Help for Mariah

[rmasongo]

Members hope you are all doing well this year. Please see below a message from Mariah who is implementing a project in Mozambique. anyone with an experience to this unique situation please help her. 

Hello Robinson,

Thank you for adding me to the ABINET group! Right now my main question is,  what are other practitioners doing with the silt that results from washing the sand and gravel? I don't have a good system of collecting and disposing of it. 

My other problem is that even with our best efforts, most of our filters have thin cracks and general leaking toward the bottom of the filters. We tried various sources of sand with various quantities of dust in them, taking out all the organic material we possibly can, sticking the trowel in the wet cement around the base of the filter (one of the last steps of pouring the cement) to get it compact and get the air out. And we tried reducing the amount of water in the cement mix. 

I am pioneering a biosand filter project as part of a larger community development/ WASH project. We are part of an association near Gondola, Mozambique called Africa 180. I'm doing the version 10 (no ledge) concrete BSF. 

Thanks again!

Mariah McGlothlin

Associação Missão Africa 180˚    

[TAUZEN TEMBO]

 

Hi Robinson Masongo,

We are fine.

Thank you for the issue at hand of Mariah in Mozambique.

The issue of silt is something one cannot avoid as long as they are washing filtration sand.

It would be helpful if some form of platform(washing bay) is put in place (for easy collection of silt).

The above will depend on the method being used when washing (is it by hand or machine ?)

Disposing of silt is another challenging issue and if not properly done can negatively affect the environment ( e.g. causing siltation of streams and rivers). One simple option could be to use the silt to fill ditches, pits in the surrounding areas.

 

The issue of having cracks, (usually leaking toward the bottom of the filters). It seems you have done most of the things you needed to do to address the cracking. You can as well look at the mold (inner and outer) and is the demolding done when the filter is still green? It is also important to look at the weather (especially if it is hot), the drying of the concrete should not be very fast.

In general, Quality assurance is very important.

 

Hope to hear of the best solution for your project,

 

Tauzen Tembo,

 

Client Consulting Manager, AFMAC

Seeds of Hope international Partnerships (SHIP)

 

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[Mariah McGlothlin]

Hello Tauzen

Thank you for your advise! All very helpful. We will try waiting a longer before demolding the filters, and keeping them cooler and wetter  while in the mold. 

I recently checked on those filters with fine cracks, which we tried to fill in with cement paste. We kept them full of water for several weeks, and at first they leaked constantly. But now they seem to hold the water and I don't see water collecting under/around the filters anymore. They seemed to improve over time. 

I hear you on the silt. Looks like we've got to get creative with how to dispose of it. 

Thanks again!

Mariah