Here is also now the video from the presentation by Jess on "To Seal or not to Seal: Simplifying Bangladesh’s latrine pit debate through the FilTo Innovation":



Or jump to time 39 min 30 s here:



You can listen to the questions and answers afterwards as well (at around 53 minutes), including Eddy Perez, Steve Sugden and others

And you can see me in this video, too, as I was the chair person.

How about using an industry standard FIBC sack?
en.wikipedia.org/wiki/Flexible_intermediate_bulk_container
Could be helpful to transport the sand to the site and then be used as an outer shell that is water permeable but keeps the sand in place.

Thank you for your suggestions!

One of the biggest challenges in Bangladesh is that there is water everywhere. It is very difficult to keep water separate from systems and to keep it from pooling around latrines. Almost the entire country floods yearly. You can see in the picture that Elisabeth posted below what the area looks like in the rainy season. All the guide books say not to install latrines near water, but that is virtually impossible in most of country.

We currently have a mesh layer that separates the sludge and the sand and one option is to use two layers of mesh. We are trying to limit the amount of sand and sewing required. Sand is quite expensive and any sewing means that we can't quality control the installations as well and it is difficult to maintain continuity.

Dear Jess,

Thanks for your post on 1 April about your presentation at FSM3. I think you forgot to provide the link to your presentation. It is this one:

To Seal or not to Seal: Simplifying Bangladesh’s latrine pit debate through the FilTo Innovation: Jess MacArthur, iDE, Dhaka, Bangladesh
www.susana.org/images/documents/07-cap-d...3-3-1-3MacArthur.pdf

Here is one photo of Jess's work in Bangladesh:



Regards,
Elisabeth

Some thoughts:

Similar to what Krischan just suggested, maybe extending the concrete rings down to the brick chips and sand layer could help preventing the surrounding soil to flush excess water into the sand layer and create preferential flow paths there during the monsoon season. This, however, would reduce the area of the infiltrative surface into the soil and would need to be considered, I guess.

Also, particular care could be given to prevent ponding during heavy rainfalls around the structure and not to create preferential flow along the outer sides of the concrete rings by proper back-filling during installation and extension of the concrete seal well above the ring diameter.

Is this similar to "sand enveloped pit latrines"? As described here:
knowledgepoint.org/upfiles/14224596638193196.pdf

Maybe a layer of woven plastic fabric (could be stitched together from old sacks) could be used to envelope the sand to avoid the channel formation?

Hello forum,
In January I presented at the FSM3 Conference in Hanoi about some research that iDE-Bangladesh is doing in the southern tidal zones of the country around pit infiltration and safe leaching. We have been testing an in-hosue innovation called the FilTo which forces leaching through a layer of sand.

The FilTo worked perfectly until after the monsoon, when receding water began to channel out holes around the leaching areas right through the sand layer, effectively bypassing the sand filter.

We have been testing the FilTo by syphoning effluent off the bottom of the sand layer below the FilTo.

I would love to hear your suggestions of how to improve this technology and how to avoid the post monsoon issues.

Please do not try and implement this in your working areas yet. Once we get a version that works, I will happily share, but we aren't quite there yet.