Appendix D-1. Control Options1
Thermal Shock
Hot water treatment can kill dreissenid mussels. Long-term exposure to temperatures of 32°C and
above are lethal to adult zebra and quagga mussels. Time to death depends upon acclimation
temperature of the animal as well as rate of temperature increase. Dreissenid mussels will die in
about 1 hour when placed in water of 37°C. At winter acclimation temperatures (5 to 10°C),
temperatures of 33°C and above will kill zebra mussels within 13 hours. For further information, see
Table 1 below.2 Veligers are more susceptible to high temperatures and will experience high
mortality if the ambient water summer temperature rises above 28°C.3
Freezing
Adult dreissenid mussels die when aerially exposed to freezing temperatures. In winter, populations
can be controlled by dewatering and exposing zebra mussels to freezing air temperatures. Zebra
mussels die in 2 days at 0°C and at minus 1. 5°C, in 5 to 7 hours at minus 3°C, and in under 2 hours
at minus 10°C. Duration to mortality is less for single mussels than for clustered mussels.4
Oxygen Starvation
Stripping oxygen from ambient water, primarily in closed environment such as intake pipe, can be
accomplished by use of oxygen scavenging chemical such as sodium-meta-bisulfite and hydrogen
sulfide gas.5 Time to death depends on the level of remaining oxygen, ambient temperature and the
fitness of the mussels treated. Time to 100% mortality of zebra mussels at 25°C is 12 days at oxygen
saturation of 5%.6 At 15°C, the time to 100% mortality increases to 70 day at the same oxygen level.
Oxygen stripping can also be achieved by cycling ambient water through oxygen-stripping pumps.
The developer of the technology, Wilson J. Browning of Amark Corp., Norfolk County, VA, claims
the equipment can cycle 200 million gallons of water and remove oxygen. Addition of CO2 has also
been proposed as a tool to remove oxygen from water in an industrial setting. Information on the
impact of low oxygen levels on survival and settlement of dreissenid veligers is sparse. From studies
on veligers of other species, oxygen levels well above hypoxia levels impact both the development
and settlement of veligers.
(Note: Portions of the material in this section were taken from California’s Zebra Mussel Early Detection and Public
Outreach Program Final Report (Messer, C. and T. Veldhuizen, 2005 and Mackie and Claudi 2010). Additional
information including the data in Tables 2, 3, and 4 was compiled by Bruce Sutherland, consultant to the Pacific States
Marine Fisheries Commission. )
2 McMahon, R. F., T. A. Ussery, and M. Clarke. 1993. Use of emersion as a zebra mussel control method. Technical
Report No. EL-93-1, US Army Corps of Engineers, Waterways Experiment Station, Vicksburg.
3 Mackie, G. L., and R. Claudi. 2010. Monitoring and control of macrofouling mollusks in fresh water systems. CRC
Press, Taylor Francis Group, Boca Raton.
4 Payne, B.S. (1992a). Freeze survival of aerially exposed zebra mussels. Technical Report ZMR-2-09, U.S. Army Corps
of Engineers Waterway Experiment Station, Vicksburg, MS.
5 USACE-ZMIS at http://www. wes. army. mil/el/zebra/zmis/idxlist. htm.
6 Johnson P. D., and R. F. McMahon. 1998. Effects of temperature and chronic hypoxia on survivorship of the zebra
mussel (Dreissena polymorpha) and Asian clam (Corbicula fluminea). Canadian Journal of Fisheries and Aquatic Sciences.
55:1564–1572.
1
Oxygen Starvation - Benthic Mats
Researchers from the Rensselaer Polytechnic Institute in New York are investigating the use of
benthic mats that would cover the sediment and adult mussels, thus depriving them of oxygen.
Preliminary laboratory bioassays carried out in aquaria demonstrated that benthic mat covering of
zebra mussels for 2 weeks resulted in mortality rates of 14. 9–100%, while mortality rates were 2. 2%
or lower for control aquaria without mats. In laboratory studies in which mussels were covered for 4
weeks, mortality rates of 20–100% occurred, and did not vary significantly with duration of covering
or size class. Measurements of several water chemistry parameters beneath mats, including dissolved
oxygen, ammonia, calcium and magnesium and pH, indicated that dissolved oxygen concentration
was the only parameter to exhibit both significant change and a consistent trend over the course of
the study, declining from nearly 100% saturation to a mean of 16. 5% saturation, and remaining at
this level for the duration of the experiment (Sandra Nierzwicki-Bauer, personal communication,
2008).
In field studies carried out in New York’s Saratoga Lake, divers created treatment and control zebra
mussel colonies at 2m depths on a rocky substrate by placing rocks with attached mussels on
fiberglass screens atop gravel beds. During a field trial where two treatment colonies, composed of
about 30,000 mussels each, were covered with 4m2 mats, mortality rates exceeded 99% after nine
weeks of covering. As observed in the laboratory tests, dissolved oxygen concentrations declined
significantly under the mats, correlating strongly with increased mortality (Sandra Nierzwicki-Bauer,
personal communication, 2008).
Desiccation
Desiccation is a viable option for eradicating adult mussels from areas that can be dewatered for
several days. Alternatively, desiccation can also act as a population control method in areas that
cannot be completely dewatered. For example, reservoir levels can be lowered to expose dreissenid
mussels inhabiting shallow water. Depth of colonization is dependent upon water temperature,
oxygen content, and food availability in a particular body of water. Higher population densities tend
to be found above the thermocline, but quagga mussels, in particular, have been found exist at
depths greater than 100m.
Temperature is positively related, and humidity is negatively related, to adult mussel survival. As
humidity increases and temperature decreases, survival increases (Table 1). Aerial exposure of zebra
mussels to temperatures exceeding 25°C, will result in 100% mortality in 2. 1 days. Temperatures
over 32°C are lethal within 5 hours. Instantaneous mortality occurs at 36°C. At temperatures below
30°C, time to mortality is dependent upon relative humidity.
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Table 1. Number of days to 100% mortality of adult zebra mussels aerially exposed to
different levels of relative humidity and air temperature.7
Days to 100 % Mortality at Air Temperature, °C
Relative Humidity, %
5
15
25
95
26. 6
11. 7
5. 2
50
16. 9
7. 5
3. 3
5
10. 8
4. 8
2. 1
Manual Removal
When found in relatively small numbers, manual removal may be an effective way to reduce
dreissenid populations and potentially even eradicate them if reproduction has not yet occurred.
Manual removal can take place via hand extraction or via mechanical scraping and suction, typically
using divers. In Lake George, New York an effort involving hand harvesting by divers appears to
have significantly reduced an introduced population. Divers removed 267 mussels in 1999, followed
by a peak of nearly 20,000 in 2000. Since then, ongoing removal efforts have yielded fewer than
2,000 mussels per year (Sandra Nierzwicki-Bauer, personal communication, 2008). The apparent
eradication of the nonnative sabellid polychaete worm, Terebrasabella heterouncinata, in California,
provides analogous evidence to the role of hand removal as a control technique. After this marine
pest was found at an intertidal site outside of an infected abalone culture facility, over 1. 6 million
native black turban snails (Tegula funebralis)—the preferred native host—were extracted by hand,
along with other infested material. This effort reduced the transmission of the pest species to the
point that it no longer was detectable in follow-up surveys.8
Predation
The relatively soft shells of dreissenid mussels and their exposure (on substrates as opposed to
buried in sediment) make them vulnerable to predation. Possible predators of adult mussels include
some species of carp, catfish, bullhead, sucker, sunfish, sturgeon, crayfish, and muskrats. A possible
predator of veligers is the American shad. However, there is no evidence of predation control in the
Great Lakes, Ohio River, and Poland. There is some evidence of population reduction in the
Hudson River. Despite the lack of clear evidence of population control through predation, it is
recommended that harvest of predatory species in mussel-infested waterbodies be minimized.
Acoustic Deterrents
Several acoustic deterrents have not been proven effective in commercial installations. If developed,
acoustic deterrents could be environmentally friendly and have a low likelihood of harming nonMcMahon, R. F., T. A. Ussery, and M. Clarke. 1993. Use of emersion as a zebra mussel control method. Technical
Report No. EL-93-1, US Army Corps of Engineers, Waterways Experiment Station, Vicksburg.
8 Culver, C. S., and A. M. Kuris. 2000. The first apparent eradication of a locally established introduced marine
pest. Biological Invasions. 2:245–253.
7
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targeted organisms. Cavitation is a form of acoustic energy that initiates the formation and collapse
of microbubbles. At frequencies between 10 and 380 kHz, this type of energy has demonstrated
mortalities of veliger, juvenile, and adult zebra mussels. Exposure times are in the range of seconds
for veligers, minutes for juveniles, and hours for adults.9
Sound treatment using low frequency energy has prevented the settlement of zebra mussels and
could be a valid option for reducing the spread of the organisms. Sound waves between 20Hz–20
kHz have caused veligers to detach and sink. Ultrasound waves between 39–41kHz have fragmented
veligers in a few seconds and killed adults in 19 to 24 hours.10
Vibration is the use of solid-borne acoustic energy in mechanical structures. This treatment will only
work on structures that can be subjected to vibration and not suffer structural deterioration.
Vibrational energy is effective in killing zebra mussel veligers and juveniles at just below 200 Hz and
between 10 and 100 kHz.11
Plasma pulse technology (Sparktec Environmental, Inc.) has shown some effectiveness in
controlling zebra mussels in intake pipes. The system works by releasing stored energy and creating a
spark between two electrodes. This causes an intensive shockwave, a steam bubble, and ultraviolet
light.12 Deployment of the Sparker technology in a pipeline on Lake Champlain prevented settlement
of veligers in an area up to 100 feet from the Sparker.13 Attempts to re-test this technology by
Reclamation have not been successful to-date.
Electrical Deterrents
Electrical current could be used both to disable veligers in a stream of water and to create a static
field on a surface to be protected from settlers. Number of studies exists documenting some success
with both applications. To-date no commercial installation exists using this technology.
Filtration - Media Filters
This technology is capable of removing all stages of all dreissenid mussels and protecting all
downstream systems and components. Sand or media filters are frequently used for protection of
individual components in power plants. For protection of moderately sized intakes, infiltration galleries
have been constructed in some locations.
9
Kowaleski, J. J., and P. H. Patrick. 1993. Acoustics as a possible mitigation strategy against zebra mussel settling. In
Proceedings of the Third International Zebra Mussel Conference, Toronto, Canada, February, 1993.
10 Sonalysts, and Aquatic Sciences. 1991. Zebra mussel deterrence using acoustic energy. Research Report 90-38. Empire
State Electric Energy Research Corporation.
11 Kowaleski, J. J., P. H. Patrick, and A. E. Christie. 1993. Effects of acoustic energy on the zebra mussel (Dreissena
polymorpha). In Zebra Mussels: Biology, impact and control, T. Nalepa and D. W. Schloesser, eds.pp.167–174. Boca
Raton: CRC Press.
12 Mackie, G. L., P. Lowery, and C. Cooper. 2000. Plasma pulse technology to control zebra mussel biofouling. ERDC
TN-ZMR-2-23 US Army Corps of Engineers, Waterways Experiment Station, Vicksburg.
13 Schaefer, R., and R. Claudi. 2004. Development of an efficient low-cost Sparker technology for controlling zebra
mussels. Presentation at the Thirteenth International Conference on Aquatic Invasive Species, Ennis, Ireland, September
20–24, 2004.
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Filtration - Mechanical Self Cleaning Filters
This technology is capable of removing all stages of dreissenids if an appropriate screen size and
configuration is used. Most conventional industrial strainers have strainer screen openings that will
prevent some translocating mussel adults and most shell debris from fouling the raw water systems.
None, however, will protect against the introduction of larval stage organisms. In most instances, it
is not possible to retrofit existing strainers with finer screens and hope for successful mitigation. The
performance of such modified strainer or filter tends to deteriorate, excessive clogging of the screen
may result in stretching and tearing of the material, the backwash system may prove to be inadequate
and the pressure drop caused by the strainer may be unacceptable.
Different types of filters, designed primarily for the removal of small particles, have been tested for
dreissenid veliger control by a number of different organizations. Wedge wire slot filters/strainers
have difficulty in excluding veliger stages of dreissenids. This is likely due to the fact that wedge wire
type screen filters are being designed to remove inorganic matter, such as quartz or metal shavings,
but they are not designed to stop organic matter from passing through the screen. Organic particles,
due to their flexible nature, tend to “sneak through” the wedges of the screen.
Hydrocyclone or centrifugal separators filters were initially thought to be a mitigation option for
facilities that already employ this technology for silt removal. A 1992 study14 tested two different
centrifugal separators and concluded that the removal rate of larval mussel stages was no greater than
50%. A later study15 as part of a ballast water project confirmed demonstrated that a 100µm
hydrocyclone filter was 30% less effective in removing both biotic and abiotic materials than either the
disc or screen-type automatic backwash filter. The lack of success is probably due to the close to
neutral buoyancy of dreissenid veligers. Recently, hydrocyclone filters have been used successfully for
removal of New Zealand mud snails in fish hatchery applications.
Excellent results were obtained by Ontario Power Generation using a continuous backwash, pleated
screen filter16 and by the New York Power Authority using a modified clean-in-place bag filter17 in
eliminating dreissenid veligers from incoming water.
Many filters are very good at removing all or most particles from the water stream, but most filters
are not able to process large volumes of water efficiently. Filters that use stainless steel, square weave
mesh and automatic backwash seem to have the best balance between particle removal efficiency
and volume of water filtered. A number of manufacturers produce such filters, but they must be
carefully evaluated to ensure efficacy. A rugged design with a stainless steel mesh no greater than 80
microns in either direction and an efficient self-cleaning system should be capable of preventing the
majority of ready-to-settle veligers from entering the downstream system.
Acres International. 1992. The study of centrifugal separators for zebra mussel control. Report P9895.29.01.
Parsons, M. G., and R. W. Harkins. 2002. Full scale particle removal performance of three types of mechanical
separation devices for the primary treatment of ballast water. Marine Technology 39:211–222.
16 Koopmans, R., and R. W. Hughes. 1993. Mechanical filtration as a control measure for zebra mussels. In Proceedings
of the Third International Zebra Mussel Conference, Toronto, Canada, February, 1993.
17 Kahabka, J., and A. Talgo. 1993. Filtration as a control method for zebra mussels: A small hydroelectric plant
application. In Proceedings of the Third International Zebra Mussel Conference, Toronto, Canada, February, 1993.
14
15
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40 Mic ron F ilter T es ts
400
Numer of Velig ers
350
300
250
200
B efore
150
A fter
100
50
0
< 100
100-200
200-400
> 400
Velig er S iz e (µm)
80 Mic ron F ilter T es ts
600
Number of Velig ers
500
400
300
B efore
A fter
200
100
0
< 100
100-200
200-400
> 400
Velig er S iz e (µm)
Results from filter evaluation tests carried out on the Lower Colorado River18
Filtration systems are not appropriate for water streams with continuously high sediment load.
Under such conditions, the backwash system may not be able to remove the sediment cake that
builds up on the screen. Very efficient backwash systems are capable of coping with higher sediment
loads.
Claudi, R., T. H. Prescott, and A.C. Taraborelli. 2008. Assessment of the ballast safe filter performance in removing
quagga mussel veligers from the raw water of Lake Havasu. Report for Sigma Design Company LLC, Springfield, N.J.
and Maritime Solutions, Inc.
18
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UV Radiation
The term ultraviolet is applied to that portion of the electromagnetic spectrum between visible light
and x-rays, typically between 190 and 400 nm. This region is commonly subdivided into UVA, UVB
and UVC, where UVA corresponds to the longer wavelength (lower energy regime), through to
UVC, which corresponds to the shorter wavelength, higher energy end of the UV spectrum.
UV radiation is an effective method for preventing downstream settlement of dreissenid veligers.
Based on work by numerous authors in the early 1990s, the UVB and UVC portions of the
spectrum were found to be most effective for dreissenid veliger control. The basis for the control is
thought to be the impact of the UV light on the essential functions of the veliger, thereby
inactivating the organism and preventing attachment. The determination of the most effective
wavelength and the radiation dose to achieve either immediate or latent mortality of the veligers or
juveniles has been the subject of numerous studies.
Medium pressure mercury lamps have been shown as capable of delivering an effective dose to
eliminate downstream veliger settlement.
A full-sized pilot UV system was installed at a power plant on Lake Huron in 1999. Twenty medium
pressure lamps were arranged in four frames each containing five lamps (Figure 1). The total volume
treated was 760 L/s (12,000 US gpm). The system was sized to deliver a radiation dose of 70–100
mWatt-scm2 to all particles passing through. This system was the only means of protection on this
cooling system. During the operation of the UV system, lamps had to be serviced, the system
experienced numerous upsets and occasionally it was even taken out of service inadvertently. Despite
these issues, there was an 85% reduction in settlement in the system, when compared to control.19
Figure 1. UV lamp rack used in an
open channel system for dreissenid
veliger control.
The UV systems currently being tested for control of various species in ballast water are rugged and
dependable. They use UV lights installed inside a pipe, rather than the open array shown above, and
they have been engineered to deliver a maximum dose in the least amount of time.
Pickles, S. B. 2000. Use of ultraviolet radiation for zebra mussel control at Ontario Power Generation. Presentation at
the Tenth International Aquatic Nuisance Species Conference, Toronto, Canada, February, 2000.
19
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The effectiveness of a UV system is dependent on the characteristics of the raw water being treated.
Factors, such as water transmittance, presence and size of suspended solids, iron, hardness and
temperature all affect the efficacy of the UV system. Treatment systems must be designed for the
worst case scenarios. This means designing for peak flows, end of lamp life intensity, minimum
transmittance and maximum suspended solids at the installation location. The aim of the system is
to achieve 100% immediate or latent mortality in all ready to settle veligers which pass through. If an
adequate dose is not delivered at this point, downstream settlement will occur as UV-based systems
have no residual toxicity that could impact areas outside the influence of the lamps.
Three separate studies on the Lower Colorado River have shown the extreme effectiveness of
medium pressure lamps in preventing quagga mussel settlement downstream.20
Chemical Treatment
There are 2 main categories of chemicals used to treat zebra mussel infestations: oxidizing biocides,
and non-oxidizing biocides. The most susceptible life stages to chemical treatment are all stages of
veligers and post spawn adults. Application rates and exposure time required data for these
chemicals have been gathered from laboratory studies, power plant, and water treatment plant
applications.
Oxidizing Biocides

Chlorine, bromine, hydrogen peroxide, ozone, and potassium permanganate are examples of
oxidants that are used to control dreissenid mussels. The chemicals have been used by the
water treatment industry for disinfection since the late 1800s. Because these chemicals have
been in use for so long, their effect on the environment is well understood and
documented.21 In mussels, oxidizing chemicals are thought to work by oxidizing the gill
lamellae as well as other organs, eventually causing death. Dreissenid mussels can recognize
oxidizing chemicals as toxins and close their shells when oxidizing chemicals are present.
Periodically, they reopen their shells to “test” the water. Depending upon water temperature,
respiration rate, and stored nutrient reserves, dreissenid mussels can remain closed for many
days before resuming respiration. Once this occurs, mortality is swift. Therefore, required
exposure time for oxidizing biocides can range from 1–3 weeks. Oxidizing chemical can also
be used to prevent settlement by either continuous, semi-continuous, or period application.
Chlorination in various forms, such as sodium hypochlorite, chlorine gas, chlorine dioxide,
and chloramines, is the most common method of dreissenid mussel control. The use of
chlorine and its various forms is usually limited to non-open water situations because of its
high toxicity to other forms of aquatic life. Treated waters must either be dechlorinated or
held until the residual chlorine has dissipated before discharge.
An example of chlorine use that may be applicable to a small isolated population of
dreissenid mussels is the practice of using tarps to seal off an area and then injecting chlorine
into the enclosed area. The Washington Department of Fish and Wildlife used this method
20
Claudi, R., A. Graves, A. C. Taraborelli, R. J. Prescott, and S.E. Mastitsky. 2012a. Impact of pH on survival and
settlement of dreissenid mussels. 7(1). doi:10.3391/ai.2011.ICAIS.
http://www.rntconsulting.net/Publications/Articles.aspx
21 Claudi, R. and G. L. Mackie. 1994. Practical manual for zebra mussel monitoring and control. Lewis Publ., Boca
Raton, FL. ISBN 0-87371-985-9. 256 pp.
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in October of 2004 to successfully eradicate a small population of nonindigenous tunicates
in Puget Sound near the City of Edmonds (Pers. Comm., Pam Meacham, WDFW, February
2007). This method was also used in Huntington Harbor, California, to eradicate a marine
alga, Caulerpa taxifolia. Patches of Caulerpa were treated by covering them with black PVC
tarp and injecting liquid chlorine under the tarp. The edges of the tarp were sealed to the
bottom with sandbags. All of the organisms under the tarps were killed by the treatment, and
the tarp method avoided impacts to surrounding areas.22

Hydrogen peroxide. Although toxic to dreissenid mussels, hydrogen peroxide is rarely used
because of the high dosage rates and high cost.

Ozone is effective at the same doses as other oxidants. 0. 5 mg/l has been shown to cause
100% mortality of veligers in 5 hours and adults in 7–12 days. Application of 0. 3ppm of
ozone during the mussel breeding season had prevented mussel settlement and eliminated all
adults already in place in a cooling water system of a coal fired power plant. Ozone dissipates
quickly and is considered less harsh on the environment. High capital cost of the equipment
has been a barrier to wider use.

Potassium permanganate is also an effective chemical for mussel control and has been used
by a number of water treatment plants in North America. At higher doses, potassium
permanganate stains water pink. Fear of pink water has been a barrier to the adoption of this
control strategy. In 1992–93, the Central Lake County Joint Action Water Agency fed an
average dosage of 0. 11 mg/l potassium permanganate (maximum dosage of 0. 22 mg/l) into
raw water from May to October to successfully control zebra mussel settlement. The City of
Racine, Wisconsin used an average dose of 0. 2–0. 25 mg/l potassium permanganate to
control zebra mussels in their water intake facilities. Upstream of the application point,
extensive zebra mussel colonization was reported, but the pipes and wet well downstream of
the application point were free of attached zebra mussels.

Sodium permanganate liquid is commonly used in drinking water treatment to control tastes
and odors, remove color, and oxidize dissolved iron and manganese. Sodium permanganate
has only been used effectively for zebra mussel control at the WTP in Findlay, Ohio. The
City of Findlay increased the sodium permanganate dosage from 0. 3 mg/l to 1. 25 mg/l
during the course of a year. This was effective in eliminating zebra mussel colonization
downstream of the application. Water treatment plants in Neenah, Wisconsin, and Keokuk,
Mississippi, have also used sodium permanganate for mussel control, but their effectiveness
is not well documented.
Non-oxidizing biocides
Non-oxidizing biocides are generally not recognized as noxious substance by the dreissenid mussels.
Mussels continue to filter water, exposing themselves to these chemicals. Elimination of adult
mussels with non-oxidizing chemicals can be accomplished in hours compared to days for oxidizing
chemicals.

22
The most commonly used non-oxidizing compounds are proprietary molluscicides (e.g.,
Clam-Trol, Bulab, and Bayluscide). These are very effective for controlling dreissenid
mussels, but they are also toxic to many fish and other aquatic species at the required
concentrations. Most proprietary molluscicides must be detoxified prior to release to the
www. sccat. net/eradication. php
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environment. These compounds are usually deactivated by releasing slurry of bentonite clay
into the water. The cationic or surfactant active ingredients bind onto the clay, becoming
inactive. The clay settles out of the water column and becomes part of the bed sediments.
The compounds are eventually degraded by microbial action. As is the case with most
chemical treatments, the proprietary molluscicides are less effective at lower water
temperatures, so treatment is recommended during warmer months. The chemicals are
usually administered with equipment supplied by the vendors. An example of the successful
use of non-oxidizing chemicals to control the Asian clam in the southeastern United States
can be found in a paper entitled “Strategies for application of non-oxidizing biocides.”23
Additional information on most of these chemicals, such as formula, manufacturer, and
application method, is available at http://www. wes. army. mil/el/zebra/zmis/idxlist. htm.
pH adjustment—under 7 or over 9. 5—There continues to be some uncertainty as to what pH
level can be tolerated by larval stages of dreissenids and at what pH adults will survive for prolonged
periods of time. Successful development of zebra mussel veligers requires a pH range between 7. 4
and 9. 4, with optimal conditions at 8. 5.24
In a series of experiments done on the Lower Colorado River and at San Justo Reservoir in
California, the effects of both low and high pH was tested on both the settlement prevention and
mortality of adult zebra and quagga mussels. Water with continuously adjusted pH below 6. 9
prevented the settlement of quagga mussels, and long term exposure to this pH caused significant
mortality in adults. By comparison, settlement was not completely prevented in the zebra mussel
population, and the mortality of adults was much low.
At pH levels over 9. 6, new settlement by zebra mussels was almost entirely absent. The observed
mortality of adult zebra mussels was low, but did tend to increase with increasing pH.
In addition, short-term experiments testing the response of zebra mussels to both low and high pH
extremes were carried out at San Justo Reservoir. Both extremes in pH caused swift mortality in
adult mussels.
From these studies it seems that pH adjustment could be used both as a preventative treatment to
eliminate settlement by dreissenid mussels and as an end-of-season treatment to eliminate adults.
However, high pH treatment would have to be tailored to site specific water quality to prevent or
minimize formation of precipitate during treatment.
Copper-based algaecides—Various copper based algaecides used both for control of aquatic
weeds and algae have been reported as having an effect on dreissenid mussels when applied for
control of aquatic weeds and algae. Copper products (copper sulfate and copper carbonates or
23
Green, R. F. 1995. Strategies for application of non-oxidizing biocides. Proceedings, Fifth International Zebra Mussel
and Other Aquatic Nuisance Organisms Conference, Toronto, Canada, February 1995. 175–181.
24
Sprung, M. 1987. Ecological requirements of developing Dreissena polymorpha eggs. Archives of Hydrobiology
Supplement. 79:69–86.
D1–9
chelates) can be used to control mollusks in open water systems, but require a Special Local Need
Label (also known as a Section 24-c) issued by the USEPA.
In a study done on the Lower Colorado River and at San Justo Reservoir in California, various
copper-based products were tested for their effect on both quagga and zebra mussels at
concentrations generally used for weed and algae control. At those levels, all of the products resulted
in significant mortality of dreissenid adults within 96 hours.
Quagga mussels appeared more susceptible than zebra mussels to these copper-based products.25
Endothal—Two formulations of endothal-based algaecides exist. The first formulation is the dipotassium salt of endothal sold under the trade name of Cascade®. The second is the amine salt of
endothal under the trade name of Teton for algae control and EVAC for the control of dreissenid
mussels. In experiments carried out in mobile flow through laboratories, no significant mortalities
were detected when either quagga or zebra mussels were exposed to various concentrations of the
di-potassium salt
Exposure to product containing amine salt resulted in significant quagga mussel mortalities. Sixty
percent mortality was reached after 24 hours at 2 ppm and after 12 hours at 3 ppm at 20ºC. Both 2
ppm and 3ppm treatments showed 100% mortality after 96-hour exposure. These experiments were
conducted in the Lower Colorado River.
By comparison, zebra mussels in San Justo Reservoir, the site of the second experiment, exhibited
significant mortality only at 3 ppm, after 60 hours. At 96 hours, mortality reached almost 40% and
seemed to be still increasing when the experiment was terminated.
Mortalities for both species increased with increased ambient temperature.
For locations where algaecide treatment is required and amine salt of endothal is chosen, dreissenids
will also be affected.26
Potassium salts—Potassium compounds are toxic to most bivalves, including dreissenids and
corbiculids. Using flow through experiments in mussel infested waters, it was concluded that 20
mg/L caused 100% mortality in adults in 52 days while preventing any new settlement.27 Total
mortality of small zebra mussels (7–11 mm) at a power plant on the Moselle River was achieved in
48 hours using 600 mg/L of KCl.28 In addition to causing mortality, potassium in various forms has
Claudi, R., T. H. Prescott, S. Mastitsky, and H. Coffey. 2013. Efficacy of copper based algaecides for control of quagga
and zebra mussels. Report prepared for California Department of Water resources, RNT Consulting, Inc., Picton,
Ontario.
26 Claudi, R., A. C. Taraborelli, and T. H. Prescott. 2013b. Experimental protocol for Endothal efficacy for control of
quagga and zebra mussels. Prepared for Bureau of Reclamation, Task Order Number: R11PD81448. IDIQ Contract:
R10PC80264.
27 Lewis, D. P., J. Piontkowski, E. Neuhauser, and J. Knowlton. 1996. Chronic exposure of adult and larval mussels at
low level potassium concentrations: Laboratory studies. In Proceedings of the Sixth International Zebra Mussel and
other Aquatic Nuisance Species Conference, Dearborn, USA, March, 1996.
28 Khalanski, M. 1993. Testing of five methods for the control of zebra mussels in cooling circuits of power plants
located on the Mosselle River. In Proceedings of the Third International Zebra Mussel Conference, Toronto, Canada,
February, 1993.
25
D1–10
been observed to prevent valve closure in mussels and reduced filtration rates.29 Potassium chloride
is used primarily as an end-of-season treatment for a number of closed loop systems, such as fire
protection systems. Potassium chloride seems to be particularly effective in these types of semi-static
systems due to mode of action and the fact that it does not possess the inherent demand
characteristics typical of oxidants. Concentrations between 88–288 mg/l are necessary to cause swift
mortality in adults. Such concentrations will likely kill native mussels as well, but are non-toxic to
fish. In 2006, KCl was used to successfully eradicate zebra mussels from a rock quarry pond in
Virginia. A 100% kill was attained with minimal environmental impacts to other aquatic species and
to the drainage waters downstream. This method seems promising if a lethal concentration of KCl
can be maintained for a 2–3 week period. More information about this project can be found at:
http://www. dgif. virginia. gov/zebramussels/index. asp.
Although potassium compounds are non-toxic to higher organisms, such as fish, the toxicity to
native bivalves makes the approval for use of potassium salts in once-through systems unlikely.
Biobullets—The product known as “BioBullets” takes advantage of the potassium salt toxicity
while overcoming the dreissenid mussel reaction to noxious substances by encapsulating a core of
potassium chloride (KCl) with an edible non-toxic coating. These approx. 40 micron particles are
readily ingested by dreissenid mussels, leading to a much faster death than the application of
potassium chloride alone. BioBullets are not only toxic to dreissenids. Other filter feeders may also
ingest the BioBullet particles leading to negative impacts on other species, as is the case with
majority of other chemical control strategies.30
Copper ion generator—Dissolution of copper and aluminum anodes by electrolysis has been used to
protect ship cooling systems from macrofouling for at least 40 years. Based on the marine experience, a
series of experiments was conducted to determine if the same technology could be used against
dreissenid mussels.31 They concluded that a continuous dose of 10 ppb of copper ion would limit veliger
settlement in system protected. This technology was commercialized under the trademark of
MacroTech® Copper Ion generator. Wisconsin Energy Corporation We Energies uses this copper ion
technology to control dreissenid mussel infestation in its Oak Creek Power Plant service water system.32
Although the copper ion generator does not eliminate all macrofouling in the service water system, the
level of infestation is acceptable to the plant personnel.
As the toxicity of copper in freshwater systems is greatly influenced by water quality, one would
anticipate that different bodies of water would require different levels of copper ion generation to
control dreissenids. The discharge of copper ions into the aquatic ecosystem may not be permitted in all
jurisdictions. This technology is currently being tested by the Bureau of Reclamation, and results are
expected early in 2014.
Wildridge, P. J., R. G. Werner, F. G. Doherty, and E. F. Neuhauser. 1998. Acute effects of potassium on filtering rates
of adult zebra mussels Dreissena polymorpha. Journal of Great Lakes Research. 21:629–636.
30 Aldridge, A. D. C., P. Elliot, and G. D. Moggridge. 2006. Microencapsulated Biobullets for the control of biofouling
zebra mussels. Environmental Science and Technology. 40:975–979.
31 Blume, J. W., P. C. Fraleigh, and W. R.v anCott. 1994. Evaluation of copper ion and aluminum floc for preventing
settlement of zebra mussels. In Proceedings of the Fourth International Zebra Mussel Conference, Madison, USA,
March 1994.
32 Babinec, J. 2003. Copper ion treatment for zebra mussel mitigation in house service water systems. Power Plant
Chemistry. 5:539–547.
29
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Bacterial Toxin (Zequanox) —The naturally occurring bacterium Pseudomonas fluorescens strain
CL145A is the active ingredient in a microbial molluscicide product registered under the brand name
Zequanox (ABN MBI-401 SDP). Zequanox was registered in the United States and Canada in 2012
and is currently registered in most states where zebra mussels occur or may spread in the future. It is
registered only for the control of zebra and quagga mussels and has not been shown to have any
significant activity against Asiatic clam, other invasive mollusks, or native North American bivalves.
The bacterium was discovered and developed by New York State Museum (NYSM) and licensed to
Marrone Bio Innovations for commercialization. Pseudomonas fluorescens is ubiquitous in the
environment, and lab studies have indicated that when zebra or quagga mussels ingest artificially
high densities of strain CL145A, a toxin within these bacterial cells destroys their digestive system.
Dead bacterial cells are equally as lethal as live cells, providing evidence that the mussels die from a
toxin, not from infection. The current formulation of Zequanox is composed of 50% killed cells of
Pseudomonas fluorescens strain CL145A and 50% food-grade tolerance-exempt inert ingredients
(carriers in the spray drying process). Future formulations of the product may be freeze-dried or
liquid.
Laboratory trials to date have been very encouraging regarding non-target safety (Malloy 2008). At
dosages that produced high zebra mussel mortality (76–100%), no bacteria-induced mortality has
been recorded among any of the non-targets, including fish, ciliates, daphnids, and bivalves (Malloy
2008). Mortality in sensitive aquatic species, such as daphnia and rainbow trout, have only been
induced at high concentrations (100–200mg/L) during very long exposure periods (96hr–30 days).
Because predicted environmental concentrations (PECs) are very low and the product’s activity has
a half-life of 12 hours, impacts to fish, native mollusks, algae, plants, and other aquatic organisms is
highly unlikely. Although originally developed as an environmentally safe alternative for chlorination
in power plants, the non-target safety of this bacterial control agent may allow this technology to
also be used for zebra and quagga mussel control in open waters, such as lakes and rivers. Zequanox
was registered for use in industrial sites in 2012, and an expansion of allowed uses, to include open
waters, is currently pending approval at the Environmental Protection Agency in early-mid 2014.
Further information on this control method can be found at www.marronebioinnovations.com.
No-Growth Materials (anti-fouling paints)—Can be effective in preventing zebra mussel
attachment, however, the leachate can be toxic to other organisms. Anti-fouling paints are
expensive to use and only feasible in certain situations.
The following three tables provide a more detailed look at these control methods including target
populations, application rates, efficiency and toxicity. Table 2 details non-chemical methods. Table 3
describes chemical control methods, and Table 4 identifies some of the most common commercial
products.
Anti-fouling coatings—Historically, the majority of developmental work in antifouling
paints/coatings has been directed towards prevention of barnacle growth on ships. In fresh water,
antifouling coatings’ primary use has been for the prevention of dreissenid mussel attachment to
structures exposed to raw lake water.
D1–12
The following substrate preference by dreissenids was established33 by using settling plates; copper <
galvanized iron < aluminum < acrylic < PVS < teflon < vinyl < pressure treated wood < black steel
< pine < polypropylene < asbestos < stainless steel. For pipes the preference was as follows; copper
< brass < galvanized iron < aluminum < acrylic < black steel < polyethylene < PVC < ABS.
Anti-fouling coatings containing the biocide TBTO (tri-butyl tin oxide, an organotin oxide), have
been used successfully for prevention of mussel attachment and growth in Europe. They are banned
in Canada and in most of the states in the U. S. Copper has also been used successfully in antifouling
coatings, but leaching of copper ions from such coatings may result in unacceptable copper
concentrations in the discharge water. Johnson Screens Company has developed a copper alloy
under the commercial name “Z-Alloy” for water intakes structure which has been reported as both
successful and as having failed. Tests done by the US Bureau of Reclamation in 2008 on wedge wire
screens made of Copper-Nickel (90-10) have shown quagga mussels settling heavily on this material
within four month.34
The overall trend is toward the use of environmentally benign foul release coatings which form a
physical barrier to attachment. The most promising coatings at this time are nontoxic, silicone based paints that prevent, or greatly decrease the strength of attachment. The silicone -based
coatings usually require several different layers to be applied to a perfectly clean, white metal surface
or very clean and almost dry (10% or less moisture level) concrete. This tends to make them very
costly ($40 -$100/m2). In addition, the foul release coatings tend to perform better in areas of high
or moderate flow, rather than in quiescent areas.
US Bureau of Reclamation is currently conducting coating trials on the lower Colorado River.35
The following three tables provide a more detailed look at these control methods including target
populations, application rates, efficiency and toxicity. Table 2 details non-chemical methods. Table 3
describes chemical control methods and Table 4 identifies some of the most common commercial
products.
Kilgour, B. W., and G. L. Mackie. 1993. Colonization of different construction materials by zebra mussel, Dreissena
polymorpha. In Zebra Mussels: Biology, impact and control, T. Nalepa and D. W. Schloesser, eds. pp.167–174. Boca
Raton: RC Press.
34 US Bureau of Reclamation. 2009. Preliminary evaluation of quagga mussel fouling potential for Cu-NI (90-10) wedge
wire screen. Research Note: Zebra and quagga mussel research program.
http://www.usbr.gov/mussels/research/docs/researchnotes/ZQMRP-2009-RN-01-CU-NI.pdf
35 http://www. usbr. gov/lc/region/programs/quagga/researchnotes/04CoatingsStudy. pdf
33
D1–13
TABLE 2: Non-chemical treatment methods for dreissenid control.
METHOD
Primary TARGET
AGE
Thermal shock
All
100%
Freezing
Juveniles
Adults
100%
Oxygen starvation –
stripping water of oxygen
Oxygen Starvation Benthic mats
Desiccation
All
Juveniles
Adults
Juveniles
Adults
Manual removal
Juveniles
Adults
All
Veligers
Variable
Acoustic Deterrents
Low frequency sound
Acoustic Deterrents
Ultra sound
Acoustic Deterrents
Vibration
Acoustic Deterrents
Plasma pulse technology
Electrical Deterrents
Low voltage electricity
Filtration
Media filters
Filtration
Self-cleaning mechanical
filters
UV radiation
Veligers
Veligers, translocators
Not commercially
available
Not commercially
available
Not commercially
available
Prevents settling – Not
commercially available
Not commercially
available
100%
Veligers, translocators
100%
Veligers
Bacterial toxin
(Pseudomonas fluorescens)
All
100% prevention of
settlement
95%
Predation
Acoustic Deterrents
Cavitation
All
Veligers
Juveniles
Veligers
Veligers
Potential
EFFICACY
CONTACT TIME
/CONCENTRATION
COMMENTS
13 hours @ 33 °C (winter)
1 hour @ 37 °C (summer)
2 days @ 0 °C
5-7 hours @ –1. 5 °C
under 2 hours @ –10 °C
2 weeks + @ 0 mg/l
Lethal to most aquatic species
Up to 99%
9 weeks
Initial tests promising for limited infestations
100%
Immediate @ 36 °C
5 hours @ 32 °C
2. 1 days @ 25 °C
N/A
Must dewater system for several days
Low
Not commercially
available
Continuous
veligers in seconds @ 10–380 kHz
juveniles in minutes
adults in a few hours
4 to 12 min @ 20 Hz–20 kHz
Inhibits settling
veligers in seconds @ 39–41 kHz
adults in 19-24 hours
intermittent @ 200 Hz & 10–100
kHz
intermittent high energy pulses
immediate results @ 8 volt AC
Prevents settling
Removal of all particles greater than
80 microns
Removal of all particles greater than
80 microns
6 hours
Must dewater system
Must isolate population
Ongoing efforts in Lake George, New York and Lake
Powell
Harvest of potential predatory species should be limited
May affect other species, reduced success in high flows,
needs power source
Not lethal, needs power source
May impact other species, needs power source
Structural integrity may be threatened
Not lethal, private technology
Not lethal, needs power source
Removes all plankton, high total suspended solids
may be a problem
Removes all plankton, high total suspended solids
may be a problem
Lethal to many species, effectiveness may be limited by
turbidity and suspended solids
Low toxicity to other organisms, few treatments needed,
not yet available in commercial quantities.
Extensive information on treatment methods, including information sources, application methods, hazards, etc. is available on the US Army Corps of Engineers website. Information on the
bacterial toxin, Pseudomonas fluorescens is available on the National Energy Technology Laboratory website.
D1–14
TABLE 3: Chemical treatment methods for dreissenid control.
NON- OXIDIZING CHEMICALS
TARGET
AGE
EFFICIENCY
CONTACT TIME/
CONCENTRATION
Veligers
100%
Adults
100%
69. 9%
52. 4%
Potassium salts (KCL)
All
Potassium ion (KH2PO4)
Potassium ion (KOH)
Copper ions
All
All
Veligers
Prevent settlement
50%
95-100%
100%
100%
100%
Copper-based algaecides
All
EarthTec®
CaptainTM
adults
adults
100
85%
0. 5mg/l copper equivalent in 96 hours
1. 0mg/l copper equivalent in 96 hours
NatrixTM
adults
85-100%
1. 0mg/l copper equivalent in 96 hours
Copper Sulfate
adults
50-99%
0. 5mg/l copper equivalent in 96 hours
Adults – Quagga
100%
36 hours of exposure at 1 ppm
24 hours of exposure at 2 ppm
12 hours of exposure at 3 ppm at
ambient temperature of 25º C
At 20º C ambient water temperature 96
hours of exposure at 1 ppm
84 hours at 2 ppm
24 hours of exposure to 3 ppm.
pH adjustment
COMMENTS
under 7 or over 9. 5, pH close to limit
prevents settlement
pH 3 in 96 hours
pH 2 in 96 hours
ph4 in 96 hours
High pH may cause unacceptable
precipitation in water with high scaling
index
50 mg/l
48 hours @ 150 mg/l
3 weeks @ 95–115 mg/l
continuous @ 160–640 mg/l
Less than 10 mg/l
24 hours @ 5 mg/l
10 15µg/L continuous prevents
settlement
Lethal to other mussel species, non-toxic
to fish at required dose rate
As above
As above
Lethal to other aquatic species
Lethal to other aquatic species, efficacy
increases with increasing ambient
temperature
Equally effective on zebra and Quagga
Difference in efficacy between quagga
and zebra mussels
Difference in efficacy between quagga
and zebra mussels
Difference in efficacy between quagga
and zebra mussels
Endothal based algaecides
Teton - amine salt of endothal
Adult zebra
Cascade – di-potassium salt of endothal
none
2%
100%
100%
75%
0
Efficacy differs between quagga and
zebra mussels. Efficacy increases with
ambient water temperature
96 hours at 3ppm at 25º C
Extensive information on the chemical treatment methods listed above, including information sources, application rates, toxic effects, hazards, etc. is available on the US Army Corps of
Engineers website at www. el. erdc. usace. army. mil/zebra/zmis/idxlist. htm.
D1–15
TABLE 4: Chemical treatment methods (commercial products) for dreissenid control.
PROPRIETARY
MOLLUSCICIDES
QUATERNARY
AMMONIUM
COMPOUNDS
Clam-Trol CT 1
TARGET AGE
All
EFFICIENCY
100% 48 hours after
exposure
CONTACT TIME/
CONCENTRATION
1. 95 mg/l @ 11 °C for 12 hours
1. 95 mg/l @ 14 °C for 14 hours
COMMENTS
More toxic to veligers than adults and more
toxic to mussels than to trout. Must be
deactivated with bentonite clay
1. 95 mg/l @ 20 °C for 6–14 hours
Calgon H-130
All
100% after 48 hours
0. 85–1. 12 mg/l
1. 1 mg/l toxic to salmonids, must be
deactivated, corrosive, flammable
Macro-Trol 9210
All
100%
5–50 mg/l continuous
Lethal to aquatic organisms, must be deactivated
with bentonite clay
Bulab 6002
All
100%
2 mg/l 7–10 days
Lethal to fish, especially salmonids. Must be
deactivated with bentonite clay
4 mg/l 5–8 days
PROPRIETARY
MOLLUSCICIDES
AROMATIC
HYDROCARBONS
TARGET AGE
Mexel 432
Deters veliger settlement
EVAC – endothal
formulation
All
Bulab 6009
All
EFFICIENCY
CONTACT TIME/
CONCENTRATION
Dose at 1–4 mg/l once a day
96 hours LC 50 for rainbow trout 11mg/l,
corrosive
100%
0. 3–3 mg/l for 5 to 144 hours
Lethal to fish but rapidly degrades, does not
bioaccumulate
100%
2 mg/l 4 to 10 days
96 hours LC 50 for rainbow trout 1,1 mg/l,
corrosive
4 mg/l 3 to 8 days
OXIDIZING
CHEMICALS
Chlorine
TARGET AGE
Veligers
COMMENTS
EFFICIENCY
100%
CONTACT TIME/
CONCENTRATION
0. 3mg/l TRC (total residual
chlorine) settlement prevention
1mg/l TRC 7 to 14 days
D1–16
COMMENTS
Lethal to many aquatic species , can be
detoxified on discharge with sodium
metabisulphite
PROPRIETARY
MOLLUSCICIDES
QUATERNARY
AMMONIUM
COMPOUNDS
Chlorine dioxide ClO2
TARGET AGE
EFFICIENCY
Adults
100%
depending on ambient water
temperature
All
100%
0. 3mg/l TRC (total residual
chlorine) settlement prevention
All
100%
Veligers
0. 3mg/l TRC (total residual
chlorine) settlement prevention
1mg/l TRC 7 to 14 days
depending on ambient water
temperature
Adults
Hydrogen peroxide
100%
6 hours
High dosage rates required. Lethal to other
aquatic species. Short half-life in water
100%
Veligers in 0. 3ppm continuous
prevents settlement
Lethal to other aquatic species, very short
half-life in water, generally no need to
detoxify on discharge
Juveniles
Ozone
All
COMMENTS
1mg/l TRC 7 to 14 days
depending on ambient water
temperature
Adults
Chloramine
CONTACT TIME/
CONCENTRATION
5 hours @ 0.5 mg/l total
mortality
Adults in 7 days @ 0.5 mg/l
depending on ambient
temperature
Potassium permanganate
All
100 %
2. 0 mg/l for 48 hours
Sodium permanganate
All
100%
0. 3 mg/l to 1. 25 mg/l
D1–17
lethal to other species, at high doses may
turn water pink
The commercial products listed above have been approved for aquatic use by EPA if applied according to label instructions by a licensed applicator. It is important to
note that they may not have been approved by the individual states and must have that approval before they can be applied. The molluscicides have been primarily
developed for use at water impoundment and hydropower facilities, treatment facilities, water intake structures, etc. Their use in open water is not generally
recommended but might be possible under certain circumstances. For example, the herbicide Endothal, has been shown to be effective against zebra mussels and has
been permitted for use in open waters in Washington State to control noxious weeds.
Extensive information on the products listed above, including manufacturer, chemical formulation, application rates, toxicity, hazards, etc. is available on the US Army
Corps of Engineers website.
D1–18