Fish Hatchery Management - fisheries & aquaculture

HATCHERY REQLIIREN,TINTSWASTE WATERSOLIDSR EM OVALAM MON IAAERATIONI I I IiR ECON DITIONWATERFIcURF; 9. Schematic diagram of ion exchange removal ofammonia from hatcherv waste water.o t'HER AMMONTA REMOVAt. ]'ECHNt(2UESSeveral procedures for removing ammonia from hatchery water have beentried. Many of them work, but are impractical in most circumstances.When the pH of water is raised to 10 or 11 with calcium or sodium hydroxide,most of the ammonia goes to the gaseous form (NH1) and will dissipateto the air if the water is sprayed in small droplets. This ',ammoniastripping" does not work well in cold weather, and the water has to bereacidified to normal pH levels.Chlorine or sodium hypochlorite added to water can oxidize g5-ggli, ofthe ammonia to nitrogen gas (Figure 10). "Breakpoint chlorination" createshydrochloric acid as a byproduct, which must be neutralized with lime orcaustic soda, and residual chlorine must be removed as well. This is anuneconomical process, although future technological advances may rmprove