and replaced with the test sample to which the DPD"total chlorine"test reagent was added. The light shield is then closed as was done for the blank, and the READ key is depressed. The result, in mg/L C12 is shown on the display within a few seconds. This is the"total chlorine"level of the water sample under investigation.

3. To convert the result into mg/L active Br2, the result is multiplied by 2.25.

[0067] Frequency of dosage can also vary depending upon such factors as the type and severity ofthe biofilminfestation, the nature of any pathogens containedwithinthe biofilminfestation, the local climate conditions such as extent of direct exposure to sunlight, or the like. Generally speaking, one should dose the water systemwith sufficient frequency to ensure that effective substantially continuous control or eradication ofbiofilmis accomplished. For example, under typical conditions <BR> <BR> the water system should be dosed at intervals in the range of2 to 7 days andpreferably in the range of 1 to 3 days.

[0068] It is possible pursuantto this invention to form aqueous concentrates of the active bromine- containing biocides ofthis inventiontogether with an appropriate proportion ofthe biodispersant (s).

In such cases the weight ratios as between the active bromine and the biodispersant should correspond to those set forth above in connectionwiththe dilutedwater systems, except of course thatthe actualamounts ofthese components inthe aqueous concentrate willbe substantially higher.

For example, a concentrate containing, say, 50,000 to 120,000 ppm of active bromine (w/w) will typically contain in the range of 1, 000to 100, 000ppmofbiodispersant (s), and preferably in the range of 10,000 to 50,000 ppm of biodispersant (s).

[0069] Water systems that can be treated pursuant to this inventionto eliminate oratleast control biofilminfestations include commercialandindustlialrecirculating coolingwater systems, industrial once-through cooling water systems, pulp andpapermillsystems, airwasher systems, air and gas scrubber systems, wastewater, and decorative fountains.

[0070] Afew non-limiting illustrations of embodiments ofthis inventionincludethe following : 1) A method of potentiating the effectiveness ofabromine-basedmicrobiocide in combating formation of biofilm infestation and/or growth of biofilm on a surface, which method comprises contacting the biofilmor the surface onwhichbiofilminfests withan aqueous mediumto whichhave been added (a) a sulfamate-stabilized bromine chloride solution or (b) at least one 1, 3-dibromo-5,5-dialkylhydantoin in which each of the alkyl groups, independently, contains in the range of 1 to about 4 carbon atoms, the total number of carbon atoms in these two alkyl groups not exceeding 6, or both of (a) and (b), and (c) at least one biodispersant.

2) A method of potentiating the effectiveness of abromine-basedmicrobiocide whenin an aqueous mediumin contact with biofilm, orwhich comes into contactwithbiofilm, which method comprises providing in or adding to said aqueous medium a microbiocidally effective amount of (a) sulfamate-stabilized bromine chloride solution or (b) at least one 1,3- dibromo-5, 5-dialkylhydantoininwhicheachofthe alkylgroups, independently, contains in the range of 1 to about 4 carbon atoms, the totalnumber of carbonatoms inthesetwo alkyl groups not exceeding 6, or both of (a) and (b), and (c) at least one biodispersant.

3) Amethod of eradicating or atleast controllingbiofilmin contactwith anaqueous medium that is in contactwiththebiofilinorwhich comes into contact with the bio61tn, whichmethod comprises introducing into the aqueous medium: A) a bromine-based microbiocide comprising (a) a sulfamate-stabilized bromine chloride solution or (b) at least one 1, 3-dibromo-5, 5-dialkylhydantoin inwhich each of the alkyl groups, independently, contains in the range of 1 to about 4 carbon atoms, the total number of carbon atoms in these two alkyl groups not exceeding 6, or both of (a) and (b); and B) at least one biodispersant.

4) Amethod of eradicating or at least controlling biofilmin contact with an aqueous medium in contact with or which comes into contact with the biofilm, which method comprises introducing into the aqueous medium: A) abromine-basedmicrobiocidecomprising (i) an aqueous microbiocidalsolution comprised of one or more active bromine species, said species resulting from a reactioninwaterbetweenbromine, chlorine, or bromine chloride, or anytwo or all three thereof, and awater-soluble source ofsulfamate anion, (ii) at least one 1,3- dibrom-5, 5-dialkylhydantoin inwhich each ofthe alkyl groups, independently, contains in the range of 1 to about 4 carbon atoms, the total number of carbon atoms in these two alkyl groups not exceeding 6, or both of (i) and (ii); and B) at least one biodispersant that potentiates the effectiveness of said one or more active bromine species.

5) A composition which comprises: A) abromine-basedbiocide comprising (a) a sulfamate-stabilized bromine chloride solution or (b) at least one 1, 3-dibromo-5, 5-dialkylhydantoin in which each of the alkyl groups, independently, contains in. the range of 1 to about 4 carbon atoms, the total number of carbon atoms in these two alkyl groups not exceeding 6, or both of (a) and (b), and B) at least one biodispersant.

6) A method of any of 1), 2), 3), or 4), or a composition of 5) above wherein the bromine- based biocide used therein is a sulfamate-stabilized bromine chloride solution.

7) A method of any of 1), 2), 3), or 4), or a composition of 5) above wherein the bromine- based biocide used therein is at least one 1, 3-dibromo-5, 5-dialkyylhydantoininwhich each ofthe alkylgroups, independently, contains inthe range of 1 to about 4 carbon atoms, the total number of carbon atoms in these two alkyl groups not exceeding 6.

8) A method of any of 1), 2), 3), or 4), or a composition of 5) above wherein the bromine- based biocide used therein is 1, 3-dibromo-5, 5-dimethylhydantoin.

Still other embodiments are readily apparent from the foregoing description.

[0071] Componentsreferredto anywhereherein, whetherreferredtointhesingularorplural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical type (e. g. , another component, solvent, etc.). It matters not what chemical changes, transformations and/or reactions, ifany, takeplace in the resulting mixture or solution or formulation as such changes, transformations and/or reactions (e. g. , solvation, ionization, complex formation, or etc. ) are the natural result of bringing the specified reactants and/or components together under the conditions called for pursuant to this disclosure. Even though substances, components and ! oringredientsmaybereferredto inthepresenttense ("comprises","is", etc. ), the reference is to the substance, component or ingredient as it existed at the time just before it was first contacted, blended or mixedwith one or more other substances, components and/or ingredients in accordance with the present disclosure, and with the application of common sense.

[0072] Each and eveiypatent or otherpublicationreferredto in anyportion ofthis specification is inconporated in toto into this disclosure by reference, as if fully set forth herein. To the extent, if any, and only to the extent that the incorporated patent or publication is in conflict with the present description, the present description shall control.

[0073] This invention is susceptible to considerable variation in its practice. Therefore the foregoing description is not intendedto limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.