Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2003-06-03
2004-11-02
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S764000, C422S028000, C504S158000, C504S159000, C504S160000, C514S635000, C514S642000, C514S667000, C514S674000
Reexamination Certificate
active
06811711
ABSTRACT:
FIELD OF INVENTION
This invention relates to a method for inhibiting the growth of or killing microorganisms such as algae, bacteria, yeast and/or fungi in a recirculating water system, to treated recirculating water systems and to compositions and kits suitable for use in the method.
BACKGROUND OF THE INVENTION
The water in many industrial and recreational recirculating water systems such as cooling towers, swimming pools, spas, ornamental ponds, plumbing, pipework and other surfaces and the like is susceptible to infection by microorganisms such as bacteria, algae, yeast and fungi. These organisms may be pathogens or potential pathogens. Thus, for safety reasons, it is highly desirable to control their growth by the addition to the water of sanitizing agents. It is also desirable for aesthetic reasons, to control the growth of non-pathogenic bacteria, algae, yeast and fungi, particularly the so-called “nuisance” algae, yeast and fungi which cause discoloration and/or staining of the water and surfaces in contact with the water
A variety of sanitising agents have been employed for controlling undesirable micro-organisms in recreational recirculating water systems. The most common sanitising agents provide free chlorine and/or bromine (typically at a concentration in the water of 1 to 5 ppm free halogen). Chlorine may be provided either directly as chlorine gas or sodium or calcium hypochlorite or via a chlorine release agent such as a chlorinated isocyanurate or chlorinated and brominated hydantoin. Chlorine may also liberated in situ by electrolysis of sodium chloride. Other sanitising agents which have been used in such systems include ozone, ozone forming chemicals, hydrogen peroxide, hydrogen peroxide forming chemicals, copper and/or silver salts which provide copper, silver or chelated copper ions (typically at a concentration in the water of 0.1 to 1.0 ppm), quaternary amines and polymeric biguanides, especially poly(hexamethylene biguanide) (hereinafter referred to as PHMB) which is typically used at a concentration in recreational water of 6-10 ppm. Systems employing ultra violet light have also been used to sanitise recirculating water. Sanitising agents are used at higher concentrations in industrial recirculating water systems and additional sanitising agents may be used including but not limited to 2-methylisothiazolinone, 5-chloro-2-methylisothiazolinone, benzisothiazolinone, 2-bromo-2-nitropropane-1,3-diol, 1,2-dibromo-2,4-dicyanobutane, methylene bisthiocyanate, 2-(thiocyanomethylthio)-benzothiazole, formaldehyde and formaldehyde release agents, glutaraldehyde, dibromonitrilopropionamide and bromo-hydroxyacetophenone or mixtures thereof.
Although these primary sanitising agents are very effective in controlling bacteria they do not always provide consistent control of the so called “nuisance” algae, yeast and fungi which can cause discoloration and/or staining of the water and surfaces in contact with the water.
Examples of “nuisance” algae which are found in swimming pools include eukaryotic and prokaryotic algae, for example green algae (e.g.
Chlorella
spp.), black algae (e.g.
Phormidium
spp.) and mustard algae (e.g.
Eustigmatos
spp.). Of these, we have found that mustard algae are particularly difficult to control, regardless of the type of primary sanitising agent used. They appear as slimy deposits attached to the pool sides and bottom, as well as in the plumbing and in the filter, and vary in colour from dark green to brown.
Examples of “nuisance” fungi (often referred to as mold) isolated from swimming pools include
Aspergillus
spp.,
Cladosporium
spp., Mucor spp. and
Paecilomyces
spp.
Paecilomyces lilacinus
is the causative agent in so-called “water mold”, “pink mold” and “pink algae”.
P lilacinus
can manifest itself as white, grey or pink slimy deposits that are found in niches such as under ladder steps, in skimmer and pump baskets, in filters and piping.
P lilacinus
is also found growing in recirculating water filters where it can have an adverse effect on the efficiency and lifespan of the filter media. In its mature form, the fungus can also attach itself to pool surfaces and cause chronic turbidity problems which are difficult to control.
Examples of common “nuisance” yeasts found in swimming pools include
Saccharomyces
and
Candidia
species.
The wide spread occurrence of “nuisance” algae and fungi has lead to the introduction of methods of controlling these persistent microbes such as dosing with larger amounts of the sanitiser, shock dosing with chlorine or the introduction of further sanitisers or additives such as chelated copper, copper sulfate, combinations of chlorine and ammonium sulfate, colloidal silver, linear and/or cyclic quaternary amine compounds and polyquaternary amine compounds. However, these methods and algicides/fungicides have shown only limited efficacy against the “nuisance” algae and fungi and can give rise to undesirable levels of foam, especially in re-circulating water systems such as spas. Furthermore, in some circumstances, the additives themselves (especially chelated copper and copper sulphate) can cause staining of surfaces in contact with the water.
Any agent to be added to a recreational water system to control bacterial growth and “nuisance” algae, yeast and fungi must meet a number of demanding performance criteria. These include:
a) an excellent toxicology profile;
b) reasonable solubility;
c) freedom from unpleasant taste;
d) odourless or free from unpleasant odours (post addition);
e) non-staining of the construction materials e.g. plaster, plastic;
f) stability to light;
g) stability to other additives present in the water (e.g. sanitisers, H
2
O
2
and EDTA);
h) little or no effect on foaming; and
i) no adverse effect on water appearance e.g. discoloration or turbidity.
Thus, there is a need for a method of treating recirculating water systems to control not only the growth of pathogens, potential pathogens and other bacteria, but also the growth of those “nuisance” algae, yeast and/or fungi which persist in the presence of a primary sanitizing agent.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method for inhibiting the growth of or killing microorganisms, particularly bacteria, algae, yeast, and/or fungi in a recirculating water system comprising adding to the water a polymeric biguanide and an adjuvant of the Formula (1) or a salt thereof:
wherein:
R
1
is an optionally substituted C
8
to C
12
or C
18
to C
22
alkyl group; and
R
2
and R
3
each independently is H or optionally substituted C
1-4
-alkyl.
The Adjuvant
The alkyl group represented by R
1
may be a branched chain or more preferably a straight chain alkyl group. It is especially preferred that R
1
is n-octadecyl or more preferably n-dodecyl.
When any of R
2
and R
3
is C
1-4
-alkyl it may be a branched chain or more preferably a straight chain alkyl group. Examples of suitable alkyl groups include ethyl, n-propyl, iso-propyl and especially methyl. It is preferred however that R
2
and R
3
are H.
The alkyl groups represented by R
1
, R
2
and R
3
may be substituted by one or more substituents which do not adversely affect the activity of the adjuvant when used in combination with a polymeric biguanide according to the present invention. Suitable optional substituents include hydroxy, aryl (especially phenyl), amino, C
1-4
-alkoxy, hydroxy-C
1-4
-alkoxy or halogen (especially Cl). It is preferred, however that R
1
, R
2
and R
3
are un-substituted.
The adjuvant is preferably sufficiently water-soluble to give a concentration thereof in the recirculating water system which is sufficient to inhibit the growth of or kill microorganisms such as bacteria, algae, yeast, and/or fungi present in the recirculating water system. When the adjuvant is added to a recreational recirculating water system such as a swimming pool or spa it is also preferable that the adjuvant has sufficient water solubility not to adversely effect the appearance of the water in the recirculating water system, for
Unhoch Michael Joseph
Vore Roy Dean
Arch Chemicals Inc.
Hruskoci Peter A.
Morgan & Lewis & Bockius, LLP
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