HATCHERY REQUIREMENTS 31 



ground; winter storage at northern hatcheries may be a problem, however. 

 If transportation is available, or on-site mechanical separators and vacuum 

 filters can be justified, the sludge can be reduced to moist cakes and sold 

 to commercial fertilizer manufacturers; some municipal sewage plants 

 dispose of sludge this way. 



Alternatively, if the hatchery is near an urban area, it may be possible to 

 dispose of solid waste in the municipal system. Incineration of sludge is the 

 least desirable means of disposal, as dewatering and drying the material is 

 costly, and the process merely exchanges air pollution for water pollution. 



Figure 14. Sludge is collected from the linear clarifiers into storage lagoons at 

 the Jones Hole National Fish Hatchery, Utah. The lagoons are periodically 

 dewatered and the sludge dried for removal. 



