Method for controlling zebra mussels in ship ballast tanks

A method for controlling zebra mussels in ship ballast tanks comprising treating ballast water which contains zebra mussels or which is prone to zebra mussel infestation with an effective amount of a didecyl dimethyl ammonium halide. A preferred compound is a didecyl dimethyl ammonium chloride.

BACKGROUND OF THE INVENTION 
The present invention relates to the control of zebra mussels (Dreissena 
polymorpha) in ballast tanks by utilizing as a molluscicide an effective 
amount of a didecyl dimethyl ammonium halide. 
Water is oftentimes used as ballast in ships to provide stability. In 
general, the ballast water lowers the ship's center of gravity to a 
desired level when there isn't cargo on board which would provide the same 
effect. If ballast water is drawn into a ship's ballast tanks from zebra 
mussel-infested water, it can infest the body of water into which it is 
discharged. There is therefore a strong need in the art to control zebra 
mussels in ballast water. 
Zebra mussels recently have been discovered in the Great Lakes. It is 
believed that these mollusks were carried to North America in the ballast 
of ships from Europe. Zebra mussels reproduce quickly, and attach to 
virtually any hard surface in contact with an aqueous system in which they 
are present. These organisms are particularly troublesome to industrial 
and municipal users of fresh water, as zebra mussels can quickly foul 
water intakes and process equipment. 
Zebra mussels fall within the class Bivalvia of the phylum Mollusca. The 
mature mussels are characterized by threadlike tenacles (byssal threads) 
which enable them to attach themselves to virtually any hard underwater 
surface. Since a zebra mussel is particularly adherent to the shell of 
another zebra mussel, these mollusks tend to "stack up", one upon another, 
so that they can completely clog intake orifices. Additionally, the 
threads enable the mussels to affix themselves to a surface which is 
positioned in any plane relative to horizontal. Thus, unlike other 
mollusks such as Asian clams (Corbicula), zebra mussels are found on the 
ceilings, vertical surfaces and floors of under water equipment. 
On a daily basis, vast quantities of water are removed from rivers, lakes 
and streams for potable water use and for use in a variety of industrial 
processes. The greatest industrial use of water is for cooling purposes, 
and the greatest nonconsumptive industrial demand for water as a heat 
transfer medium comes from the steam-electric generating industry. Also, 
municipalities draw water for public consumption. 
Source water supports an abundance of biological life forms, many of which 
cannot be removed from the water before it is used. While some of these 
biological life forms may not adversely affect municipal or industrial 
treatment processes, zebra mussels are biofouling organisms which have 
become a severe problem in North America in a very short time. These 
mussels foul intake piping and equipment surfaces in municipal water 
treatment plants and in industrial water systems. 
It is believed that zebra mussels did not become prevalent in Lake Erie 
until late 1988 or 1989. They are now rapidly spreading into Lake Michigan 
and into the rivers of the Midwest and Northeast. In a relatively short 
time, they can reach population densities in excess of 30,000 mussels per 
square meter. For this reason, zebra mussels can completely shutdown 
municipal and industrial systems which rely on fresh water infested with 
zebra mussels. It is believed that zebra mussel fouling will eventually 
threaten virtually every domestic municipal, utility and industrial user 
of fresh water that draws its supply from a source which is in fluid 
communication with the Great Lakes. 
Zebra mussel fouling of such equipment as intake piping and steam 
condensers can be extremely troublesome. Immature or small mussels are 
easily drawn through intake screens. Once inside a system, they can lodge 
anywhere. The problem is made worse by the fact that, in the larval state, 
zebra mussels are carried by flowing water throughout treatment and/or 
process systems. 
DISCUSSION OF RELEVANT ART 
In Europe, it is common to utilize dual intake systems to handle zebra 
mussel problems, so that one system can be mechanically cleaned while the 
other is in operation, or to draw source water from depths where the 
maximum water temperature is too cold (below about 13.degree. C.) for 
zebra mussels to reproduce. The treatment of ballast water, however, is 
not known in the art. The instant method for controlling zebra mussels in 
ballast water is therefore a novel chemical treatment method. In this 
method, a didecyl dimethyl ammonium halide is added to zebra-infested 
water in a ship's ballast tank, thereby controlling and/or killing the 
zebra mussels prior to discharge of the ballast water. 
Chemical agents for controlling zebra mussels, including chlorine and other 
oxidizing agents, have been used. However, chlorine is not desirable for 
environmental reasons. 
U.S. Pat. No. 4,462,914 to Smith discloses the use of polyquats such as 
dimethyl diallyl ammonium chloride polymers to control Asian clams 
(Corbicula). However, this patent is silent regarding the efficacy of 
didecyl dimethyl ammonium halides as agents to control zebra mussels, and 
the use of the same to treat ballast water. 
It is also noteworthy that dialkyl diallyl ammonium polymers are widely 
used in municipal and industrial water treatment. For example, dimethyl 
diallyl ammonium chloride polymers are added as clarification aids to the 
water intakes of municipal potable water plants. To the best of the 
inventor's knowledge, however, didecyl dimethyl ammonium halides have not 
been added to control zebra mussel growth or fouling in ballast waters. 
Additionally, polyquaternary compounds have been utilized for control of 
microorganisms such as bacteria, fungi, and algae in aqueous systems. See, 
e.g., U.S. Pat. Nos. 4,113,709 and 4,111,679. Simple quaternary ammonium 
compounds have been used to control fouling by microorganisms and 
molluscs. See, e.g., Nashimura et al., Japan Kokai No. 74 81,535 (1974); 
Roth, German Offenlegungsschrift No. 2,642,606; and Sindery, French Pat. 
No. 1,460,037. 
Ramsey et al, "Effects of Nonoxidizing Biocides on adult Corbicula 
fluminea" (1988), disclose the application of various biocides, including 
dodecylguanidine hydrochloride (DGH), benzalkonium chloride, pyridinium 
chloride, dioctyl dimethyl ammonium chloride, 
poly[oxyethylene(dimethylimino)-ethylene (dimethylimino)-ethylene 
dichloride], glutaraldehyde, 2,2-dibromo-3-nitrilo propionamide, 
N-4-dihydroxy-.alpha.-oxobenzene ethanimidoyl chloride, 
5-chloro-2-methyl-4-isothiazolin-3-one/2-methyl-4-isothiazolin-3-one, 
N-[(.alpha.)-(1-nitroethyl) benzyl]ethylenediamine and 
2-(tert-butylamino)-4-chloro-6(ethylamine)-5-triazine, for the purpose of 
controlling Asian clams. It is noted that dioctyl dimethyl ammonium 
chloride is shown not to be effective for this purpose, and that the 
addition of these additives to ballast waters is not known or suggested. 
U.S. Pat. No. 4,816,163, to Lyons et al, discloses the use of water-soluble 
alkyl guanidine salts, alone or in combination with methylene 
bis-thiocyanate or alkyl dimethyl benzyl ammonium chloride, to control the 
biofouling of macroinvertebrates, particularly Corbicula. At column 2, 
lines 18-20, the '163 patent states that: "Another fresh water mollusk, 
Dreissna -- the zebra mussel, causes fouling problems in Europe to cooling 
systems in a similar manner as the Asiatic Clam." The inventor notes, 
however, that Asiatic clams do not rapidly adhere to hard surfaces, 
instead remaining in areas where silt deposits are present. Thus, Asiatic 
clams do not coat underwater vertical or "ceiling" surfaces, as do zebra 
mussels. Also, Asian clams tend to move around in silt and mud, while 
zebra mussels are generally sessile once their byssal threads attach, and 
Corbicula are hermaphroditic, while zebra mussels rely on external 
fertilization. 
Copending U.S. patent applications Ser. Nos. 511,156 and 510,495 relate to 
the use of polyquats, particularly polyDMDAAC's, and didecyl dimethyl 
ammonium halides, individually, to control zebra mussel growth. Copending 
U.S. patent application Ser. No. 594,451 relates to the use of these 
components, in combination, to control zebra mussels. None of these 
applications, however, disclose the novel treatment step of applying the 
molluscide to ballast waters. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a method for 
inhibiting the growth of zebra mussels in ballast waters, and therefore in 
waters into which ballast water is discharged, and a method for 
controlling fouling caused by zebra mussels in ballast tanks. These 
methods comprise adding an effective amount for the purpose, preferably a 
molluscicidally effective amount, of a didecyl dimethyl ammonium halide to 
ballast water which contains zebra mussels and/or zebra mussel larvae or 
which is prone to zebra mussel infestation.

DETAILED DESCRIPTION OF THE INVENTION 
The instant invention is directed to a method for controlling the growth of 
zebra mussels in ballast water which contains or is prone to infestation 
by zebra mussels, comprising adding to such a water an effective amount 
for the purpose of a didecyl dimethyl ammonium halide. The most preferred 
compound is didecyl dimethyl ammonium chloride. 
A didecyl dimethyl ammonium chloride product is commercially available from 
Calgon Corporation as H--130. Also, a 50% active, by weight, didecyl 
dimethyl ammonium chloride is commercially available from Lonza as 
BARDAC.RTM. 2250. This product also contains 10%, by weight, ethanol and 
40%, by weight, water. 
The expression "controlling the growth of zebra mussels", as used herein, 
is intended to cover killing, inhibiting the growth of, or preventing the 
growth of, zebra mussels. In a similar manner, the expression 
"molluscicidally effective amount" as used herein means an amount which 
kills, inhibits the growth of, or prevents the growth of zebra mussels in 
the aqueous systems where the molluscicide is employed. 
"Effective amount", as used herein, refers to that amount of compound 
necessary to accomplish the purpose of the treatment. The effective amount 
of didecyl dimethyl ammonium halide necessary in the methods of the 
present invention may vary due to such factors as the ambient temperature 
of the ballast water being treated, the presence of substances in the 
water which bind to or otherwise inactivate cationic compounds (for 
example, silt), the concentration and predominant stage of life cycle of 
the zebra mussels present in the aqueous system to be controlled, the 
particular didecyl dimethyl ammonium halide which is employed and other 
factors. Generally, however, an effective amount will be in the range of 
from about 0.1 to about 2000 parts per million, preferably about 1 to 
about 100, and most preferably about 5 to 50 parts per million, based on 
total weight of active compound added and the total weight of the water in 
the ballast system being treated. 
It is noteworthy that ballast systems may have a "turbidity demand" for 
cationic compounds. Thus, cationic compounds interact with and are 
"tied-up" by solids which cause turbidity. The portion of cationic 
compound "tied-up" by sources of turbidity, such as silt, is believed to 
be ineffective relative to zebra mussels. For this reason, sufficient 
compound must be fed to both account for the turbidity demand of the 
system being treated and to control zebra mussels. A preferred method 
therefore comprises: a) determining the turbidity level of the ballast 
system to be treated and the corresponding turbidity demand for the 
particular compound being fed; b) feeding sufficient compound to react 
with and tie-up the turbidity present, i.e., to account for the turbidity 
demand of the ballast system by tieing-up existing turbidity; and c) 
feeding an effective amount of compound to control zebra mussels. 
Preferably, feed steps b) and c) can be carried out simultaneously. Step 
a) involves routine procedures well within the skill of a water-treatment 
practitioner. Ideally, the instant compounds are added to the ballast 
water to be treated as soon as possible after the ballast water enters the 
ballast tanks. This maximizes the time available for these compounds to 
act on the zebra mussels. Minimally, sufficient residence time should be 
allowed so as to allow for adequate control of zebra mussels. 
The inventor also notes that veligers, which are free-floating planktonic 
immature zebra mussels or larva, are produced when water temperatures 
exceed about 13.degree. C. Peak densities occur between about 20.degree. 
and 22.degree. C., and temperatures in excess of about 37.degree. C. 
greatly depress veliger development. In most of the United States, zebra 
mussel reproduction is seasonal. 
Thus between the periods when ballast water temperatures rise to about 
13.degree. C. (generally in the spring) and fall to below about 13.degree. 
C. (generally in the autumn) zebra mussels must be treated. It is believed 
that the instant didecyl dimethyl ammonium halides react with the gills of 
zebra mussels to effectively suffocate the mussels, though the inventor 
does not wish to be bound by this mechanism. 
Aside from controlling the growth of zebra mussels, the instant invention 
further relates to a method for controlling the fouling potential of zebra 
mussels (biofouling caused by zebra mussels) in ballast tanks comprising 
adding an effective amount of a didecyl dimethyl ammonium halide to 
ballast water containing zebra mussels or prone to zebra mussel 
infestation. Ballast systems which are prone to zebra mussel infestation 
include those wherein ballast water is drawn from a fresh water system 
which contains zebra mussels. 
The cationic compounds employed in the instant methods can be added to the 
ballast system being treated in any conventional manner and at any point 
suited to provide ready dissolution and rapid distribution of the compound 
to all points in the ballast system being treated. Various formulations of 
the cationic compounds which facilitate their dissolution in water may be 
prepared in accordance with known methods. Also, other water treatment 
agents can be added to the system being treated in conjunction with the 
instant polymers. For example, other biocides, surfactants, scale or 
corrosion inhibitors, etc. can be used with the instant polymers, absent 
compatability problems. 
The efficacy of didecyl dimethyl ammonium chloride relative to controlling 
zebra mussels is demonstrated by the following examples. 
EXAMPLES 1-6 
Static Renewal Tests 
Various concentrations of didecyl dimethyl ammonium chloride were 
established in beakers containing 100 ml of heavily aerated tap water. Ten 
adult zebra mussels from Lake Erie (Dreissena polymorpha), each between 2 
mm and 10 mm in shell length, were added to each of the test beakers, as 
well as to two (2) control beakers containing only heavily aerated tap 
water. The water was changed daily throughout the test period. Only 
mussels which were definitely alive (feeding) were used in the test. The 
zebra mussels were observed daily for signs of life and the results 
obtained are set forth in the table below. 
TABLE 1 
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STATIC RENEWAL BIOASSAY TEST RESULTS 
Example Conc. (mg/L 
Number of Organisms Alive 
Number 
Inhibitor 
Prod.) 0 Hrs. 
24 Hrs. 
48 Hrs. 
72 Hrs. 
96 Hrs. 
__________________________________________________________________________ 
1* -- -- 10 10 10 10 10 
2* -- -- 10 10 10 10 10 
7 .sup. DDAC.sup.1 
0.75 10 10 8 3 0 
8 DDAC 1.5 10 10 7 1 0 
9 DDAC 3.0 10 3 0 0 0 
10 DDAC 5.0 10 0 0 0 0 
__________________________________________________________________________ 
ORGANISM: Dreissena polymorpha (Zebra mussel) (10 organisms/conc. 2-10 mm 
in size) 
*Comparison Examples 
1. DDAC is 50% didecyl dimethyl ammonium chloride, 10% ethanol and 40% 
water, by weight, available from Calgon as H130.