Development of a Carbon Filter System for Removing Malachite Green from Hatchery Effluents

Abstract

The US Fish and Wildlife Service was granted an investigational New Animal Drug permit by the US Food and Drug Administration for the use of malachite green as a fungicide at selected state and federal fish hatcheries. However, the permit required that the fungicide be removed from all treated water after March 1989. A study was designed to (1) determine the type of filter and kind of carbon that was most efficient for removal of malachite green and (2) demonstrate that carbon filters can be used to remove malachite green from water used for egg incubation or to hold adult salmon before spawning. Minicolumn simulation studies showed that 8 {times} 30-mesh granular carbon was effective for continuously removing malachite green from water for 230 d at a flow rate of 500 gal/min and for only 62 d at a flow rate of 1,000 gal/min. The removal capacity at the slower flow rate was 1.1 oz of malachite green per pound of carbon. A filter system that contained 20,000 lb of activated carbon in each of two chambers was effective for removal of malachite green from treated water in adult salmon holding ponds at flows of 500 gal/min (6.4 gal/min permore » ft{sup 2}) and greater. The removal efficiency was 99.8% after 105 h of operation, and the adsorption capacity of the system was projected to be sufficient for 20 or more years of routine hatchery operation. A filter system that contained 2,000 lb of activated carbon in each of two chambers was effective for removal of malachite green from treated water in salmon egg incubation units at the designated flow rate of 50 gal/min (4.0 gal/min per ft{sup 2}) and also at faster flow rates. Removal efficiency decreased only slightly for faster flows in both filter systems, and the efficiency improved when treated water was passed through two filter chambers in series.« less