Alternate Control Strategy for Dreissinids Using Electrical Methods
Since the discovery of zebra mussels in the Laurentian Great Lakes in 1986 on natural gas well head and well
markers, zebra and quagga mussels (Dreissena spp.) have spread across large areas of the continental United
States. In industrial systems, control of Dreissena spp. biofouling has primarily concentrated on oxidizing and nonoxidizing
chemicals. However, chemical treatments are usually not viable options in Reclamation facilities. There is a
need for economical and environmentally safe control strategies for these major biofouling mussels in Reclamation
raw water delivery systems. Alternative methods utilizing electricity has been shown to impact mussel behavior,
including mortality and a reduction in the rate of byssogenesis (byssus attachment). Methods include electrified fields
which inhibited passage of live veligers (larval life stage) and electrical currents which prevented attachments to
metallic surfaces. This project proposes to carry out well established electrical testing procedures to investigate the
effectiveness of electrical control methods under field conditions similar to those found in Reclamation facilities.
The goals of this project are to determine and compare the electrical dosage and electrical power consumption of AC
and DC applied at different waveforms (sinusoidal AC, squared DC, cycle rates, etc.) to induce quagga mussel
mortality and inhibition of byssogenesis in the raw water parameters typically found in Reclamation facilities on the
Lower Colorado River (LCR). Electrical dosage or power density can be determined by the measured ambient
conductivity and the applied voltage gradient. Electrical power (watts) can be calculated by Ohm's Law from the
voltage applied and the resistance. The electrical power consumption can then be obtained by dividing the product of
wattage and exposure duration by a normalized conversion factor that will allow direct comparison of power
consumption of different electrical waveforms. Th
Need and Benefit
Reclamation reservoirs in four of the five Reclamation regions (GP, UC, LC, and MP) are currently infested.
Reclamation has a need for an effective, economical, and non-polluting management control programs that managers
to minimize or eliminate the threats these mussels pose to the operation and maintenance of Reclamation water
systems. Mitigation of the threat the zebra and quagga mussels impose currently can be accomplished primarily by
one of two means, chemical treatment and mechanical removal. Chlorination is considered to be the most effective
and popular method of chemical control. Like most chemical controls, it can be utilized as either in a proactive or
reactive control strategy. However, chlorination is a broad-spectrum chemical biocide and a powerful oxidant.
Chlorination is also becoming increasingly more regulated and may eventually be banned by individual states and/or
the federal government. Salt treatment (i.e. KCl) has been used successfully to eradicate zebra mussels from a water
body. However, the cost of the most common source of this chemical, muriate of potash, has increased more than 5
folds within the past few years (> $1,000/metric ton). To be effective, a large amount of potash would be necessary to
maintain the optimum lethal concentration level (typically 100 ppm) in a body of water for a sustained period of time.
Application of molluscicides (i.e., quaternary ammonium compounds) into water systems is of concern for the health of
aquatic ecosystems, especially when threatened or endangered mussel species are present. Among mechanical
treatments, filters (sand, mechanical) are probably the most popular proactive strategies for protecting the entire water
delivery system by installing the filters at the system intake. Other mechanical possibilities include UV exposure,
acoustics, antifouling coatings, and thermal treatment. On large water systems, the retrofit required may be expensive,
difficult to implement, may not be 100% effective, and for some mechanical treatment, can cause an unacceptable
drop in flow or pressure in the system. Extreme hypoxia (lack of oxygen) can be a very effective method of
eradication. However, hypoxia may not be feasible for some confined water (conduits) where water is continually
mixed and flowing.
Therefore, the development of non-chemical or environmentally-friendly control methods for managing zebra and
quagga mussel infestations is warranted. Carbon dioxide alone have been used to prevent attachment and induce
mortality. It is also used as a narcotic in combination with other treatments (i.e. chlorination) to lessen the length of
time for complete mortality. The use of various electrical waveforms to shock or kill zebra mussels have been
investigated since the early 1990's, soon after the discovery of zebra mussels in the United States. Previous research
to control zebra mussels using electrified fields focused on preventing settlement in water conveyance systems. The
research has shown that zebra mussel veligers can be stunned and/or killed using pulsed-power systems. More
recently, electrical currents were applied to cause detachment of adult mussels.
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