Using a double vault vermi-digesters for single households (max 10 people) in high density areas of Lusaka?

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Re: using a double vault vermi-digesters for single households (max 10 people) in high density areas of Lusaka?

Hi Dean,

Sorry, I misunderstood your sketch in the previous posting - caused also by my colour-disturbance.

I thought the impervious layer is UNDER the rubble and the pervious layer above the rubble. The latter is correct but the impervious layer is under the topsoil and under the rubble there is nothing. I was also mislead by my understanding that a constructed wetland is isolated from the underground by an impervious layer (either clay or polythene). I thought you had somehow reflected this in your design. My misunderstanding makes all of my questions in my last email irrelevant, sorry for wasting your time.

But with the design having NO isolation between rubble and underground, it is accepted that (a major part of) the effluent percolates into the underground because water always flows downwards and the roots of the bananas entering the rubble from top will only soak and eva-transpirate a smaller part of it. Correct? If yes, this may not be a solution in areas where any percolation will be disallowed due to high groundwater or fissured/karstic rock underground. It will be a solution where the underground has a low infiltration rate and the effluent needs to be distributed over a larger area by the rubble layer (like with a leach field).

In areas where percolation into underground is forbidden, we may have to come back to a solution with secondary treatment with a vermi-filter and distributing the such treated effluent to the surface around the bananas using a solar pump (2m gravity flow is too high). You say ‘treated to a high enough level to safely discharge to soil surface’. Do you have test data of the properties of this effluent, i.e. BOD, COD, pathogens, ascaris? This will be necessary to convince ZEMA (our local environmental protection agency) allowing the distribution of the effluent to the surface.

I will have to discuss with our partners whether they can imagine replacing septic tanks with vermi-digesters. I also see the advantages of aerobic digestion, easy reusable output product, possibly longer emptying cycles and safer service chain management.

We are not only discussing the use of vermi-composting for on-site sanitation facilities but also as a solution for large scale treatment of sewage and faecal sludge collected at a central treatment plant. Have you heard of Prof. Dr. Rajiv Sinha who has developed such treatment plants at Griffith University and says having implemented them commercially in India through TRANSPEK? If you haven’t, I can send you a number of research papers which he has given me. I like to have your opinion on his research and commercial application. He also claims ‘his’ treatment eliminates helminths (which is why I contacted him in the first place).


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