Solar treatment of feces? - to treat feces with solar energy in order to kill the pathogens in the feces quickly

  • Kevinkuhn
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Re: Solar treatment of feces?

Hi Harry,

interesting idea. Thanks for the input.

So what I see is that, the pad is quite small. So I guess the feces chamber has to be designed smaller as well. Do you have any idea about the ratio from the pad to the volume it can heat up? I would also like to know what the lifetime of such a pad might be? I would like to set it and forget for min 10-20 years.

Best
Kevin

Non-Water Sanitation e.V.
www.nonwatersanitation.de

EcoToiletten - Rental for composting toilets for festivals and construction sites in Berlin, Germany
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  • RaVikas
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Re: Solar treatment of feces?

Dear SuSanA members,
Greetings,
My solar therm worm toilet, is functional for more than 18 months till date here in India
Installed for general public this toilet averages between 30~40 users daily along with 45-50 urinal users.
It generates between 65-90 degree C from regular temperatures ranging between 25-42 degrees C to sterilize pathogens
UDDT is customized to anal washing for India.
Working with negligible maintenance has no moving parts,needs no electricity, no water to flush, no odor, no flies or vectors and has extended holding capacity.
Thank you
Ravi Senji
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  • Ashok
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Re: Solar treatment of feces?

Dear Ravi Senji,
I would like details of your solar therm worm system.
My email address is This email address is being protected from spambots. You need JavaScript enabled to view it..
Ashok Jain
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  • SeptienS
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Re: Solar treatment of feces?

Hello again,

The design of Harry is interesting, but I am not sure if it would feasible for a large volume of feces. It will be necessary to perform a heat balance to determine the amount of heat required to maintain the faces at the desired temperature for its disinfection. With this information, it will be possible to determine the electrical power required for heating and thus the area of solar panels. Once this study will be performed, we will know if this possibility is feasible with the available resources.

I have an alternative suggestion. We can use a water solar heater and make circulate the hot water inside the chamber containing the faeces. We can expect that this system would have a higher efficiency than the photo-voltaic one. Indeed, a solar water heater has an efficiency to convert the solar energy into heat between 50 to 70%, whereas a solar panel exhibits an efficiency to convert the solar energy into electricity about 20% . Moreover, in the photo-voltaic system, the electricity has to be converted into heat, which represents one more step in the conversion of solar energy into heat, so an extra stage of loss of efficiency. Nevertheless, a full technical-economical study should be performed in order to determine if the gain of efficiency in the thermal system is worthy by considering the capital and running costs of both systems.

Another alternative is to add a transparent window in the chamber in order to allow solar radiation penetration, as suggested by Tore. the orientation of the window should be south in the north hemisphere, or north in the south hemisphere. You could also include mirrors and reflectors aside to increase the amount of heat received in the faeces storage chamber.

To maximize the performance of pasteurization, you could combine the transparent window design and heating by water heater or photo-voltaic cells.

I hope that my answer was helpful. I am available for further discussions!

Kindly,
Santiago

Dr. Santiago Septien Stringel
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  • jscheerer
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Re: Solar treatment of feces?

Dear Kevin,

I just read your post regarding the possibility of killing pathogens in faeces generated in a UDDT. In that context I would like to draw your attention to Sani Solar, designed as a dry sanitation system for rural areas with hot climate ( 3psanitation.de/the-product-sani-solar/?lang=en ).

Sani Solar consist of a functional unit based on solar radiation and convectional air- flow, which can be combined with any kind of cabin structure.

It would be good to know more details about your project in order to evaluate the feasibility of using this technology.

Best regards,

Jochen Scheerer

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  • hajo
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Re: Solar treatment of feces?

Hello Jochen,

Thanks for drawing attention to your technology which seems so far only be promoted in Asia and Southern America. In Africa I haven't heard of you. Some few remarks and questions:
  1. I assume that your users prefer using toilet paper for anal cleansing. What about 'washers', they could possibly over-strain the drying capacity in the containers?
  2. Don't you have problems with men standing and peeing into the faeces compartment? We therefore use recommending the installation of an urinal.
  3. How about the emptying? Users get used doing it by themselves or would rather prefer an emptying service?
  4. How many units have you installed so far and what is the ex-factory price (let's say for a full container)?
  5. Do you face problems of vandalism, especially with the urine vaporiser sitting on the ground?
  6. Do you have a special reason why the system is promoted for rural areas? Is it not also applicable in peri-urban areas of cities where sewers and water supply are lacking?
  7. You link your posting to the question about pathogen removal in UDDT but you do not make any statement regarding pathogen removal in the SaniSolar!?

Looking forward to your responses,
ciao
Hajo

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
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  • jscheerer
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Re: Solar treatment of feces?

Dear Hajo,
Thanks for your interest in our technology.
Indeed, we have started to work with Sani Solar in Brazil, Chile and Mexico. However, we have a pilot site operating at Guinea Bissau since more than one year and three more units just had arrived in Africa, two of them in South Africa and one in Kenya.
In the following I will try to answer your questions:

1. The system is based on a drying process driven by the sun and climatic conditions in warm and arid regions. Any extra water introduce into the system will interfere with this drying process and should be avoided. For that reason the system is not suitable for “washers’” in its current configuration.

2. As in any UDDT, men standing (and not aiming well) would spoil the separation process and therefore this is not a desired practise. However, in all the pilots we had no significant problem with this issue after explaining the concept to the users and make them understand the benefits of changing habits. We experimented with a urinal, but it turned out to be a source of odours, something we wanted to avoid in any case.

3. The original approach of our system was to provide a sanitation solution for remote rural areas suffering from water scarcity and lack of all kind of infrastructure or service. In those terms the user himself can perform emptying in a hygienic safe way without the need of special equipment or training. According to our experience emptying was generally accepted, however there where differences related to gender, culture and socioeconomic status. In case an emptying service can be provided surely it would be preferred, however depending on the related cost.


4. So far we have installed 16 units in different parts of the world (Brazil, Chile, Mexico, Guinea Bissau, Singapore, Spain). The current Ex works price from Germany is 2.550 €/ complete unit (with cabin structure) and 1.500 €/ functional unit. In a 40 “ Sea Container we could ship 16 complete units or 32 functional units.
Our future concept for Sani Solar is aiming for local production in order to reduce cost according to the local market.
It is important to consider that we are talking about a system that needs neither external service nor commodities.


5. So far we did not have any problem with vandalism. For sure that has to do with the fact that the systems are operating in a rural environment with good relations between the neighbours.

6. The focus on rural areas comes from the beginning of the Sani Solar project, which was initiated in the context of a governmental project in rural Northeast of Brazil (“Agua para Todos”). Also the system is designed for autonomous operation in remote areas, it could be used in urban or peri-urban areas as well. In any case different criteria, as for instance the vandalism aspect, or possible shading by higher buildings, have to be considered.

I hope that I could answer your questions in an adequate way and looking forward to receiving you comments/considerations.

By the way, I saw you are located in Lusaka! We are currently working with Raise a Smile and Terra Nova Children's home on a interesting sanitation project in the Luapula province in Zambia.


Best,

Jochen Scheerer

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  • hajo
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Re: Solar treatment of feces?

Hello Jochen,

thank you for your comprehensive response. I see the advantage of the SaniSolar compared to a standard UDDT in the 'turntable' which probably speeds up the drying process and in the immediate drying of the urine in the evaporator.

While it has similar limitations as the UDDT (not for washers, wrong use by men) and some additional (vandalising of the evaporator).

Is it possible to get a bit more technical details about the evaporator? How does it function? How is the 'fresh' incoming urine separated from the 'old' already dried urine? What is its capacity? What is the end product? What are the properties of the end product? Did you do any chemical analysis what is the fertiliser value of the dried urine?

What is the difference in delivery between the complete unit and the functional unit?

You mention considering local production. You may get in contact with ENVIROSAN/Durban or KENTAINERS/Kampala/Nairobi who both produce sanitation components in the region from PVC/PE as a possible partner.

ciao
Hajo

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
Albert Einstein
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  • jscheerer
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Re: Solar treatment of feces?

Hello Hajo,

Thank you for your comments and information’s regarding potential partners for local production.

Please find my answers to your questions below:

Function of urine treatment:
After usage the urine is conducted into the urine treatment unit outside the cabin where it accumulates on the steel plate (see image 1 attached).
During the day, the accumulated urine is heated up (depending on the climatic conditions up to 80°C) and stabilized. Further more the water evaporates.
For the harvesting, please have a look at our homepage under the following link:

3psanitation.de/videos/?lang=en
The video is called collection and disposal.

Eventual overflow is conducted into a small reservoir (10 – 15 l) in order to facilitate eventual emptying (see image 2 attached).
In the recommended climatic conditions, the evaporation capacity is approx. 3L/ d.

A sample of the dried residue has the following characteristics:
Dry matter: 79,35 %
Total N: 181.000 mg/ l
Nitrate: 55.740 mg/l
Total P: 20.250 mg/l



Functional unit:

We call the functional unit, the core part of the system, which can be installed in combination with any kind of cabin.
Please se pdf attached.



Best,

Jochen Scheerer
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  • hajo
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Re: Solar treatment of feces?

Hello Jochen,

thanks again for the again open and detailed information! I didn't always find commercial suppliers so open with information on the forum.

Since you have a 'chemical heavy-weight' behind you, you can easily provide figures how the dried urine-fertiliser compares with industrial NPK fertiliser. I could possibly find out by myself but for you it is much easier... ;)

We have not yet talked of the pathogen removal in the SaniSolar. Do you have any information regarding this matter? In 'standard' UDDT sometimes ashes are added lowering the pH and killing pathogens... except for helminth eggs which can only be killed by temperatures > 700C. This aspect is of relevance if the dried faeces shall be used in agriculture.

Just a quick observation: these small washers and wing-nuts holding the windows will easily get lost, and cannot easily be replaced by a local household.

ciao
Hajo

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
Albert Einstein
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  • JKMakowka
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Re: Solar treatment of feces?

hajo wrote: Just a quick observation: these small washers and wing-nuts holding the windows will easily get lost, and cannot easily be replaced by a local household.


Yes some sort of durable clip-on solution would be much more practical.

In general: have you thought about / experimented with a more simple set of plastic moulds that would allow stackable parts for easier distribution?

Microbiologist & emergency WASH specialist
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  • hajo
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Re: Solar treatment of feces?

hello Jochen,

In the recommended climatic conditions, the evaporation capacity is approx. 3L/ d.


I forgot in my last posting to ask about the capacity of the toilet. I read somewhere it is meant for 5-6 people, but they produce between 5 to 6 L of urine in a day. Thus the evaporator cannot handle that quantity and the 'balance' reservoir will always fill up, or?

ciao
Hajo

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
Albert Einstein
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