Windmill-driven ATADS

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  • sjoerdnienhuys
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  • Technical advisor on low-cost sanitation, worked for Aga Khan in the Himalayas, PUM in Asia,/Afica and Latin America, SNV in Nepal, DGIS in Latin America UNhabitat in Africa, and Waste /Gouda in India on ECO sanitation and biogas
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Re: Windmill-driven ATADS

@marijn. I think that an important priority is to reduce any methane emissions from sanitation systems through the integration of biogas reactors with sewage. At city level the UASB is being used but other city sewerage make the sludge dangerous. Therefore direct toilet based biogas reactor is preferred.

In Nepal the biogas project attaches the house pourflush toilets to their small farm based biogas reactor, but urban development for cluster houses is not yet done. The few cattle produce much more dung of good quality than the household members. When we did the first methane leakage measurements on these small rural biogas reactors (now over 250.000 constructed) it appeared that there was substantial leakage. See sketch. This leakage was not resolved but the project managed to get good carbon credits anyhow, co-financing the management costs.

In developing toilet systems you can forget the carbon credits because you need massive results to make it economic or recover the investments. But when you have large numbers it is a worthwhile financial contribution. If some countries continue to frustrate the Kyoto protocol that financing may not be sustainable.

@Jim. I figure that blowing air through toilet and animal faecs with methane gas produces an explosive mixture. It will be dangerous to burn this mixture off. When not done it contribute strongly to global heating. That is why it is important to quantify the methane production of all sanitation units and design systems that capture the biogas (without air).
Sjoerd from The Netherlands.
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  • Marijn Zandee
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Re: Windmill-driven ATADS

Dear Jim,

I was a little surprised when you wrote " Surely no one wants to make methane as an integral part of a decentralized system. It is just too dangerous".

I assume that you don't consider bio-gas technology as too dangerous to use? If so I would be interested in your reasoning.

@ Sjoerd, I agree it would be interesting to look at sustainable sanitation from a global warming perspective as well. As long as we don't tie it up to carbon credits or similar. (I know we disagree there) By the way, here in Nepal we have some bio-gas attached UD toilets, seems to work fine as-long as you have a couple of animals to create enough feed-stock (or connect a lot more toilets).

Kind regards

Marijn Zandee
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Re: Windmill-driven ATADS

One more thing. On our next battery of runs, I will monitor lower explosion limits and try to analyze for CO2. This may be months from now. Regards, Jim
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  • sjoerdnienhuys
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Re: Windmill-driven ATADS

All sanitation systems have advantages and disadvantages, wheres we try to reduce these disadvantages. Sanitation systems however, produce methane somewhere along the line, where dry or wet systems.
In relation to sanitation you can possibly define three levels; Private, Public and Global.

Private is appealing to the individual user and includes personal and family health, personal expenses, comfort, recurrent cost, etc.

Public includes the cost of delivering water, the entire sewerage system and the sewage cleaning activity or other communal services that are not individual. These expenses however, are somehow paid for by the individuals through specific tariffs or general taxes. General public health related to no sanitation or better sanitation also falls in this category. When we look at sanitation systems we see that more water results in more sewerage, through which the cleaning also becomes more costly.

Global is related to the impact of human sanitation on the environment. One of the most important aspects is the cleaning of the sewage so that it does not affect negatively all our surface water, irrigation, fish or algae development, etc. The emissions of CO2 and methane gas are part of the global and environmental issues. Human excreta produces methane gas when aerated or in biogas reactors. While the methane gas is captured in biogas reactors and can be burned off to CO2, with other sanitation systems this methane is emitted into the atmosphere. It is 21 time more insulating as a greenhouse gas than CO2. Human faeces composted or aerated including from septic tanks and ATAD is there fore a major contributor to global warming. Global warming in turn leads to permanent melting of more polar ice, larger and more frequent tornadoes, expansion of deserts and more droughts in some regions with resulting food shortages, and excess of rain worldwide causing floods, and not the least of all the rising of sea level with two storeys, requiring a billion people to move to higher land and loss of agricultural land. The book/film "An Inconvenient Truth" gives a short account of the issue.

It is my opinion therefore that all sanitation systems need to be assessed on CO2 and more import on methane emissions (NH4) into the atmosphere and rated. This can be an interesting task for SuSanA. Most likely the least damaging systems are the UDT models in combination with a biogas reactor, from which the biogas is used for cooking.
Sjoerd from The Netherlands.
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Re: Windmill-driven ATADS

Here is the photo of our system, capable of handling 15-20 people. No power, no water needs, no chemicals, low maintenance, cheap (BMGF Grant Requirements) Regards, JWB
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Re: Windmill-driven ATADS

Hi.

We've just finished our 6 month Windmill-ATAD system and can add to the discussion of methane. Surely no one wants to make methane as an integral part of a decentralized system. It is just too dangerous.

Our continuous ORP data shows over a span of wind speeds and an underpowered windmill, reactor liquid never enters the methanogenisis range and except for a brief time span where we "wired" the system to be in the high aerobic range, It was steady in the denitrification range. We had no observable odors. Regards, Jim
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Re: Windmill-driven ATADS

@Christoph, Thanks, I have clarified the text.
The content of the UDDT you can dump in a biogas reactor for sanitization and gas production. The UDT, being a wet system (even anal wash is possible), can be directly over a biogas reactor. Since the ATAD is also a wet processing system, it is likely that methane gas with bad odour is generated. This is actually the case. Given the importance and the danger of global warming, one need to ask how methane gas is avoided, and if the ATAD is a suitable system in this context.
Sjoerd from The Netherlands.
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  • christoph
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Re: Windmill-driven ATADS

Dear Sjoerd,
it seems you got something wrong. It is not Automatic Thermophilic Anearobic Digestion it is autothermal thermophilic AEROBIC digestion.
As well as UDDT are AEROBIC not anaerobic systems. That is a very crucial point. I really don´t understand your posts (some in the Forum) which are pointing to anaerobic UDDT..if a UDDT is anaerobic soemthing has gone very wrong.

Christoph
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Re: Windmill-driven ATADS

A centrally located Autothermal Thermophilic Aerobic Digestion (ATAD) system is very useful and probably essential to receive the content of any toilet system including UDDTs in an urban environment, provided the UDDTs can be emptied regularly. Link with the discussions on UDDT would be fruitfull.

To my understanding, the ATAD digester e.g. www.dayton-knight.com uses water and air to process the content at high temperatures and sanitizes the content.
However, the capture and burning off of the methane gas is very important. This however, is hardy possible in an aerated system. The effect is that methane gas escapes into the atmosphere, being 21 time more insulating than the CO2.

The windmill ATAD needs some essential technologies to consider.
1. More wind energy is obtained at higher level above the ground. For detailed information on windmills see website of: www.RETscreen.net
2. Other wing or propellor designs will generate more electricity for heating with the same amount of wind. Heating will be required in low temperature environments. The low-speed rotor in the picture is suitable for mechanical transmission such as a water and air pump, but less energy efficient for electric power.
3. Because of the moving parts in the windmill, such design requires high maintenance; this however is a serious problem in many (developing) countries.
4. Thermal insulation of the (underground) tank or reservoir is important in the colder areas to obtain thermophillic processing. This becomes more important in countries with a cooler season and essential in countries with a winter such as South Africa, and higher altitude zones world wide. The process time should be short, otherwise the retention time needs to be substantially increased.
5. Stirring of the content of the ATAD reactor is important not only to mix the air, because people throw all types of waste into the toilet such as non-digestable paper, condoms, sanitary napkins and even used seringes. These plastics and solids need to be removed occasionally.

The question raised is if the production of methane gas is avoided in an ATAD, or how it can be avoided?
Sjoerd from The Netherlands.
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Re: Windmill-driven ATADS

Hi.
We have completed the first 6 month run of the system and are just now analyzing data.
I will probably have a report to BMGF soon and will submit a paper thereafter. Regards, Jim
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Re: Testing an ATAD System

I'm Jim Blackburn and I'm interested in a windpowered ATAD. We have one, but in the six months we ran, only an industrial waste was available. I'm trying to find a material of significant TS %6-8? and a BOD/COD ratio of the feed at or above .5 (10 gal day). the volume needs drive us to sources from waste water treatment. Any suggestions. Thanks Jim


(note by moderator: I have moved this posting to the earlier existing thread on this topic. EvM)
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Re: Windmill-Driven ATAD (Autothermal, Thermophilic Aerobic Digester for increased pathogen removal)

Hi.

We’ve just finished all the packing and will be picked up on Monday. Our team is looking at Wind-mill driven Autothermal Aerobic Digesters at a very small scale. We’ve run this system at scale for about 5 months, and we think it may work for people who live in places of moderate or higher wind. It’s thermal mass buffers changes in the environment. We’ll bring the system itself and show how it works as well as bringing a model that shows how the ATAD might fit into an enclosure. We are also very optimistic that water produced from the system will be so low in pathogens that it could, with a hand pump, allow the benefits of a flush toilet with treated water without the problems. The only problem (but a big one) was that we were unable to get the reactor above 34 degrees C when it requires 55-65 degrees C to do the disinfection. We believe that this is due to the inhibition and toxicity of the mostly-industrial waste sludge we had to work with.

We hope we can continue with an all biological WWTP return sludge which will simulate the final all excreta material and very high reductions in pathogens–the goal of the Foundation.

I am coming: to meet all of my colleagues, to learn from their experiences, to maybe gain some information of issues we’ll still have, after proving the disinfection potential, to introduce two of my co-workers and to have some fun.

Regards, Jim

++++++++
We have started a new thread, it was getting a bit long. The new thread starts here:
forum.susana.org/forum/categories/105-hi...l-report-and-results
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