Alternate Control Strategy for Dreissinids Using Carbon Dioxide
Project ID: 1367
Principal Investigator: Kevin Kelly
Research Topic: Invasive Species
Priority Area Assignments: 2013 (Zebra and Quagga Mussels), 2014 (Zebra and Quagga Mussels)
Funded Fiscal Years: 2013
Keywords: carbon dioxide, zebra mussel, quagga mussel, dreissinids
Can carbon dioxide be used as an environmentall neutral molluscicide for mitigation of zebra and quagga mussel macrofouling?
There is a pressing need for new economical and environmentally safe control strategies for zebra mussels and quagga mussels in Reclamation dam facilities. Zebra and quagga mussels are major macrofouling species of water delivery systems and control typically involves manual scraping, thermal treatment, deoxygenation, or biocides. The costs of control and system damage in the United States alone have been estimated at $1 billion/year.
A draft paper "An Initital Assessment of Carbon Dioxide as an Alternative Control Strategy for Quagga and Zebra Mussel Biofouling" has been uploaded into PropC in 2011. This describes in more details the feasibility of using carbon dioxide. This "white paper" is currently going through peer review and visual identity. Once available, the reviewers are strongly encouraged to read this white paper.
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 will allow 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/nonchemical cleaning.
Due to a lack of options, 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 increasily 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. Among mechanical nonchemical 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/nonchemical possibilities include UV exposure, acoustics, antifouling coatings, and thermal treatment. On large water systems, the retrofit required is expensive relative to carbon dioxide, may be difficult to implement, may not be 100% effective, and for some mechanical/nonchemical 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. For example, no zebra mussels
could be found below approximately 30 feet at San Justo Reservoir (CA) due to annual reservoir stratification, despite at least several years of infestation. However, hypoxia may not be feasible for
some confined water (conduits) where water is continually mixed and flowing.
CO2 is a natural chemical that does not require a separate or specialized production (e.g. fermentation), is already produced in large quantities, is recycled from initial combustion waste streams for good environmental stewardship, has an indefinite shelf life, nonflammable, is easy to handle and store, does not require electrical or mechanical power to deliver, and can be distributed easily and evenly in water, including hard-to-reach confined water. Through the carbonic acid/bicarbonate buffer, the change in pH of the water is limited. Addition of carbon dioxide also reduces the bioavailibility of calcium in the water, thereby inhibiting shell growth. Only species that has taken up residence in the confined water (i.e. Dreissinids) would be exposed long enough to reach mortality levels. Once the water is freely exposed to the air at the outlet, purged, or the CO2 is stripped and reused, equilibrium is quickly re-established and PCO2 goes back to ambient pressure, so that it will not affect the downstream water ecology.
Unlike other inventions to control Dreissena species, the patent for the use of carbon dioxide as a control agent for invasive species (No. 6,821,442) is owned by the United States of America as represented by the Secretary of the Department of the Interior. This invention may be manufactured and used by or for the Bureau of Reclamation for government purposes without the payment of any royalties.