HATCHERY REQUIREMENTS 



23 



WASTE WATER 



SOLIDS 

 REMOVAL 



CLINOPTILOLITE 

 BED 



T 



AERATION 



BRINE 



I 



BRINE 



REGENERANT 



RECOVERY 



AMMONIA 



RECONDITIONED 

 WATER 



Figure 9. Schematic diagram of ion exchange removal of 

 ammonia from hatchery waste water. 



OTHER AMMONIA REMOVAL TECHNIQUES 



Several procedures for removing ammonia from hatchery water have been 

 tried. 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 hy- 

 droxide, most of the ammonia goes to the gaseous form (NH^) and will dis- 

 sipate to the air if the water is sprayed in small droplets. This "ammonia 

 stripping" does not work well in cold weather, and the water has to be 

 reacidified to normal pH levels. 



Chlorine or sodium hypochlorite added to water can oxidize 95-99% of 

 the ammonia to nitrogen gas (Figure lO). "Breakpoint chlorination" creates 

 hydrochloric acid as a byproduct, which must be neutralized with lime or 

 caustic soda, and residual chlorine must be removed as well. This is an 

 uneconomical process, although future technological advances may improve 



