Final Report: Nontoxic Sparker Control of Zebra MusselsEPA Contract Number: 68D01040
Title: Nontoxic Sparker Control of Zebra Mussels
Investigators: Schaefer, Raymond B.
Small Business: Phoenix Science and Technology Inc.
Project Period: April 1, 2001 through September 1, 2001
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2001) RFA Text | Recipients Lists
Research Category: Watersheds , SBIR - Water and Wastewater , Small Business Innovation Research (SBIR)
Description:Following its inadvertent introduction in Lake St. Clair in the late 1980s, the zebra mussel (Dreissena polymorpha) quickly spread throughout the Great Lakes and into many inland lakes, rivers, and canals. Because the zebra mussel tolerates extreme crowding, it clogs intake pipes, filters, trash racks, and other components of ships, dams, pumping plants, and hydropower facilities that use freshwater and has become a serious problem. Chlorine injection effectively controls zebra mussels, but also produces toxic byproducts, some of which are carcinogenic. Furthermore, regulatory actions in the United States and Canada may reduce or eliminate chlorine for controlling zebra mussels. This Phase I project, combined with work supported by the U.S. Army Corps of Engineers, demonstrated the feasibility of using high-intensity pressure pulses from sparkers for the nontoxic, low-cost control of zebra mussels.
Sparkers work by releasing stored electrical energy between two submersed electrodes, producing a high-intensity pressure pulse that can either clear away mature zebra mussels by interfering with feeding or inhibit young zebra mussels from attaching to surfaces. In the control concept investigated in this project, a sparker source is tethered near the entrance to a pipe that is to be kept free of, or cleared of, zebra mussels.
A sparker was introduced in 1992 by another company, but has seen little use because of electrode maintenance issues, and cost, and because scientific data establishing its effectiveness were lacking. In this project, the feasibility of developing a new low-cost and low-maintenance sparker was investigated experimentally in laboratory tests. Also, field tests were conducted in which test samples were placed in water intake pipes during a zebra mussel growth season, and pressure pulses from the sparker were measured for correlation with zebra mussel response. These field tests were the first that combined zebra mussel response tests with measurements of sparker pulses at the locations of test samples.
Summary/Accomplishments (Outputs/Outcomes):Field tests conducted by Phoenix Science & Technology, Inc., at two sites on Lake Champlain, NY, showed that sparker pressure pulses generated near the exit of water intake pipes prevented growth of new zebra mussels for approximately 125 feet into the pipes. Also, the test results showed adult zebra mussels being cleared away for approximately 50 feet into the pipes. The pressure levels and corresponding acoustic spectra producing these effects on the zebra mussels also were measured. In addition, the propagation of the pressure pulse in the pipe showed effects associated with pipe cutoff frequencies and the fundamental frequencies of the sparker pulse.
Laboratory tests showed that the sparker currently in use is inefficient. A new sparker design will have an efficiency of more than a factor of 10 higher than the current sparker. Also, new electrodes were tested, which have a lifetime that is four times longer than the electrodes in the current sparker. A new sparker system with high efficiency and new electrodes will operate for at least 1 year before needing electrode replacement instead of every 5 weeks, as in the current sparker.
A new prototype sparker system for zebra mussel control was designed, with an estimated capital cost of approximately 40 percent less than the current commercial sparker. Also, maintenance costs will be reduced because of increased electrode lifetime. The cost of the new sparker system will be less than that of chlorine injection systems, which will promote commercialization.