A simple answer: Sludge that ...

A simple answer: Sludge that is low in VLSS can be diverted to "reed Bed systems." Where the water percolates through the rhizome zone of various species of reeds, e.g. Vertiver grass, Phragmities australis, etc. Reeds selected must be indigenous to the region, and that they have the ability to metabolizes contaminants through their root structure. Not to be confused with "Constructed Wetlands" which handles the wastewater and the sludge gets diverted to the Reed Beds--they are separate and distinct.  Once the VLSS has been reduced in the sludge it can be harvested as a soil amendment depending on local regulations and quality of the residuals as a biosolid, and in some cases the reeds can be used as animal feed. This is the low energy approach to using sludge for beneficial reuse applications. You do need to have land avilable.