CA2121622A1 - Process and composition for inhibiting microbial growth - Google Patents

Abstract

ABSTRACT

A microbial inhibiting composition and method is disclosed The composition comprises 2-(2-bromo-2-nitroethenyl) furan and (b) at least one additional biocidal component. The method comprises administering an amount of this combined treatment to the particular water containing system for which treatment is desired.

Description

21~1622 PROCESS AND COMPOSITION FOR INHIBITING
MICROBIAL GROWTH

FIELD OF THE INVENTION

This invention relates to compositions and methods for controlling . ~ -the growth of Trichoderma viride.
BACKGROUND OF THE INVENTION
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The formation of slimes by microorganisms is a problem that is encountered in many aqueous systems. For example, the problem is not 15 only found in natural waters such as lagoons, lakes, ponds, etc., and confined waters as in pools, but also in such industrial systems as cool-ing water systems, air washer systems and pulp and paper mill systems.
All possess conditions which are conducive to the growth and reproduc-tion of slime-forming microorganisms. In both once-through and recircu-20 lating cooling systems, for example, which employ large quantities ofwater as a cooling medium, the formation of slime by microorganisms is an extensive and constant problem.

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21216~2 Airborne organisms are readily entrained in the water from cooling towers and find this warm medium an ideal environment for growth and multiplication. Aerobic and heliotropic organisms flourish on the tower proper whila other organisms colonize and grow in such areas as the 5 tower sump and the piping and passages of the cooling system. The slime formation not only aids in the deterioration of the tower structure in the case of wooden towers, but also promotes corrosion when it deposits on metal surfaces. Slime carried through the cooling system plugs and fouls lines, valves, strainers, etc., and deposits on heat exchange sur-10 faces. In the latter case, the impedance of heat transfer can greatlyreduce the efficiency of the cooling system.

In pulp and paper mill systems, slime formed by microorganisms is commonly encountered and causes fouling, plugging, or corrosion of the 15 system. The slime also becomes entrained in the paper produced to cause breakouts on the paper machines, which results in work stoppages and the loss of production time. The slime is also responsible for un-sightly blemishes in the final product, which result in rejects and wasted output.
The previously discussed problems have resulted in the extensive utilization of biocides in cooling water and pulp and paper mill systems.
Materials which have enjoyed widespread use in such applications in-clude chlorine, chlorinated phenols, organo-bromines, and various or-25 gano-sulfur compounds. All of these compounds are generally useful for this purpose but each is attended by a variety of impediments. For ex-ample, chlorination is limited both by its specific toxicity for slime-forming organisms at aconomic levels and by the tendency of chlorine to react, which results in the expenditure of the chlorine before its full . : . ' . . -, ~ . , - .
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` 2~ ~6~2 biocidal function is achieved. Other biocides are attended by odor prob-lems and hazards with respect to storage, use or handling which limit their utility. To date, no one compound or type of compound has achieved a clearly established predominance with respect to the applica-5 tions discussed. Likewise, lagoons, ponds, lakes, and even pools, eitherused for pleasure purposes or used for industrial purposes for the dis-posal and storage of industrial wastes, become, during the warm weather, besieged by slime due to microorganism growth and reproduc-tion. In the case of industrial storage or disposal of industrial materials, 10 the microorganisms cause additional problems which must be eliminated prior to the materials' use or disposal of the waste.

Naturally, economy is a major consideration with respect to all of these biocides. Such economic considerations attach to both the cost of 15 the biocide and the expense of its application. The cost performance index of any biocide is derived from the basic cost of the material, its effectiveness per unit of weight, the duration of its biocidal or biostatic effect in the system treated, and the ease and frequency of its addition to the system treated. To date, none of the commercially available biocides 20 has exhibited a prolonged biocidal effect. Instead, their effectiveness is rapidly reduced as a result of exposure to physical conditions such as temperature, association with ingredients contained by the system toward which they exhibit an affinity or substantivity, etc., with a resultant restric-tion or elimination of their biocidal effectiveness, or by dilution.

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2~2~622 As a consequence, the use of such biocides involves their con-tinuous or frequent addition to the systems to be treated and their addi-tion to multiple points or zones in the systems to be treated. Accordingly, the cost of the biocide and the labor cost of applying it are considerable.
5 In other instances, the difficulty of access to the zone in which slime for-mation is 0xperienced precludes the effective use of a biocide. For ex-ample, if in a particular system there is no access to an area at which slime formation occurs the biocide can only be applied at a point which is upstream in the flow system. However, the physical or chemical condi-10 tions, e.g., chemical reactivity, thermal degradation, etc., which existbetween the point at which the biocide may be added to the system and the point at which its biocidal effect is desired render the effective use of a biocide impossible.

Similarly, in a system experiencing relatively slow flow, such as a paper mill, if a biocide is added at the beginning of the system, its bioci-dal effect may be completely dissipated before it has reached all of the points at which this effect is desired or required. As a consequence, the biocide must be added at multiple points, and even then a diminishing 20 biocidal effect will be experienced between one point of addition to the system and the next point downstream at which the biocides may be added. In addition to the increased cost of utilizing and maintaining mul-tiple feed points, gross ineconomies with respect to the cost of the biocide are experienced. Specifically, at each point of addition, an ex-25 cess of the biocide is added to the system in order to compensate for thatportion of the biocide which will be expended in reacting with other con-stituents present in the system or experience physical changes which impair its biocidal activity.

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~,, " 21216~2 SUMMARY OF THE INVENTION

The present inventors have discovered that a composition of 2-(2-bromo-2-nitroethenyl) furan (BNEF) and another biocidal component is effective as a biocide directed towards controlling Trichoderma viride.

DESCRIPTION OF THE RELATED ART

U.S. Patent No. 5,158,972, Whitekettle et al., teaches the use of 2-(2-bromo-2-nitroethenyl) furan and glutaraldehyde to control the growth of Klebsiella r neumoniae. U.S. Pat. No. 4,965,377, McCoy et al., teaches a method for forming 2-(2-bromo-2-nitroethenyl) furan which proved effec-tive as an antimicrobial agent.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to compositions and methods for controlling the growth of fungi comprising a synergistic mixture of (a) 2- ~ ;
(2-bromo-2-nitroethenyl) furan (BNEF) and (b) at least one additional component selected from:

(1 ) Dodecylguanadine hydrochloride (DGH), or (2) Diiodomethyl-p-tolylsulfone (DMTS).

The present inventors have found these combinations particularly effective against the Trichoderma viride species which is a common fungal nuisance found in industrial cooling waters and pulping and papermaking systems.

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21~ 622 This particular species of mold is a member of the Fungi Imperfecti which reproduce by means of asexual spores or fragmentation of myce-lium. It is commonly found on fallen timber and is a widely occurring soil organism. Because of its ubiquitous nature, this mold continually con-taminates open cooling systems and pulping and papermaking systems.
Contamination can take the form of airborne spores or fungal mats - a mass of agglomerated hyphae bound together with bacterial cells and cemented by gelatinous polysaccharide or proteinaceous material. The slimy mass entraps other detritus, restricts water flow and heat transfer and may serve as a site for corrosion.

These fungi are able to grow in environments hostile to other life-forms. While they are strict aerobes, Trichoderma produce both hyphae, the vegetative structure, and spores which require minimal metabolic turnover and are able to withstand harsher environmental conditions.
Accordingly, by reason of demonstrated efficacy in the growth inhibition of this particular species, one can expect similar growth inhibition attrib-utes when other fungi are encountered. It is also expected that these compositions will exhibit similar srowth inhibition attributes when bacterial andalgal speciesareencountered. ~:

In accordance with the present invention, the combined treatment may be added to the desired aqueous system in need of biocidal treat-ment, in an amount of from about 0.1 to about 200 parts of the combined 25 treatment of BNEF and DGH to one million parts (by weight) of the aque-ous medium. Preferably, about 5 to about 50 parts of the combined treatment of BNEF and DGH per one million parts (by wei~ht) of the aqueous medium is added. The BNEF and DMTS may be added in an amount of frorn about 1 to about 500 parts per million parts (by weight) of 30 the aqueous medium.

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,' ' ,: . , i'~X, ' -`` 212~6~2 The combined treatment is added, for example, to cooling water systems, paper and pulp mill systems, pools, ponds, lagoons, lakes, etc., to control the formation of fungal microorganisms, which may be con-tained by, or which may become entrained in, the system to be treated. It 5 has been found that the compositions and methods of utilization of the treatment are efficacious in controlling the fungal organism, Trichoderma viride, which may populate these systems. It is thought that the com-bined treatment composition and method of the present invention will also be efficacious in inhibiting and controlling all types of aerobic microorgan-1 0 isms.

Surprisingly, it has been found that when the ingredients aremixed, in certain instances, the resulting mixtures possess a higher de-gree of fungicidal activity than that of the individual ingredients compris-15 ing the mixture. Accordingly, it is possible to produce a highly efficaciousbiocide. Because of the enhanced activity of the mixture, the total quantity of the biocidal treatment may be reduced. In addition, the high degree of biocidal effectiveness which is provided by each of the ingredi-ents may be exploited without use of higher concentrations of each.
The following experimental data were developed. It is to be remembered that the following examples are to be regarded solely as being illustrative and not as restricting the scope of the invention.

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2~ 2~622 DESCRIPTION OF THE PREFERRED EMBODIMENT

The combined treatments were added in varying ratios and over a wide range of concentrations to a iiquid nutrient medium which was sub-5 sequently inoculated with a standard volume of a suspension of sporesfrom Trichoderma viride. Growth was measured by determining the amount of radioactivity accumulated by the cells when 14C-glucose was added as the sole source of carbon in the nutrient medium. The effect of the biocide chemicals, alone and in combination, is to reduce the rate 10 and amount of 14C incorporation into the cells during incubation, as compared to controls not treated with the chemicals. Additions of the biocides, alone and in varying combinations and concentrations, were made according to the accepted "checkerboard" technique described by M.T. Kelley and J. M. Matsen, Antimicrobial A~ents and ChemotheraPv.
15 9:440 (1976). Following a two hour incubation, the amount of radioactiY-ity incorporated in the cells was determined by counting (1 4C liquid scin-tillation procedures) for all treated and untreated samples. The percent reduction of each treated sample was calculated from the relationship: :

20 Cont!ol 14C!cPm) - Treated 14C(cpm) x 100 = % reduction Control 14C(cpm) Plotting the % reduction of 14C level against the concentration of each biocide acting alone results in a dose-response curve, from which 25 the biocide dose necessary to achieve any given % reduction can be interpolated.

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~` 2121622 g Synergism was determined by the method of calculation described by F.C. Kull, P.C. Eisman, H.D. Sylwestrowicz and R.L. Mayer, APPlied Microbioloqv, 9,538 (1961) using the relationship:

QA QB
--+--= synergism index (Sl) ~ ~;

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Qa = quantity of compound A, acting alone, producing an end point Qb = quantity of compound B, acting alone, producing an end point QA = quantity of compound A in mixture, producing an end point QB = quantity of compound B in mixture, producing an end point The end point used in the calculations is the % reduction caused by each mixture of A and B. QA and QB are the individual concentrations in the A/B mixture causing a given % reduction. Qa and Qb are deter~
mined by interpolation from the respective dose response curves of A
and B as those concentrations of A and B acting alone which produce the . ~:same % reduction as each specific mixture produced.

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Dose-response curves for each active acting alone were deter-mined by linear regression analysis of the dose-response data. Data were fitted to a curve represented by the equation shown with each data set. After linearizing the data, the contributions of each biocide compo-5 nent in the biocide mixtures to the inhibition of radioisotope uptake weredetermined by interpolation with the dose-response curve of the respec-tive biocide. If, for example, quantities f QA plus QB are sufficient to give a 50% reduction in 1 4C content, Qa and Qb are those quantities of A are B acting alone, respectively, found to give 50% reduction in 1 4C
10 content. A synergism index (Sl) is calculated for each combination of A
and B.

Where the Sl is less than 1, synergism exists. Where the Sl=1, additivity exists. Where Sl is greater than 1, antagonism exists.
The data in the following tables come from treating Trichoderma viride, a common nuisance fungal ~ype found in industrial cooling waters and in pulping and papermaking systems, with varying ratios and concen-trations of BNEF and DGH. Shown for each combination is the % reduc-20 tion of 14C content (% I), the calculated Sl, and the weight ratio of BNEFand DGH.

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DGH vs. BNEF ~ .
ppm ppm Ratio DGH1 BNEF2 DGH:BNEF %I Sl 2.5 0 100:0 91 1.25 0 100:0 83 0.63 0 100:0 38 0.31 0 100:0 0 0.16 0 100:0 0 0.04 0 100:0 0 0 40 0:100 89 0 20 0:100 81 0 5 0:100 55 0 1.25 0:100 12 0 0.63 0:100 0 0. 31 0:100 0 2.5 40 1:16 98 1.99 2.5 20 1:8 98 1.61 2.5 5 1:2 96 1.34 2.5 1.25 2:1 95 1.28 2.5 0.63 4:1 95 1.27 2.5 0.31 8:1 94 1.27 , ,, 2 ~ 2 ~ ~22 , TABLE I (Cont'd) DGH vs. BNEF
ppm ppm Ratio 5 DGH1 BNEF2 DGH.BNEF %I Sl 1.25 40 1 :32 97 1.44 1.25 20 1:16 96 1.05 1.25 5 1 :4 93 0.76 10 1.25 1.25 1: 1 91 0.68 1.25 0.63 2: 1 91 0.67 1.25 0.31 4:1 90 0.66 0.63 40 1 :64 95 1.25 0.63 20 1 :32 91 0.87~
15 0.63 5 1:8 84 054b 0.63 1.25 1 :2 79 0.43 0.63 0.63 1: 1 73 0.44 0.63 0.31 2:1 60 0.52*
0.31 40 1:129 91 1.28 20 0.31 20 1 :65 82 1.02 0.31 5 1:16 62 0.79 0.31 1.25 1 :4 42 0.68 0.31 0.63 1 :2 39 0.56 0.31 0.31 1:1 21 0.83 17~
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TABLE I (Cont'd) :
DGH vs. BNEF :- ~
ppm ppm Ratio -DGH1 BNEF2 DGH:BNEF %I Sl 0.16 40 1:250 91 1.18 0.16 20 1:125 84 0.87 0.16 5 1:31 69 0.51 0.16 1.25 1 :8 37 0.64 0.16 0.63 1:4 29 0.55 0.16 0.31 1:2 22 0.52 0.04 40 1:1000 88 1.29 0.04 20 1 :500 81 0.93~
0.04 5 1:125 59 0.66~ :
0.04 1.25 1:31 12 1.59 0.04 0.63 1 :16 9 0.99 :
0.04 0.31 1 :8 0 1.02 - : ~ -TABLE ll DGH vs. BNEF
ppm ppm Ratio DGH1 BNEF2 DGH:BNEF %I Sl 2.5 0 100:0 91 1.25 0 100:0 66 0.63 0 100:0 19 0.31 0 100:0 0 .. ,. . , , . :

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ppm ppm Ratio 5 DGH1 BNEF2 DGH:BNEF %i Sl 0.16 0 100:0 0 0.04 0 100:0 0 0 40 0: 100 90 10 0 20 0: 100 85 0 5 0: 100 53 0 1.25 0:100 16 0 0.63 0:100 11 0 0.31 0:100 0 15 2.5 40 1:16 98 1.88 2.5 20 1 :8 98 1.46 2.5 5 1:2 97 1.17 2.5 1.25 2:1 96 1.10 2.5 0.63 4:1 95 1.10 20 2.5 0.31 8:1 94 1.10 1.25 40 1 :32 98 1.39 1.25 20 1:16 97 0.98 1.25 5 1 :4 93 0.68*
1.25 1.25 1: 1 82 0.68*
25 1.25 0.63 2:1 85 0.63*
1.25 0.31 4:1 89 0.58*

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`- 2121 ~22 ' TABLE !l (cont'd) DGH vs. BNEF
ppm ppm Ratio 5 pGH1 BNEF2 DGH:BNEF %I Sl 0.63 40 1 :64 94 1.28 0.63 20 1 :32 91 0.87*
0.63 5 1 :8 81 0.55*
0.63 1.25 1:2 63 0.55*
0.63 0.63 1 :1 56 0.54*
0.63 0.31 2:1 51 0.54*
0.31 40 1:129 94 1.19 0.31 20 1 :65 89 0.80*
0.31 5 1:16 76 0.47*
0.31 1.25 1 :4 28 1.19 0.31 0.63 1 :2 25 0.92*
0.31 0.31 1:1 26 0.65*
0.16 40 1:250 93 1.12 0.16 20 1:125 88 0.77*
0.16 5 1:31 73 0.45*
0.16 1.25 1:8 34 0.82*
0.16 0.63 1:4 22 0.77*
0.16 0.31 1:2 23 0.49*
0.04 40 1:1000 92 1.15 0.04 20 1 :500 87 0.73*
0.04 5 1:125 53 1.00 0.04 1.25 1:31 19 1.36 0.04 0.63 1:16 12 0.96 0.04 0.31 1 :8 9 0.62 :` 212~2 Asterisks in the Sl column indicate synergistic combinations in accordance with the Kull method supra, while:

indicates a product with 33% actives D~H and 2 indicates a product with 10% actives BNEF

In Tables I and ll, differences seen between the replicates are due to normal experimental variance.

In accordance with Tables l-ll supra., unexpected results occurred more frequently within the product ratios of DGH to BNEF of from about 4:1 to 1:500. Since the DGH product contains about 33% active biocidal component, and the BNEF product contains about 10% active biocidal component, when based on the active biocidal component, unexpected results appear more frequently within the range of active component of DGH:BNEF of about 13:1 to 1:150. At present, it is most preferred that any comm0rcial product embodying the invention comprises a weight ratio of active component of about 1:1 DGH:BNEF.

The data in the following tables come from treating Trichoderma viride, a common nuisance fungal type found in industrial cooling waters and in pulping and papermaking systems, with varying ratios and concen-trations of BNEF and DMTS. Shown for eacl1 combination is the % re-duction of 14C content (%I), the calculated Sl, and the weight ratio of BI~IE~ and DMTS.

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TABLE lll DMTS vs. BNEF
ppm ppm Ratio DMTS BNEF DMTS:BNEF %l Sl 6 0 100:0 96 3 0 100:0 93 1.5 0 100:0 90 0.75 0 100:0 77 0.38 0 100:0 60 0.19 0 100:0 54 0 40 0: 100 91 0 20 0: 100 83 0 5 0:100 71 0 2.5 0:100 62 0 1.25 0: 100 52 0 0.63 0: 100 38 6 40 1:6.7 98 2.14 6 20 1 :3.3 97 1.86 6 5 1.2:1 96 1.64 6 2.5 2.4:1 96 1.65 6 1.25 4.8:1 96 1.66 6 0.63 9.5:1 96 1.62 3 40 1:13.3 92 2.21 3 20 1 :6.7 94 1.44 3 5 1:1.7 93 1.11 3 2.5 1.2:1 94 0.97 3 1.25 2.4:1 93 1.04 3 0.63 4.8: 1 94 0.96 ~.:

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-` 2~2~6~2 TABLE lll (Cont'd) DMTS vs. BNEF
ppm ppm Ratio 5 DMTS BNEF DMTS:BNEF %I Sl 1.5 40 1 :26.7 86 2.64 1.5 20 1:13.3 89 1.38 1.5 5 1 :3.3 92 069*
1.5 2.5 1: 1.7 91 0.65*
1.5 1.25 1.2:1 89 0.70*
1.5 0.63 2.4: 1 40 0.66*
0.75 40 1 :53.3 94 1.12 0.75 20 1 :26.7 91 0.86*
0.75 5 1 :6.7 85 0.66*
0.75 2.5 1 :3.3 83 0.65*
0.75 1.25 1:1.7 80 0.74*
0.75 0.63 1.2:1 77 0.83*
0.38 40 1:105.3 94 1.06 0.38 20 1 :52.6 91 0.74*
0.38 5 1:13.2 81 0.63*
0.38 2.5 1 :6.6 78 0.57~
0.38 1.25 1 :3.3 71 0.79*
0.38 0.63 1:1.7 61 1.41 0.19 40 1:210.5 91 1.25 0.19 20 1:105.3 88 0.82 0.19 5 1:26.3 78 0.60 0.19 2.5 1:13.2 69 0.78 0.19 1.25 1 :6.6 61 1.01 0.19 0.63 1:3.3 54 1.34 , ..

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TABLE IV
DMTS vs. BNEF
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t~; ppm ppm Ratio DMTS BNEF DMTS:BNEF %l Sl 6 0 100:0 95 3 0 100:0 92 1.5 0 100:0 88 0.75 0 100:0 79 0.38 0 100:0 58 0.19 0 100:0 34 0 40 0: 100 86 0 20 0: 100 76 ~- 15 0 5 0:100 54 0 2.5 0:100 38 0 1.25 0: 100 29 0 0.63 0:100 17 6 40 1 :6.7 97 2.31 6 20 1 :3.3 95 2.32 6 5 1.2:1 96 1.95 6 2.5 2.4:1 96 1 96 6 1.25 4.8:1 95 1 98 6 0.63 9.5:1 95 1.96 3 40 1:13.3 97 1.46 3 20 1 :6.7 96 1.24 3 5 1:1.7 95 1 07 3 2.5 1.2:1 94 1 07 3 1.25 2.4:1 94 1 07 3 0.63 4.8:1 94 1 07 ~, ,;.

2~21 622 TABLE IV (Cont'd) DMTS vs. BNEF
ppm ppm Ratio ~: I5 DMTS BNEF DMTS:BNEF %I Sl 1.5 40 1 :26.7 96 1.07 1.5 20 1:13.3 94 0.84 1.5 5 1 :3.3 92 0.68~
1.5 2.5 1:1.7 91 0.65~ -1.5 1.25 1.2:1 89 0.69 1.5 0.63 2.4:1 88 0.72 0.75 40 1 :53.3 g4 0.93 0.75 20 1 :26.7 93 0.64 0.75 5 1 :6.7 85 0.54~
0.75 2.5 1 :3.3 81 0.60*
0.75 1.25 1 :1.7 80 0.57 0.75 0.63 1.2:1 81 0.52 0.38 40 1:105.3 93 0.84 0.38 20 1 :52.6 89 0.60 0.38 5 1:13.2 77 0.54 0.38 2.5 1 :6.6 62 0.93 0.38 1.25 1 :3.3 51 1.43 0.38 0.63 1:1.7 63 0.79 0.19 40 1:210.5 93 0.78 0.19 20 1:105.3 86 0.63 0.19 5 1:26.3 75 0.43 0.19 2.5 1:13.2 54 0.94 0.19 1.25 1:6.6 46 1.12 0.19 0.63 1:3.3 41 1.21 ,. . . "
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2~2~ 6~2 Asterisks in the Sl column indicate synergistic combinations in accordance with the Kull method supra.
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In Tables lll and IV, differences seen between the replicates are 5 due to normal experimental variance.

In accordance with Tables III-IV supra., unexpected results occurr-ed more frequently within the product ratios of DMTS to BNEF of from about 2.4:1 to about 1:105.3 as 100% actives. Since the DMTS product 10 contains 40% active biocidal component and the BNEF product contains 10% active biocidal component, unexpected results appear more fre-~uently within the range of active component (100% actives basis) of DMTS:BNEF of about 9.6:1 to about 1:26.3. At present, the most pre-ferred ratio comprises a weight ratio of active component of about 1:1 15 DMTS:BNEF.
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While this invention has been described with respect to particular embodirrlents thereof, it is apparent that numerous other forms and modi-fications of this invention will be obvious to those skilled in the art. The 20 appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of ~he present invention.

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Claims (9)

1. A fungal inhibiting composition comprising a synergistic mixture of (a) 2-(2-bromo-2-nitroethenyl) furan and (b) at least one addi-tional biocidal component selected from:

Dodecylguanadine hydrochloride, and Diiodomethyl-p-tolylsulfone.

2. The composition as claimed in claim 1 wherein the weight ratio of (a) to dodecylguanadine hydrochloride is from about 150:1 to 1:13.

3. The composition as claimed in claim 1 wherein the weight ratio of (a) to diiodomethyl-p-tolylsulfone is from about 26.3:1 to 1:9.6.

4. A method for controlling the growth of fungi in an aqueous system which comprises adding to said system a synergistically effective amount for the purpose of a composition comprising (a) 2-(2-bromo-2-nitroethenyl) furan and (b) at least one additional biocidal component selected from:

Dodecylguanadine hydrochloride, and Diiodomethyl-p-tolylsulfone.

5. The method as claimed in claim 4 wherein said fungi are Trichoderma viride.

6. The method as claimed in claim 4 wherein (a) and dodecyl-guanadine hydrochloride are added to said system in an amount from about 0.1 to about 200 parts per million of said system.

7. The method as claimed in claim 4 wherein (a) and diiodomethyl-p-tolylsulfone are added to said system in an amount from about 1 to about 500 parts per million of said system.

8. The method as claimed in claim 4 wherein said aqueous system comprises a cooling water system.

9. The method as claimed in claim 4 wherein said aqueous system comprises a pulping and papermaking system.