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Can carbon dioxide be used as an environmentally neutral molluscicide for mitigation of zebra and quagga mussel macrofouling? Carbon dioxide 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 bioavailability 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.

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.