WO2000020338A2

WO2000020338A2 - Methods for controlling macroinvertebrates in aqueous systems

Info

Publication number: WO2000020338A2
Application number: PCT/US1999/023207
Authority: WO
Inventors: Joseph C. Petrille; Wilson K. Whitekettle
Original assignee: Betzdeaborn, Inc.
Priority date: 1998-10-02
Filing date: 1999-10-01
Publication date: 2000-04-13
Also published as: WO2000020338A3; AR020695A1; AU6415599A; CA2246711A1

Abstract

Methods for controlling the fouling potential of macroinvertebrates are provided. An effective controlling amount of a gas and a biocidal agent is added to an aqueous system suffering from the fouling potential of macroinvertebrates.

Description

METHODS FOR CONTROLLING MACROINVERTEBRATES IN AQUEOUS SYSTEMS

FIELD OF THE INVENTION

The present invention relates to methods for controlling fouling by macroinvertebrates, such as mollusks, in aqueous systems.

BACKGROUND OF THE INVENTION

Cooling systems for both industrial plants and utilities are subject to fouling by macroinvertebrates (i.e., mollusks, barnacles, bryozoans, sponges, tunicates, hydroids, annelids) whether the system is using cooling water on a once-through basis or of the recirculating type. Once- through systems operate by drawing cooling water through the process to be cooled on a one-time basis with a short residence time (usually minutes to hours) and discharging the water directly to a receiving body, whereas recirculation cooling systems require the addition of only a fraction of the system volume as makeup water. Additionally, service water systems such as waste, safety and auxiliary cooling which are often part of these cooling systems are also quite vulnerable to macroinvertebrate fouling, primarily because they do not run continuously, and the conduits are of a small diameter.

The extent and type of macroinvertebrate fouling will depend upon many factors such as the source of the cooling water, the season, the water temperature, the growth rate of the macroinvertebrate, and the linear velocity of the cooling water. Further, because of the large quantities of cooling water used, the locality of the plant will dictate the water's source. A fresh water cooling system will be drawing from a river, a lake, or a well, whereas plants situated along coastal areas will most likely utilize brackish or marine water for their cooling purposes.

Both once-through and recirculating types of cooling water are treated prior to entering the system by screening to remove objects which are large enough that they could damage pumps and heat exchange equipment. This screening does not, however, prevent the passage of early, microscopic life stage or larval stages of the macroinvertebrates, which are the precursors to fouling as growth conditions are usually favorable within these systems. These early life stages of the macroinvertebrates will settle out or attach in low flow areas within the cooling system and grow and accumulate to a fouling size, or be trapped in safety or fire protection systems before being closed up.

For example, mollusks are common macroinvertebrates which can cause fouling problems to marine and fresh water cooling systems. Macrofouling by mollusks, like other groups of fouling macro- invertebrates-barnacles, bryozoans, sponges, hydroids, tunicates and annelids-is initiated by the settlement or attachment of larval and/or juvenile stages that are easily entrained into cooling water systems. Fouling caused by the settlement, attachment and/or biogrowth of the macroinvertebrates in the cooling systems and associated service water systems of the industrial plants and utilities which utilize large quantities of water is a major problem causing a variety of deleterious effects to the structure, operation and safety of these systems.

As indicated in the U.S. Nuclear Regulatory Commission 1984 Report entitled "Bivalve Fouling of Nuclear Power Plant Service-Water Systems", the safe operation of a nuclear power plant is a concern because of fouling caused by the Asiatic clam (Corbicula fluminea), the green lipped mussel (Perna perna), the blue mussel (Mytilus edulis) and the American oyster (Crassostrea virginica). This report describes the correlations between the biology of these bivalve mollusks and the design and operation of power plants that allow bivalves to enter and reside within their cooling water systems.

One of the macroinvertebrates controlled by the method of this invention is the mollusk Asiatic clam, Corbicula spp. As indicated in the article entitled "Freshwater Macrofouling and Control with Emphasis on Corbicula" in the December 1983 Proceedings of the Electric Power Research Institute (EPRI), the Asiatic clam has caused significant incidents of macrofouling to fresh water cooling systems of power plants. Another freshwater mollusk, the Zebra mussel (Dreissena polymorph) causes fouling problems to cooling systems in a similar manner as the Asiatic clam. Both Dreissena and Corbicula have free floating planktonic veliger larvae which allow easy penetration into cooling systems. Similar macrofouling problems plague cooling systems using estuarine, brakish, or marine waters, but with different species of macroinvertebrates. Fouling control of macroinvertebrates, such as mollusks, has been attempted using physical/mechanical and chemical techniques (see, e.g., U.S. Pat. No. 4,328,638), but no truly foolproof combination has been developed.

Chlorine, a commonly used biofouling inhibiting agent, has several limitations with respect to treatment to control macroinvertebrates. Chlorine is very toxic to microorganisms and readily kills them at 1 or 2 mg/liter levels; however, mollusks can survive for a considerable period of time in water containing a much higher level of chlorine because of their anatomic and physiological development relative to microorganisms. Microorganisms must accept the environment they find themselves in and live or die depending upon the nature of the environment. On the other hand, higher animals such as mollusks, and other macroinvertebrates when they find themselves in an environment that is inhospitable, can utilize defense systems to exclude the hostile environment. For example, bivalve mollusks can close their shells to exclude the hostile environment. Bivalve mollusks have very sensitive chemosensors in the mantle lining the edge of their shells and, even when their shells are tightly closed, they can continuously sample the environment to determine when it is safe to open up their shells and start siphoning again. A mollusk immersed in chlorine containing water so that its shell is bleached while closed will open up after the chlorine level drops and resume its life. As a result, biocides that are sensed by the bivalve mollusk's chemoreceptor organs as life threatening are not effective simply because the mollusk will close its shell until the threat passes. Mollusks can remain closed for days and still live and resume normal activity. For these reasons prolonged exposure to chlorine is required to achieve efficacy. Other limitations of chlorine treatment include the chlorine demand of the cooling water which reduces the potency of chlorine, and the strict environmental regulations being imposed which act to severely limit the discharge of chlorine residues, and in some cases seek to eliminate the use of chlorine entirely.

In addition to chlorine, U.S. Pat. Nos. 4,462,914 and 5,192,451 disclose the use of a high density cationic polymer to control Asiatic clams, Corbicula and Zebra Mussels, respectively. While the polymer appears to be efficacious toward these two mollusks after a six day exposure period, it suffers from some of the same drawbacks as chlorine.

The above-mentioned concerns over the potential environmental impact of biocides is well described by the following excerpt from the December 1983 Proceedings of the Electric Power Research Institute: "What can kill inside the power plant may also impact the receiving water body; chemical toxicants are not specific. The perfect chemical would be stable enough to be effective inside the plant, but become non-toxic, via chemical reaction or decay, before or as it entered the receiving water body. So far, no chemical meets these specifications: chlorine and bisulfate/sulfide, which have actually been used in an attempt to control macroinvertebrate fouling, have not been effective alone, or have been successful only under limited conditions. Such a chemical may not exist, but scheduling of application of a chemical at the beginning of scheduled outages may offer a less stringent alternative, because of the possibility of extending holdup times." U.S. Pat. No. 4,561 ,983 discloses the use of nitrostyrene compound to control the fouling potential of mollusks. U.S. Pat. No. 4,579,665 discloses the use of a nitrostyrene compound and an alkyl thiocyanate compound to control mollusk fouling potential.

U.S. Pat. No. 4,816,163 discloses a method for controlling the fouling potential of macroinvertebraes, especially mollusks , in an aqueous system which comprises adding to the system an effective controlling amount of a water-soluble alkyl guanidine salt. U.S. Pat. No. 4,857,209 discloses a method for controlling the fouling potential of macroinvertebrates, especially mollusks, in an aqueous system which comprises adding to the system an effective controlling amount of a water-soluble quaternary ammonium salt with detergent properties.

These approaches, while reducing the problem of the mussel sensing the chemical treatment, still cause environmental discharge problems due to the non-specific toxicity of them toward non-target vertebrate fish and commercial invertebrate species.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to methods for controlling the fouling potential of macroinvertebrates in an aqueous system prone to such fouling comprising adding to the system an effective amount to control fouling of a gas dissolved or introduced into freshwater or marine waters, such as nitrogen, helium, argon, carbon dioxide, carbon monoxide, nitrous oxide, sulfur dioxide, chlorine dioxide, ozone, acrolein, ethylene oxide or combinations thereof. Various gases dissolved or introduced into freshwater or marine waters should prevent or aid in preventing biofouling within water distribution systems. It is theorized that gases such as nitrogen, carbon dioxide, carbon monoxide, nitrous oxide, sulfur dioxide, chlorine dioxide, ozone, acrolein, ethylene oxide or combinations thereof could be effective in controlling or reducing biofouling. By "biofouling," it is meant the macrofouling of organisms (e.g., hydrozoaπs, bryozoans, mollusks, crustaceans, ascidians, polychaeta worms, and barnacles).

By the method of the present invention, the gases are fed, at sublethal doses, either in conjunction with known biocidal agents/ dispersants or, if the treatment is with a gas, to be followed by the addition of the biocidal agent. Biocidal agents which could be introduced along with the gases or shortly after the introduction of the gases include, but are not limited to oxidizing agents such as Cl₂, NaOCI, NaOBr, NaBr, CI02, H₂0₂, organic/inorganic peroxide and peroxy compounds, chloramines, halogen donors, l₂, 0₃, potassium permanganate, non- oxidizing biocidal agents such as isothiazolones, glutaraldehyde, methylene bisthiocyanate, bromonitropropanediol, dibromonitriio- propionamide, dodecylguanidine hydrochloride, β-bromo-β-nitrostyrene, secondary/tertiary amines, quaternary ammonium compounds, phosphonium compounds and other compounds commonly used in the treatment of the cooling waters and in pulp and paper process water.

In a preferred embodiment of the present invention, the treatment may also include the addition of dispersants such as alkyl fatty amides, fatty acid alkanolamides, sulfosuccinates, ethoxylated alkyl phenols, noπionic block copolymers of propylene oxide and ethylene oxide (where the copolymer comprises polyalkylene glycol ethers) and ethylenediaminetetraacetic acid, Mexel™ and Endothal™ materials, and DIDAC quats.

In a further embodiment, a dose of carbon dioxide (about 40- 400mg/L) is injected into the water distribution system in order to narcotize the fouling organism or impair its respiratory gas exchange capacity of oxygen. Once these conditions are achieved, it is anticipated that the fouling organisms will be more sensitized to biocidal agents fed in conjunction or following the addition of the gas treatment.

While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The 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 the present invention.

Claims

We claim:

1. A method for controlling the fouling potential of macroinvertebrates in an aqueous system prone to such fouling comprising adding to said system an effective controlling amount of a combination of:

a) a gas selected form the group consisting of nitrogen, helium, argon, carbon dioxide, carbon monoxide, nitrous oxide, sulfur dioxide, chlorine dioxide, ozone, acrolein, and ethylene oxide, and;

b) a biocidal agent.

2. The method as recited in claim 1 wherein said biocidal agent is selected from the group consisting of Cl₂, NaOCI, NaOBr, NaBr, CI0₂, H₂0₂ and peroxide compounds.

3. The method as recited in claim 1 wherein said combination further comprises a dispersant selected from the group consisting of alkyl fatty amides, fatty acid alkanolamides, sulfosuccinates and ethoxylated alkyl phenols.

4. The method as recited in claim 1 wherein said biocidal agent is selected form the group consisting of chloramines, halogen donors, l₂, 0₃, and potassium permanganate.

5. The method as recited in claim 1 wherein said biocidal agent is selected from the group consisting of isothiazolones, glutaraldehyde, methylene bisthiocyanate, bromonitropropanediol, dibromonitrilopropionamide, quaternary ammonium compounds and phosphonium compounds.

6. The method as recited in claim 1 wherein said combination further comprises a dispersant selected from the group consisting of block copolymers of propylene oxide and ethylene oxide and ethylenediamine tetraacetic acid.

7. The method as recited in claim 1 wherein said macroinvertebrate is selected from the group consisting of mollusks, crustaceans, sponges, hydrozoans, sea anemones, bryozoans, annelids, and tunicates.

8. The method as recited in claim 7 wherein said mollusks are selected from the group consisting of clams, mussels, oysters, and snails.

9. The method as recited in claim 8 wherein said clams are Asiatic Clams and said mussels are Zebra Mussels.

10. The method as recited in claim 1 wherein said aqueous system is selected from the group consisting of cooling water systems, ballast water tanks, cooling ponds, intake piping conduits of municipal drinking water facilities, and ship reservoirs.

11. The method as recited in ciaim 10 wherein said cooling water systems are once-through systems or recirculating systems.