Household Ecosan toilets (UDDTs) in rural Ghana - and discussions about reuse opportunities and risks

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  • paresh
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  • Budding WASH researcher, especially interested in governance, public policy, finance, politics and social justice. Architect, Urban & Regional planner by training, Ex. C-WAS, India. I am a patient person :)
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Re: Household Ecosan toilets (UDDTs) in rural Ghana - and discussions about reuse opportunities and risks

Dear Heiner,
I agree that we need to consider life cycle costs of interventions and changes in our consumption habits. Also agree that the costs need to be calculated on multiple dimensions - financial, water footprint, carbon footprint, etc. and it makes more sense to concentrate nutrients in urine if it needs to be transported over distance.

I was sure you had already seen Scott's work but wanted to build a link to that thread for other members and for future reference.

regards
paresh
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  • Tore
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  • worked in sanitation for most of my life. taught plumbing. have plumbing and builders license, certified inspector in all facets of construction, PhD in public administration & have taught construction management in university, traveled numerous countries, Interest UDDT and sanitation & clean water
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Re: Household Ecosan toilets (UDDTs) in rural Ghana - and discussions about reuse opportunities and risks

The acaris eggs are always the last to die and you are restricted to time and temperature.  Elevating either will help destroy the eggs.  In most cases it is easier to increase the temperature to quickly kill the eggs and use the product.  Since you still have viable eggs after 6 months of storage and the product is totally dry then the volume is not very large.  I would suggest making a box with a glass window facing south.  In the past I have constructed passive water heaters which was simply and insulated box with a glass window to the south and a water storage tank inside.  On a sunny day I would achieve air temperatures of between 250 and 300 degrees F. which is more than adequate to kill any remaining acaris.  You would not need more than a single sunny day to kill any remaining pathogens and make the dried feces usable for agriculture.
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  • hajo
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Re: Household Ecosan toilets (UDDTs) in rural Ghana - and discussions about reuse opportunities and risks

Dear all,

You would not need more than a single sunny day to kill any remaining pathogens and make the dried feces usable for agriculture.

This remark by Tore in his above posting, motivates me to raise a proposal again, which had been shortly discussed between Chris Canady and me in this thread earlier (page 1).

Chris recommended that in UDDTs which are used by unknown numbers of users (or numbers beyond the design capacity), the vault could be replaced by sacks in containers. When a sack is full, it can be taken off the container and be replaced with an empty one, while the full sack can be stored for treatment.

I had recommended to place the sack in the full sun of a sunny day (we talk of a project on the Ghana coast!), turning it around so all sides get 2 hours bright sunshine and are heated up to 500C killing all pathogens within 2 hours (each side).

Chris warned that the UV would destroy the sacks. I felt that it was a misunderstanding in such that he assumed the exposure to sun would go on for longer time. I assumed it would be a day's job following the same information as Tore (above) that few hours of high temperature is enough to kill ascaris (and all other pathogens).

Of course this has to be investigated a bit: how thick can be sack, so that also the core is heated to 500C (chef's thermometer!)? Protection against rain and moisture from ground? How long will it take to reach the temperature? What additional assistance can we give to reach sufficient temperature (sun reflecting material under, heat-absorbing material above the sack)? But these are all aspects which do not require a university laboratory, but just some innovative ideas and can be done on site by DBG.

ciao
Hajo
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  • Linda2019
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  • Dr Linda East is an Honorary Associate Professor in Health Sciences (Nottingham University, UK) and a Trustee of Dream Big Ghana Foundation (UK).
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Re: Household Ecosan toilets (UDDTs) in rural Ghana - and discussions about reuse opportunities and risks

To all who have contributed, thank you so much.  Tore and Hajo, this latest advice is very timely as we have a meeting this afternoon to plan some experiments!All best,Linda
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  • Tore
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Re: Household Ecosan toilets (UDDTs) in rural Ghana - and discussions about reuse opportunities and risks

If the feces have been in storage for 6 months they have dried and most of the pathogens have died.  As stated earlier people do not want to handle human waste.  This is especially true with feces.  Once the feces has dried it no longer looks or smells like feces and it is easier to convince the local population that it has changed and is now a soil conditioner/fertilizer.  If there is a concern for acaris eggs then putting this soil  conditioner in a box with a window for a day is easy.  Since it is dry it is easier to heat and achieve a temperature above 160F so all is dead.  I would recommend wearing a mask and gloves since the material is a dry ash that has a tendency to fly everywhere.  Remember it no longer looks, smells, or acts as feces so rename it to a more local acceptable term.

Linda, If you are doing an experiment I would recommend building a simple box with a glass window and take temperatures.  Also put in some 6 month old soil conditioner and check the temperature at various depths.  The thinner the depth the more certain you can be that the temperature has been reached.  I have a chart in my book that shows time/temperature relationship to achieve total death though the acaris is especially hard to kill.

Remember: Don't let the perfect become the enemy of the good!
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