24 



FISH HATCHERY MANAGEMENT 



CHLORINE 



WASTE SLUDGE 



NITROGEN GAS 



CHLORAMINES, 

 EXCESS CHLORINE 

 AND DISSOLVED 

 ORGANICS 



AERATION 



RECONDITIONED 

 WATER 



Figure 10. Schematic diagram of breakpoint chlorination remov- 

 al of ammonia from hatchery waste water. 



its practicality in hatcheries. An advantage of this system is that all treated 

 v^ater is sterilized. 



Oxidation ponds or lagoons can remove 35-85% of the ammonia in 

 v^astewater through microbial denitrification in the pond bottom and 

 through uptake by algae. This method requires considerable land area and 

 extended retention time of the wastewater in the lagoon. Oxidation 

 lagoons work best in southern chmates. Cold weather significantly reduces 

 biological activity. 



ESTIMATION OF AMMONIA 



Because of the importance of ammonia to fish production total ammonia in 

 hatchery water should be measured directly on a regular basis. However, 

 rough estimates of total ammonia can be made from an empirical formula, 

 if necessary. Although ammonia can be contributed by source water and by 



