1. What A Homeowner Needs to Know
The Zebra Mussel
What A
Homeowner
Needs to Know
The Zebra Mussel:
What a Homeowner Needs to Know 1

2. June Lake St. Clair
Since its discovery in the Great Lakes in 2

3. Zebra Mussel U.S. Range December 1989 3
...the zebra mussel has spread dramatically throughout inter­connected lakes and rivers...
December 1989 3

4. Zebra Mussel U.S. Range December 1990 4
...in twenty states and three Canadian provinces...
December 1990 4

5. Zebra Mussel U.S. Range December 1992 5
...including: the Great Lakes; the Erie Canal; the Allegheny, Arkansas, Hudson, Illinois, Mississippi, Mohawk, Monongahela, Ohio, St. Lawrence, and Tennessee Rivers; New York's Finger Lakes; Lake Champlain; and the Trent‑Severn Waterway in the Province of Ontario.
December 1992 5

6. Zebra Mussel U.S. Range December 1999 6
Also infested are more than 85 inland lakes in Connecticut, Illinois, Indiana, Michigan, New York, Ohio, Wisconsin, and Vermont. Most of these lakes are not connected to other infested waterbodies.
December 1999 6

7. Potential Zebra Mussel U.S. Range
By sometime in the 21st Century, the zebra mussel may inhabit suitable waterbodies in parts of the lower forty-eight and the southern Canadian provinces.
December 2020? 7

8. The most likely inland spread vector
Recreational Boating...
Biologists believe that transport of the mussels from infested waters to uninfested inland lakes and rivers will continue as a result of natural and human activities. Of particular concern is accidental transport in and on boats trailered from waterbody to waterbody.
The most likely inland spread vector 8

9. Water Treatment Plant Ozone Contact Chamber
(Monroe, MI, WTP)
The highly publicized impacts of zebra mussels fouling major raw water intakes such as those at municipal drinking water treatment plants... 9

10. Circulating Water Pump Bell Housing (Detroit Edison, Monroe, MI) 10
...and electric generation and industrial facilities are well known by anyone who reads newspapers or watches TV news. 10

11. Huge pipes aren’t the only ones at risk.
But…
Huge pipes aren’t the only ones at risk.
Zebra mussels are already clogging thousands of small intakes, as well.
The media has not talked much about zebra mussel fouling of the small water intake pipes of private homes and cottages along North America’s infested inland lakes, streams, and rivers. However, zebra mussels have already impacted hundreds, perhaps thousands of residential water systems. In fact, several seasonal residences in New York’s Finger Lakes have had the mussels make it past their intake pipes and into the cold water pipes inside the cottages! It is estimated that more than one hundred thousand private homes, cottages, and camps in the eastern half of North America have water systems that could become threatened by zebra mussels. 11

12. Why Haven’t We Heard of This Problem Before Now?
Early colonization is spotty with low mussel densities
Densities of mussel veligers in water column are low
Power plants and drinking water facilities have huge water demands and draw in millions of veligers
Power plants and water treatment plants pump water for long periods of time, sucking in more veligers
Many residential systems may face imminent failure but haven’t been clogged yet
Many people affected by power plant or water treat-ment plant shutdowns; clogged residential pipes impact fewer
Why haven’t we heard residential zebra mussel horror stories? Why have power plants gotten all of the press?
First, when a waterbody has just become infested with zebra mussels, colonization tends to be spotty. It’s probable that mussel densities near or within residential intakes are too low to be noticed. 
During the early stages of the invasion, mussel veliger densities in the water column are usually quite low.
Power plants and public drinking water facilities, with their huge water demands, will draw in many more veligers than will residential systems, resulting in those large pipes clogging sooner than residential pipes.
Power plants and drinking water treatment plants also tend to pump water all day, or nearly so, while residential pumping is sporadic and limited. This again results in fewer veligers being pulled into residential intakes and a slower rate of residential pipe clogging.
There may be many residential systems in which failure is imminent but which haven’t gotten bad enough to become public knowledge.
The bottom line, though, is that when a power plant or drinking water plant is shut down, it impacts many people; when a residential pipe clogs, well... 12

13. Watch carefully… Zebra Mussels come in ALL sizes and coloration
patterns
Why do zebra mussels pose such a threat to residential intake pipes? Zebra mussels can be drawn into water intakes as a) microscopic larvae, called veligers, as b) juveniles that crawl in, and c) as adults that break loose from colonies in the waterbody around the mouth of the intakes and are carried in by water currents. 13

14. Water Intakes = Excellent Zebra Mussel Habitat
Continuous source of food and oxygen
Continuous removal of wastes
Protection from predation
Protection from severe weather
Once inside the intake pipes, zebra mussels find an excellent habitat. The flow of water into the pipes brings with it a source of food and oxygen for the mussels…
and carries away the mussels’ wastes…
while the pipes themselves protect the mussels from predation, storm waves, and ice scour. 14

15. The zebra mussel's secret weapon
Byssal Threads…..
Upon entering a water intake pipe, zebra mussels attach by means of tough elastic fibers, called byssal threads. These threads are tipped with a natural adhesive akin to that produced by barnacles.
The zebra mussel's secret weapon 15

16. Once attached, zebra mussels reproduce in copious numbers, forming dense colonies with tens to hundreds of thousands of mussels per square yard. 16

17. Zebra mussels can completely plug small water intake pipes
in very little time
These colonies can completely clog intake pipes and internal plumbing systems. 17

18. Residential Water Systems
Zebra Mussels in
Residential Water Systems
We will take a look at the components of residential water systems and discuss a number of methods for coping with zebra mussels. Not all methods are suited for all situations. Most will need to be fine‑tuned for use in any specific water system. We recommend that homeowners employ the services of a qualified plumbing contractor to develop and install the best alternative for their residential water system. Local, state, or provincial permit authorities should be consulted to determine what, if any, permits might be required for such projects. 18

19. Zebra Mussel Fouling of Residential Water Systems
Intake pipe
Strainer
Foot valve
Pump
Pipe itself
Storage/pressure tank
Distribution pipes
Once inside a water intake pipe, zebra mussels can colonize any part of the system, from the mouth of the pipe in the lake or river…
any strainer at the end of the pipe…
the footvalve…
at the pump…
the pipe itself…
any onshore pressure tank…
and cold water distribution pipes, all the way to the last cold water tap or toilet in the residence. 19

20. Zebra Mussel Impacts on Residential Water Systems
Loss of pumping efficiency
Obstruction of foot valve
Clogging of intake pipe
Wear & tear on pump
Clogging of distribution pipes
Taste & odor problems
Increased corrosion
This can result in a loss of pumping efficiency…
obstruction of intake foot valves…
clogging of intake pipes…
wear and tear on pumps…
clogging of distribution pipes…
production of tastes and smells from the decay of mussels in the pipe…
and increased corrosion of metal pipes. 20

21. Are mussels growing around or within mouth of pipe?
Is there a noticeable decrease in water volume and pressure?
Are there unpleasant tastes and odors in the water?
Homeowners are well advised to periodically inspect the mouth of their intake pipe to determine whether zebra mussels are growing around or within the pipe.
Otherwise, the first indication that zebra mussels are in their water intake could be a noticeable decrease in water volume and pressure…
or unpleasant tastes and odors in the water. 21

22. Factors Influencing Rate of Zebra Mussel Fouling of Residential Water Systems
Water chemistry of the waterbody
Extent of zebra mussel colonization near mouth of intake
Position of the mouth of intake in the water
Composition of the intake pipe
Volume and velocity of water flowing through the pipe
The rate at which a residential water pipe will become clogged by zebra mussels depends upon…
the water chemistry of the waterbody, such as calcium content, pH, and dissolved oxygen…
the extent of zebra mussel colonization on hard surfaces near the mouth of the intake…
the position of the mouth of the pipe in the water…
the material the pipe is made of…
and the volume and velocity of water flowing through the pipe. 22

23. Reducing the Risk of Zebra Mussel Fouling
While it is impossible to ensure with absolute certainty that no zebra mussels will ever get into a residential water system, homeowners can reduce the risk of having their water systems shut down by the pesky mollusk. 23

24. When to Implement Zebra Mussel Control in Residential Water Systems
Continually (no mussels tolerated ever)
Periodically (some mussel growth is allowed, followed by removal of the mussels)
Depending upon the design of a water system and the level of mussel infestation in the waterbody…
control measures can be implemented continually, in essence no mussel build-up is ever tolerated…
or periodically, allowing some mussel growth until an intolerable level is reached, then the mussels are removed from the system. 24

25. Residential Water Systems
Residential water systems using shore-based jet pumps are made up of two general components. First is the offshore component, that is, from the lake or river end of the pipe to the pump on the shore. Residential water systems using submersible pumps in the waterbody pose a special situation, which will be addressed later in this presentation. 25

26. Residential Water Systems
Second is the onshore component, that part of the system from the pump to the coldwater distribution pipes and faucets inside the residence, including the pump itself and any storage tank. 26

27. Residential Water Systems
Most difficult to protect
Often least costly to repair
In most situations, the offshore component will be the most difficult and expensive section to protect against clogging by zebra mussels…
but may be the least difficult part of a residential system to clean out or replace if it does become clogged. 27

28. Residential Water Systems
Easiest to protect
Most costly to repair
The onshore component, on the other hand, will, in most cases, be the simplest and least expensive section to protect…
but the most difficult and costly to clean out if it should become infested. Physically cleaning or replacing clogged coldwater pipes within the walls of a house could be a homeowner’s nightmare. 28

29. Residential Water Systems
Protecting the
Onshore Component of
Residential Water Systems
Once mussels have invaded a waterbody, homeowners should consider taking early action to keep the mussels out of the onshore component of their water system before the system becomes infested. 29

30. Onshore Component Control Alternatives
Replaceable or cleanable in-line filter
Chlorine injection at pump or pressure tank
Combination of filtration & chlorination
Alternatives for keeping the onshore component zebra mussel free include…
the installation of a replaceable or cleanable in‑line filter…
injection of chlorine at the pump or pressure tank…
or a combination of filtration and chlorination. 30

31. In-Line Filtration 40 micron maximum Removes all life stages 31
Assuming the use of a jet pump, on-shore, in-line filtration involves the installation of a whole-house filter on the water pipe. This filter is usually installed after the pump, but before the pipe enters the pressure tank and plumbing system. The filter should be installed on the discharge side of the pump because some older jet pumps pump better against a filter, but may lose their prime if they try to pump through a filter on the intake side of the pump. The filter must be capable of filtering the maximum amount of water expected to be used by the residence in a day. For purposes of this presentation, we will assume an average of 250 to 400 gallons per day for a family of four in a full‑time residence, or as little as 25 gallons per day for a seasonal weekend cottage.
The filter must be able to remove all particles larger than 40 microns, equivalent to about two one-thousandths of an inch…
about 20 microns smaller than the average size of an early zebra mussel veliger, thus providing an additional margin of safety.
40 micron maximum
Removes all life stages 31

32. Whole House In-Line Filters
Single media filamentous “angel hair” ( )
Ceramic filters (50 )
Spun cellulose or ceramic fiber cartridges (<10 )
Dual media filters
Fiber media around activated charcoal core (<10 )
Removes many flavors & odors
Back-flushable filters or microstrainers (<10 )
Whole-house, in-line filters come in a variety of types, including:
single media filters containing filamentous media, like angel hair, capable of removing particles down to 25 to 50 microns…
ceramic filters capable of filtering down to 50 microns…
spun cellulose or ceramic fiber cartridges capable of filtering down to 10 or fewer microns, about five ten-thousandths of an inch or less…
dual media filters with a fiber media surrounding a core of activated charcoal, which is capable of filtering down to 10 microns or smaller and removing many flavors and odors…
and back-flushable filters or micro-strainers that are capable of filtering down to particle sizes less than 10 microns. 32

33. Whole House In-Line Filters
Least expensive
Require periodic filter cartridge replacement
Increased backpressure can force live larvae through filter
Back-flushable filters clean filter media by reversing flow of water and flushing out filter media
The least expensive in-line filters require that…
the owner replace the filter cartridge periodically.
Failure to do so can result in increased backpressure, which can force some live zebra mussel larvae through the filter.
More expensive back-flushable filters clean the filter media by reversing the flow of water and flushing the trapped particles from the filter, similar to swimming pool filters. 33

34. Whole House In-Line Filters
Cleaning / replacement timing depends upon:
Amount of silt, algae, zebra mussel veligers, and other particles drawn into system
Intake’s location in the waterbody
Time of year
The timing between cleaning or replacement of in‑line filters depends upon the amount of…
silt, algae, zebra mussel veligers, and other particles drawn into the system…
the intake’s location in the waterbody, such as proximity to a stream or bluff that would contribute heavy silt loads…
and the time of year. Silt loads may be higher in spring than summer and higher during stormy periods than during periods of relative calm. Algal growth is usually highest in summer and early autumn.
Spring & summer silt loads
Storm silt loads
Summer algal growth 34

35. Whole House In-Line Filters
Do not allow material trapped within filter to bypass the filter during cleaning / replacement
Cleaning / replacement of clogged filters is an on-going cost & time commitment
Automatic back-flushable filters can eliminate one of the maintenance tasks
Caution should be taken that none of the material trapped within a filter is inadvertently allowed to by‑pass the filter during cleaning or replacement.
The cleaning or replacement of clogged filters will be an on‑going cost and time commitment.
Backflushable filters can, for an additional cost, be installed to automatically backflush, eliminating one of the filter maintenance items a homeowner needs to remember. 35

36. In-Line Chlorination Kills all life stages Kills many other pathogens
Another method of protecting the onshore portion of a residential water system is the installation of an in‑line chlorine injector between the pump and the in‑house plumbing. Such chlorinators add about two tenths of a part per million of potable chlorine to the incoming water every time the pump runs. This is comparable to the amount of chlorine added to municipal drinking water for disinfection purposes.
This amount of chlorine will kill all zebra mussel larvae being drawn into the system. It is also is sufficient to kill all mussel life stages that may already be in the system after a contact time of about three weeks. Continual chlorination will keep the in‑house plumbing free of zebra mussel attachment.
An added benefit of chlorination is that it kills many types of bacteria present in lakes and rivers, improving the potable quality of the water. Homeowners should check with their county health department or Cooperative Extension Service for guide­lines on human consumption of lake or river water.
If homeowners find the taste or smell of chlorinated water objectionable, activated charcoal filters can be placed at the home’s drinking water taps to remove the chlorine taste before it is consumed.
Kills all life stages
Kills many other pathogens
Remove taste with carbon filter 36

37. Filter-Chlorinator Combo
Although a chlorinator will improve the potable quality of the water, it will not prevent shells or shell fragments drawn in from the waterbody from clogging faucets. An inexpensive 60 to 100 micron strainer or filter should be used in conjunction with a chlorinator to remove the most likely threat from zebra mussels.
“Healthier” water
Kills or removes all mussels 37

38. Hand-Driven Shore Well
Pumphouse
Driven pipe
with well point
In some locales, specifically those with a sand and gravel shoreline, an old shoreline residential water source may be ready for a comeback: the shore well. Shore wells utilize the naturally occurring sand and gravel of the shoreline to filter out particulate materials, including zebra mussel veligers. In its simplest form, a shore well consists of a pipe tipped with a well point driven into a sandy shore until the point penetrates into the water table associated with the river or lake. The pipe must penetrate the low water table to ensure a constant flow of water even during drought conditions.
A shore well requires a very sandy shoreline with little or no rock or hardpan in order to allow the well point to be driven to the water table. Shore wells are usually only applicable for low flow systems, such as seasonal or weekend cottages. Shore wells are also prone to bacterial contamination and should not be used for providing drinking water.
Infiltration
from waterbody 38

39. "High Tech" Shore Well
Another approach is to dig a conical well or cistern approximately 6 to 10 feet wide at the top and 2 to 3 feet in diameter at the bottom. It should be deep enough to penetrate at least several feet through the shoreline sediments into the low water water table. A central sleeve of plastic, concrete, or metal is then installed to prevent caving in and to serve as a collector. Water will infiltrate into the collector from the open bottom of the sleeve; the sleeve can also be perforated at the bottom where it penetrates the water table to facilitate water infiltration. The rest of the conical pit around the collector is then filled with sand to facilitate efficient filtration of water flowing into the collector. Zebra mussel veligers and other particles are physically excluded as the water passes through the sand. The cistern should be located far enough landward from the water's edge to place the top of the collector above high water wave runup. This prevents overtopping during storms. To prevent contamination by surface runoff, the cistern casing should have a watertight cover installed and the sand fill should be covered with several inches of compacted clay. A submersible pump can be installed in the collector or a jet pump can be installed in a wellhouse near the cistern, with a pipe running into the collector. 39

40. Shore Well with Infiltration Channel
Shore cisterns generally are not practical in areas with rocky shorelines or with shallow bedrock. In some cases, this problem can be overcome by digging a trench from the cistern out into the lake or stream. The trench should be deep enough to channel water from the source to the cistern even during drought conditions. The trench is also filled with coarse sand and gravel. The entire structure, trench and cistern, is capped with a layer of compacted clay to prevent contamination by overland flow. Local resource management agencies should be consulted to determine the need for permits for either type of shoreline cistern. 40

41. Shore wells and cisterns can remove zebra mussel veligers and other particles. However, they may not provide potable water without the addition of some form of disinfectant due to the possibility of bacterial contamination. This is especially true in areas with agricultural livestock runoff or where septic system leach fields have been placed close to the top of shoreline banks or bluffs. Contamination of the wells could result from infiltration of animal waste or septic leachate into the water table. Homeowners should consult with the county Cooperative Extension Service or health department for information on potable water supplies. 41

42. Drilled Wells The ultimate onshore preventive measure
May not be viable alternative where:
No available aquifer
Sulfurous water
Salty water
Polluted ground water
Perhaps the ultimate onshore preventive measure is the drilling of a traditional well.
However, in areas where homeowners have chosen not to drill a well because of unsuitable water conditions such as…
no available aquifer…
sulfurous or…
salty water…
or polluted ground water…
this may not be a viable alternative. 42

43. Offshore Strainers Use of screens or strainers at intake end of pipe
Effectiveness depends upon:
Mesh size of screen
Size of mussels being drawn into pipe
Common mesh on small intake (1/4 - 1/2 inch) keeps out leaves but not zebra mussel veligers (as small as 70  {3/1000 inch})
Simple screens are ineffective as a zebra mussel control method
The first thing most people think of when considering protecting the offshore component of residential water intakes from being clogged by zebra mussels is using some form of screen at the waterbody end of the pipe to prevent the mussels’ entry into the mouth of the pipe.
The effectiveness of this control method depends upon…
the mesh size of the screen…
and the size of the mussels being drawn into the intake.
The common mesh used over small intake pipes is between one quarter and one half inch, and is intended to keep out pieces of leaves and other large objects. Zebra mussel veligers may be as small as 70 microns, about three one-thousandths of an inch.
Therefore, simple screens are ineffective as a zebra mussel control method. 43

44. Offshore Strainers
Effectiveness can be increased by reducing mesh size
Too small openings can clog quickly with silt, algae, and debris
Screens can become fouled
While the effectiveness of screens could be increased by reducing the mesh size…
making the openings too small could cause the screen to clog quickly with silt, algae, and debris, keeping out water along with the veligers.
Furthermore, since zebra mussels attach to almost any hard surface, the screens themselves could become fouled by the mussels that they’re intended to keep out. This could be minimized by using copper screens, but even the protection afforded by copper quickly loses its vitality as the copper corrodes. 44

45. Offshore Filtration Constructed alternatives Infiltration galleries
Raised fill beds
Manufactured alternatives
Prefabricated sand filters
Ceramic filters
Cartridge filters
There are several construction approaches to the protection of the offshore component of residential water systems. There are also a number of manufactured offshore filters now being marketed in the Great Lakes region.
Constructed filters can be categorized as infiltration galleries and raised fill beds.
Manufactured filters can generally be categorized as prefabricated sand filters, ceramic filters, and cartridge filters. 45

46. Buried intakes or constructed sand filters are used in Europe and parts of North America to prefilter water being pumped into small municipal water supplies with capacities of up to 20 million gallons per day. Such constructed filters can be downsized to handle the water needs of groups of private residences or even single residences, but may be prohibitively expensive when compared with other alternatives. 46

47. Infiltration Gallery
One form of buried intake is the infiltration gallery. This consists of a series of porous intake pipes laid in trenches excavated into the bed of a lake or river. The trenches are then backfilled with sand and gravel and covered over with crushed stone or cobble. The pipes connect into a header pipe, which in turn connects to a pump. Filter cloth around the pipes prevents sand from entering and clogging the pipes. The pump draws water downward through the sand and gravel into the buried pipes. The sand and gravel serve as a filter, blocking the passage of zebra mussel veligers and other particles. Such sand filters need to be constructed with fine enough sand as to provide for a maximum porosity of 40 to 60 microns. The filter bed also tends to have low oxygen, creating a hostile environment that kills many of the trapped veligers. Small infiltration galleries can provide flow rates of up to about one gallon per minute per square foot of filter surface.
Assuming use of a jet pump capable of about 12 gallons per minute, the minimum dimensions for a private residence infiltration gallery capable of providing 250 to 400 gallons per day would be two trenches, each 4 feet long, 4 feet deep, and 2 feet wide. Each trench would have a length of four-inch diameter perforated pipe placed on top of a six-inch layer of gravel and covered by an additional 6 inches of gravel and 3 feet of sand. The gallery would be protected from wave and ice scour by a cover layer of cobbles or large crushed stone. It is good practice to overdesign the filter with a third, and possibly a fourth trench providing an additional 8 to 16 gallons per minute capacity to allow for gradual clogging by fine particles. 47

48. Raised Fill Bed
Another form of intake sand filtration, the raised fill sand filter, eliminates the trenches and replaces them with a shallow layer of gravel placed directly on a lake or river bed, upon which the perforated pipes are then placed. The pipes in turn are covered with a raised fill of gravel and sand, which is then covered with cobbles or crushed stone. This raised fill sand filter functions in the same way that an infiltration gallery functions with water drawn down through the sand and gravel into the pipes, excluding mussel veligers and other particulate material. General dimensions for a residential scale raised sand filter would be 8 feet of four-inch diameter perforated pipe placed on a bed of 6 to 8 inches of gravel, buried 6 to 12 inches deep under gravel, covered by 2 to 3 feet of coarse sand and topped with a protective layer of cobble or coarse crushed stone. As with infiltration galleries, raised fill beds should be over-designed with more pipe and a larger surface area to compensate for gradual clogging. 48

49. Backflushing Offshore Filters
Infiltration galleries and raised fill beds will eventually clog with fine particles
Backflush by pumping water from shore through pipe system to flush out fine particles
Sand beds can become compacted over time
Sand galleries and raised fill beds are subject to eventual clogging by fine materials such as silt, clay, and algae.
In addition to having additional pipes placed to ensure an adequate supply for extreme events, constructed sand filters should be designed so that they can be backflushed by pumping water from the shore through the pipe system to flush fine particles out of the sand.
Furthermore, the sand beds can become compacted by having water pumped through them into the piping system…
leading to cracks in the sand and…
allowing zebra mussel veligers to enter the system.
Periodic backflushing can also help to prevent such compaction and cracking.
Cracks can form in sand
Zebra mussel veligers can be drawn into pipe
Backflushing “fluffs” sand up, prevents cracks 49

50. Prefabricated Sand Filter
A lower cost alternative is the prefabricated sand filter. In this approach, a concrete, steel, or plastic box, with a perforated pipe running lengthwise through it, is filled with course sand, placed into the waterbody, and hooked up to the residence’s intake pipe. A general design would use a container 8 to10 feet in length by 4 feet wide by 4 feet deep. At minimum, 4 to 6 feet of four-inch diameter perforated pipe would be laid in the bottom of the box on a six-inch layer of gravel with another 6 inches of gravel over the pipe. Two to three feet of sand would be placed over the gravel, leaving just enough room at the top of the box to add a layer of cobble or crushed stone. As in constructed sand filters, the pipe should be wrapped with filter cloth to prevent clogging of the pipe by sand. A prudent design would have 8 to16 feet of pipe to allow for some clogging by fine particles between backflushings. Existing concrete castings such as septic tanks and burial vaults could be utilized for the containment structure. Water is drawn through the open top and sand into the pipe, excluding the mussel veligers and other particulate material. Unless the filter is placed in water deep enough to be below stormwave scour, some rip rap should be placed around it to prevent undermining or shifting. This type of filter should be less expensive to construct than infiltration galleries or raised fill beds. As with constructed sand filters, prefab filters should be designed with backflush capability. 50

51. Manufactured Offshore Filters
Homeowners should investigate the product
When, where, how long, under what conditions have filters been field tested?
Names of clients with filters in water for reasonable length of time
What happens if system clogs prematurely?
Is automatic backwashing available as option?
A number of much smaller commercial prefabricated sand filters have now been on the market since the mid-1990s.
They utilize the same design components as constructed sand filters: drawing water through a sand filter media into some form of perforated pipe or well screen.
Homeowners considering purchasing such filters should ask the sellers…
to provide information on when, where, how long, and under what conditions the filters were field tested…
names of clients who have had the filters in the water for a reasonable length of time…
and what the seller will do in the event that the system clogs prematurely. Product testing should have been during the spring through fall seasons when mussel veligers and algae are in the water and turbidity from surface runoff is at its highest, not in the winter when there is little or no threat to intakes.
Most commercial filters are now designed to be backflushed. Buyers should consider whether they want to spend the extra money for automatic backflushing or save money with manual backflushing that requires remembering to perform the function on a regular periodic basis. 51

52. Offshore Filters and Water Potability
Offshore sand filtration can remove zebra mussels and other large particles
By itself, offshore filtration is not intended to provide potable (drinkable) water
Additional treatment by chlorination or ultraviolet light needed to kill bacteria
Consult county Cooperative Extension Service or health department about drinking water standards
While in‑the‑lake sand filtration should successfully remove zebra mussels and other large particles…
it by itself is not intended to provide potable water.
Additional treatment at the house by either chlorination or use of ultraviolet light may still be needed to kill bacteria.
Homeowners should consult their county Cooperative Extension Service or health department for more information. 52

53. Environmental Impacts of Constructed Offshore Filters
Turbidity during excavation and backfilling impacts local water quality temporarily
Use trenching equipment rather than backhoes
Use silt screens around excavation site
Disturbance of natural lake or river bottom habitat
New habitat provided by stone cover material
Prefabricated sand filter minimizes habitat loss with smaller disturbance “footprint”
Possible environmental impacts of constructed in‑the‑lake sand filters include:
the temporary degradation of localized water quality due to an increase in turbidity during excavation and backfilling, the disturbance of natural lake or river bottom habitat during construction, and a change in bottom habitat type from natural to human‑influenced substrate.
Turbidity impacts can be mitigated through the use of:
trenching equipment rather than backhoes to dig the trenches…
and through the use of silt screens around the excavation site.
The habitat impacts may be partly offset by providing new bottom habitat in the form of the stone cover material.
The prefabricated sand filter may minimize loss of bottom habitat impacts by having a smaller disturbance footprint than infiltration galleries or raised filter beds.
Remember, all constructed and most commercial sand filters will almost certainly require permits from state or local natural resource management agencies.
Permanent change in bottom habitat type from natural to human-influenced substrate 53

54. Offshore Ceramic and Cartridge Filters
Abrasive ceramic filter media removes or destroys mussel veligers
Cartridge filters trap particles, including zebra mussel veligers
Porosity should be small enough so that no mussel life stages will pass live into intake pipe
Available with manual or automatic backwash
Should ask how often the filter media needs to be replaced or cleaned
Several ceramic and cartridge filters intended for use on the intake end of the pipe are now on the market.
These filters use either a very abrasive ceramic filter media to remove or destroy mussel veligers…
or contain some other form of media to trap particles in the water flowing through the filter.
Homeowners interested in these products should ascertain how long they have been in service in mussel-infested waters, what the porosity is, making sure that it has small enough openings that no life stages will be passed live into the intake pipe…
how often the filters need to be backwashed
some need to be manually backwashed, some are automatic…
and how often the filter needs to be replaced. 54

55. Nonfouling Pipe Materials
Copper or galvanized intake pipes
Discourage zebra mussel attachment
Lose effectiveness as they corrode or oxidize
Should be augmented by other methods
Homeowners might also consider the use of copper or galvanized intake pipes…
both of which discourage zebra mussel attachment.
Because zebra mussels will attach to corroded or oxidized copper or galvanized surfaces, use of such material for pipes will not serve as a primary control method…
and should be augmented by other methods, as well. 55

56. Periodic Cleaning of Offshore Component
Allows some clogging by mussels, followed by periodic maintenance
Cleaning
Mechanical
Thermal
Pipe replacement
Another approach to controlling zebra mussels in the offshore component is to allow a certain amount of clogging in the intake pipe followed by periodic maintenance.
Such as cleaning, using mechanical…
or thermal techniques…
or replacing the pipe.
Before selecting this alternative, however, homeowners should ensure that the onshore component is protected by its own on-shore filtration or chlorination system.
To facilitate mechanical or thermal cleaning of an intake pipe, it is advisable to install a cleanout or “Y” connection at the shore end of the pipe.
Protect onshore component with its own system
Install “Y” connection cleanout at shore end of pipe to facilitate cleaning 56

57. Periodic Cleaning of Offshore Component
Plumber’s snake for short pipes with easy access
Loosened mussels must be removed by:
Pumping through a strainer at the pump
Opening foot valve and backflushing
Not possible in pipes with:
For short pipes that have easy access from the shore end, cleaning could be as simple and low tech as periodically running a plumber’s snake through the pipe.
Once the pipe is snaked, loosened mussels are removed by pumping the pipe at a high flow rate through a strainer at the pump…
or by opening the foot valve and backflushing the pipe into the waterbody. This method is not effective in pipes where the infestation is so great that the amount of dislodged mussels might obstruct the snake.
Snaking is also not usable for pipes with tight bends, check valves, or radical diameter changes.
Tight bends
Check valves
Radical diameter changes 57

58. Oxygen Deprivation
Zebra mussels “breathe” oxygen as water passes over their gills
Seal both ends of pipe long enough for water to lose all of its oxygen
Oxygen demand greatest in warm water
Oxygen deprivation most effective in summer
2 to 3 days anaerobic water at 74º F = 100% kill
Most suited to weekend cottages that routinely have water system shutdowns
Year-round homes will need second intake
Because zebra mussels breathe oxygen as they draw water over their gills, oxygen deprivation…
accomplished by sealing off pipes long enough for the water to lose all of its oxygen, can also be used as a control method.
Mussels’ demand for oxygen is greatest in warm water.
Therefore, oxygen deprivation tends to work best in summer.
Two or three days exposure to anaerobic water at water temperatures above 74 degrees Fahrenheit should result in 100% mortality.
Since any pipe treated in this manner must be able to be shut down and sealed for a number of days until the oxygen and food supplies are used up, this alternative would be most suited to weekend cottages that routinely have such shut downs.
To use this strategy in year-round homes, a second intake pipe could be added, allowing one pipe to be closed down for cleaning while water is pumped through the second. 58

59. Removable Intake Pipes
Weekend cottage: low water demand & not for drinking
Single short flexible plastic pipe directly on lakebed
Pull from water - leave on shore - dry in sun
Dead mussels “snaked” from pipe
Replace into water next weekend
Several times a season based on speed of fouling
Dual short flexible plastic pipes
Pull one-at-a-time from water, leave on shore, dry in sun, and clean
Pumping continues through second pipe
Onshore piping protected by onshore filtration
For a weekend cottage using only small amounts of water for non‑potable uses…
a practical control strategy might be the use of a single, very short flexible plastic pipe placed directly on the bed of the lake.
Such a pipe could be disconnected, pulled from the water, and laid on the shore at the end of the weekend. Drying in the sun during the week would kill any mussels in the pipe.
The dead mussels could be snaked from the pipe…
before it is replaced the next weekend.
This would need to be performed several times a season, based upon how quickly the pipe becomes fouled.
A slightly upgraded version for cottages with low water demand is the installation of dual short flexible plastic pipes.
When one pipe becomes clogged, it is pulled from the waterbody, allowed to dry completely in the sun for several days, and cleaned…
while pumping continues through the second pipe.
In either of these alternatives, the onshore piping needs to be protected by onshore filtration. 59

60. Thermal Treatment Periodic flushing with hot water
90º F for about 1 hour = 100% kill
> 130º F = immediate kill
Foot valve must be open to allow flow of hot water
Cold lake water is heat sink - need enough hot water to fill pipe and keep hot long enough for kill
Another effective and environmentally sound method of controlling zebra mussels in intake pipes is periodic flushing with water heated to…
90 degrees Fahrenheit or hotter for about one hour to ensure 100% mussel mortality.
Water temperatures greater than 130 degrees will result in almost immediate death of most mussels.
In order to treat a pipe with heat, the foot valve must be able to be opened so it does not restrict the flow of water down the pipe from the shore.
The source of hot water needs to be large enough to provide sufficient heated water to fill the entire pipe with hot water and keep it at that temperature long enough for an effective treatment.
Because the discharge of large amounts of heated water into a waterbody could have locally negative environmental impacts, local resource management agencies should be consulted to determine whether the amount of hot water that might be discharged into the waterbody would require a discharge permit.
The dead mussels will remain attached to the inside of the pipe for several days and must later be removed by backflushing or by pumping the pipe at a high rate of flow.
An alternate heat treatment would employ the use of a portable steam generator. The generator is set up at the shore end of the pipe and has a long feed hose, which is sent down the pipe and through the cleanout “Y” recommended earlier in this presentation. This allows treatment of the inside of the pipe with live steam, and results in less hot water discharge.
Such systems have been employed in New York’s Finger Lakes in pipes up to 200 feet in length. The more often the pipe is heat treated, the smaller the number of dead mussels to be removed.
Hot water discharge = negative environmental impact
Dead mussels must be removed by backflushing
Portable steam generator from shore end of pipe
Live steam = instant kill
Less hot water discharge 60

61. Chemical Treatment
No environmentally sound chemical treatment system for offshore part of residential water intakes
Never pour or backwash chemicals down intakes
Environmentally harmful effects on fish, zooplankton, and bottom-dwelling invertebrates
Might be harmful to human health
Could be illegal if discharged into surface waters
Not effective in killing zebra mussels due to short contact time afforded in a residential intake pipe
You may have heard that public drinking water treatment facilities are using chlorine or other oxidizing chemicals to control zebra mussels in their intakes.
Unfortunately for homeowners, at this time there are no reliable and environmentally sound chemical treatment systems suitable for use in the offshore component of residential water intakes.
Homeowners should not under any circumstance pour or backflush any chemicals down their water intake pipes.
Such chemicals might be environmentally harmful. There is great concern for potential negative effects of chlorine or other chemicals on nontarget species such as fish, zooplankton, and bottom-dwelling invertebrates in lakes and rivers.
The chemicals also might be harmful to human health…
illegal if discharged into surface waters…
and might not be effective in controlling zebra mussels given the short contact time afforded in a residential intake pipe. Before using any chemical treatment method, homeowners should check with their local environmental regulatory agencies to determine whether this would be legal in their area. 61

62. Deeper Intakes Deep water intake might minimize colonization
Water too cold
Insufficient food supply
Zebra mussels survive near-freezing Great Lakes winters with little damage below ice scour zone
Veligers found down to about 200+ feet
Cost of very deep intakes prohibitively expensive
If waters below thermocline become oxygen depleted, sub-thermocline intakes could minimize colonization
Some people have advocated moving residential intakes to deeper water in the hopes that…
deeper water will be too cold for zebra mussel colonization…
and will not have sufficient food supplies to support large numbers of mussels.
Theoretically this might be true, but zebra mussels survive the near-freezing water temperatures of Great Lakes winters with little damage to established colonies below the ice zone.
Zebra mussel veligers have been found at depths down to about 200 feet in Lake Ontario.
For residential systems, the cost of extending intakes that far would be prohibitively expensive.
Many lakes thermally stratify or layer during the summer months. The layer that separates warmer surface waters from colder deep waters is called the thermocline. If there’s an abundance of decomposing organic matter below the thermocline, the deeper, bottom waters of stratified lakes can become oxygen depleted. Because zebra mussels need oxygen to survive, it is possible that water intakes in these oxygen-poor waters could remain relatively mussel free. 62

63. Multi-Residence Systems
Most control alternatives can be scaled up to meet needs of multiple residences
Cost per residence could be lower than for single residence systems
Multi-residence systems help eliminate proliferation of smaller, less efficient individual systems
Might be more environmentally sound
Most, if not all, of the alternatives described in this presentation could be scaled up to meet the needs of more than one residence.
The per-residence cost of installing such multi-residence systems could be lower than for homeowners going it alone.
Multi-residence systems, which would help to eliminate the proliferation of smaller, less efficient, and possibly poorly installed individual systems…
might also benefit the environment. 63

64. An ultimate societal solution to the problem of zebra mussel fouling of residential water systems might be the extension of public water to those areas adjacent to but not already part of public water districts. 64

65. Written and Produced By
Charles R. O’Neill, Jr.
New York Sea Grant
2001