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Mark,

I have just had a look at the LaDePa and agree that it will not be suitable, not on economic grounds, just that it will not be technically viable in any case due to the likely content of plastics and other hard solids that will need to be screened out and the need to get to a solids content of 20 - 35% before the sludge can be pelletised.

There is a manual on faecal sludge management published by IWA and SANDEC which you can download here: https://www.eawag.ch/en/department/sandec/publications/faecal-sludge-management-fsm-book/

My first thought is that you should consider vegetated sludge beds, which are covered in the publication. These have been used successfully in Denmark and SANDEC have done some work in Africa which is encouraging. You would have to line the beds if it is necessary to prevent pollution of the ground water (but the pit latrines will be doing this anyway I assume) and you will need to treat the underdrainage. If you use ponds for this, again they would need to be lined.

The problem with the lining is that after a number of years you will have to remove the accumulated sludge and this would risk puncturing any membrane, but you should be able to design some protection to the drainage layer and membrane to minimise this risk.

I have just had a look at the LaDePa and agree that it will not be suitable, suitable - not on economic grounds, just that it will not be technically viable in any case due to the likely content of plastics and other hard solids that will need to be screened out and the need to get to a solids content of 20 - 35% 20-35% before the sludge can be pelletised.

There is a manual on faecal sludge management published by IWA and SANDEC which you can download here:

https://www.eawag.ch/en/department/sandec/publications/faecal-sludge-management-fsm-book/

My first thought is that you should consider vegetated sludge beds, which are covered in the publication. These have been used successfully in Denmark and SANDEC have done some work in Africa which is encouraging. You would have to line the beds if it is necessary to prevent pollution of the ground water (but the pit latrines will be doing this anyway I assume) and you will need to treat the underdrainage. If you use ponds for this, again they would need to be lined.

The problem with the lining is that after a number of years you will have to remove the accumulated sludge and this would risk puncturing any membrane, but you should be able to design some protection to the drainage layer and membrane to minimise this risk.