Effective sewage sanitation with low CO2 footprint (Duke University in Durham, North Carolina, USA)
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TOPIC: Effective sewage sanitation with low CO2 footprint (Duke University in Durham, North Carolina, USA)

Re: Effective Sewage Sanitation with Low CO2 Footprint (Duke University in Durham, North Carolina, USA) 19 Sep 2013 12:50 #5695

  • dorothee.spuhler
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Thank you Naomi for this write up.

I would like to add one interesting point from the discussion. Bincy (see here for information on her project a self-sustained e-toilet), having the perspective of the product designer, wondered why this toilet has to be elevated and if the group has thought of coming up with a underground structure.
In fact the reason why it is elevated is that they use gravity flow for the whole system and the heat digester and burner has to be flood-protected and accessible. Yu-ling from the University of the Toronto (smoldering toilet) confirmed the same aspect for her toilet.
Indeed, making these toilet flood-proof is yet another challenge!

But Aaron, I have another question for you:
Since you started the field testing, can you say already something on first experiences regarding water content of the sludge and biogas production? How does the lab simulation fit to the real conditions with the 25 people? Is the usage stable? If not, can the system absorb that?

Moreover I was also wondering how you are implementing the us of the sludge from the digester. Do you get temperature sufficiently high to be sure about the inactivation of pathogens? Who is using the sludge for what and what frequency do you empty the reactor (it is batch isn't it)?

And then something completely different: have you already though of an operation system? Who is going to own/construct the toilet and who takes care of the maintenance? Have you also thought about something like a business model as it was presented by Tove? What would be investment costs, life-spam and costs for the users?

Looking forward to hearing back from you!
Best regards
Dorothee
Dorothee Spuhler
WG1 Co-lead
Working with Sustainable Sanitation and Water Management (SSWM) based at at seecon, Switzerland
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Last Edit: 19 Sep 2013 12:50 by dorothee.spuhler.

Re: Effective Sewage Sanitation with Low CO2 Footprint (Duke University in Durham, North Carolina, USA) 15 Jan 2014 20:23 #7005

  • aforbisstokes
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Thank you for the questions Dorothee.

The biogas production has been encouraging, and we have found sufficient biogas production for operating the pasteurization. Quantifying production has proved difficult in the field, however, so I cannot comment at the moment on comparison to lab production.

The reactor operates more like a completely mixed/completely stirred tank reactor in that flow in equals flow out (with the exception that we do not have mixing) - influent volume displaces the same volume of digester slurry into the heating system. Effluent is currently collected for lab testing.

Operation for the system is still being developed. Currently our local collaborators regularly check on operation. For the sites we are working with in Kenya, plots are owned and supervised by a landlord. We imagine that person would ultimately be the owner and the one responsible for the system. The systems in Kenya were built by a local company has the knowledge and abilities to construct future systems. The most likely business model set up would involve using the effluent as a fertilizer. One of the plot owners has already expressed interest in doing so. The excess biogas (what is not needed to power the pasteurization) would be more difficult to sell as a product, but represents a better option for cost savings by reducing the need to purchase other fuels.

Thanks!
Aaron
Aaron Forbis-Stokes
Duke University - Graduate Student
Environmental Engineering
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Re: Effective Sewage Sanitation with Low CO2 Footprint (Duke University in Durham, North Carolina, USA) 10 May 2014 15:15 #8557

  • AquaVerde
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Dear Aaron,

I am unfamiliar with the abbreviation "CHP." What does that stand for?


sorry for being very late: en.wikipedia.org/wiki/Cogeneration:

Cogeneration or combined heat and power (CHP) is the use of a heat engine[1] or power station to simultaneously generate electricity and useful heat.

All the Best
Detlef
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Sanitation-Solutions without external energy
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