Although varied somewhat, each of the SPTs I’m interested in use a batch approach and age either an aerobically or anaerobically digested sludge in either a lagoon or in the case of a cake, separate piles. Once sufficiently aged, (generally about two years) the sludge is then spread onto a paved surface where it is windrowed and periodically agitated until it reaches a TS of ~65%. 

I’ve now read several papers (available upon request) on this SPT and would like to invite further discussion on the process. 

Advantages 

• Low/moderate capital costs  
• Low operations and maintenance requirements  
• Low energy costs  
• Low noise potential  
• Beneficial reuse options  

Disadvantages 

• Moderate/high land requirements 
• Moderate odor potential