I developed an open source composting / vermicomposting toilet design based on an ordinary flush toilet

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  • WendyHoward
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  • Biologist/ecologist/educator running a permaculture centre in Central Portugal. Came across vermicomposting/vermifiltration in waste management in 2013 and developed an open-source DIY system based on one pioneered by Anna Edey in the 1990s and using conventional flush toilets. Passionate about restoring life and health to the planet's ecosystems.
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Re: History of vermifilter toilet and wikipedia article

You might go visit Anna Edey's system. I lived nearby on the mainland and visited there. The system folks usually talk about was dismantled years ago. What she emphasizes is using a shallow rootzone distribution system for leachate. The system you see in her book from the 1990s was no longer there. She had a simple urine-div system with bucket in place for her own use.


That';s not the case according to Anna Edey herself, who wrote on my site in 2015 "I’ve now had mine going constantly for more than 20 years without any odors, flies, clogging, freeze-up or other problems – it is reducing nitrogen pollution into the groundwater by better than 90%."

Or according to this post , written a year later.

Or are you talking purely about the 'greenfilter' element of her system? In which case, a shallow root zone distribution system is exactly what's being used in my adaptation of her system.

What you say about the tank needing actively aerated, emptied and the timescales involved does not match with my experience at all. The organic material in the tank is both substrate and feedstock for the ecosystem, so it's consumed. Far from needing emptied, the tank needs to be regularly topped up with fresh organic material. Active aeration is not necessary.

My system has been going for 7 years now and has never needed emptying. It handles the waste of between 1 and 6 people on a regular basis, depending on the number of people staying onsite at any time, and occasional short-term peaks of up to 20. The ecosystem survived the wildfires which destroyed the house it was attached to and half burnt the tank. All we had to do was transfer the contents to a fresh tank (not particularly difficult since a hatch is cut into the top of the tank to allow easy access for organic material additions, monitoring and maintenance).

A number of others locally have adopted the system so we are building up a body of experience. We are finding that it's important to have a good mix of carbon sources, including some relatively chunky wood waste. The latter keeps the substrate well aerated as well as providing a matrix for the microbiology to inhabit. Where people have relied too heavily on dried leaves for their organic material additions, occasional problems have been encountered with the water getting hung up in the tank fairly high up. The leaves, once wet, stick together and form a mat which acts like a membrane, preventing easy flow of water through the system. In most cases, the problem is easily solved by perforating and mixing the upper layer, adding some fresh dry organic material, and letting the system rest for a few days while the worms deal with the backlog of waste.

It's important to emphasise that this is a living system which requires monitoring, care and maintenance to ensure optimum conditions are maintained. However the maintenance is far less than for most dry systems. 7 years on I remain very happy with it and am about to build 2 more to cope with increased visitor numbers to the site.
Quinta do Vale - Permaculturing in Portugal
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www.vermicompostingtoilets.net/
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  • Ecowaters
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Re: History of vermifilter toilet and wikipedia article

I think I was there in 2007 or 2008. I'll confirm later. Her above-ground aerated system was dismantled.
She had a below-ground tank with shallow leachate system. These are allowed in Massachusetts, as they are a variation of several systems. (However, since she had a legal septic system in place, she's mostly allowed to do what she wants.) She has worms in hers. Like many septic tanks that aren't super-loaded, it likely hasn't been pumped out in a long while.
There were several changes in her house, as Martha's Vineyard residents often rent out all or parts of their homes thanks to the lucrative rental market. She explained to us why and how she changed her system, which changed her wastewater systems.

A below-ground tank with worms in it is not especially new. The design she has is related to other systems in place in her state due to onsite wastewater regulations that were made stricter in 1995. She is guessing at the nitrogen reduction percentage, however, I'm sure it is much more sound than a conventional system. This is a big issue in coastal Massachusetts.

Again, not easy to empty those big translucent tanks. I think what you're saying is you could have it pumped out if you needed to empty it. It would be difficult to empty any solids.

None of this is to say that these systems don't work. There are many variations of these out there. Some have no more evidence of worms but still work very well if they are aerated and/or vented---because that contributes to success more than worms.
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  • WendyHoward
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  • Biologist/ecologist/educator running a permaculture centre in Central Portugal. Came across vermicomposting/vermifiltration in waste management in 2013 and developed an open-source DIY system based on one pioneered by Anna Edey in the 1990s and using conventional flush toilets. Passionate about restoring life and health to the planet's ecosystems.
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Re: History of vermifilter toilet and wikipedia article

Again, not easy to empty those big translucent tanks. I think what you're saying is you could have it pumped out if you needed to empty it. It would be difficult to empty any solids.


Pumped?! You can't pump solid material! This is an aerobic composting process which consumes material rather than needing to be emptied. At least over the 7 years I've had it running. I see no signs to indicate that process will alter its fundamental dynamics anytime soon. Should I want to use some of the compost, it's easy enough to dig out.
Quinta do Vale - Permaculturing in Portugal
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www.vermicompostingtoilets.net/
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  • Ecowaters
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Re: History of vermifilter toilet and wikipedia article

Wendy, I wrote a book about composting toilets.
That's my point: They are hard to empty. And some folks are saying that's not an issue. Then I find out it is an issue.
Those cubes are also used by people creating composting toilets. Two years later, you find they have abandoned that design because they are hard to empty without cutting them up and risking leakage after that.


Many (not all!) septic tanks go years before they are pumped out.
So much depends on the temperature, volume, throughput, design (the 2-chamber and 3-chamber designs work better), and leachate system.
Septage is sludgey but with enough moisture, a pump truck can remove it.
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  • goeco
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Re: History of vermifilter toilet and wikipedia article

The advantage with the 1 cubic metre vault is that the volume accommodates seasonal variations in decomposition efficiency (e.g. winter). However, required vault size is directly related to
  1. number of users, and
  2. required length of time before the contents need emptying.
A larger vault is required for more users, or if you don't want to empty it for a long time.

The cold hard fact is that there WILL be an accumulation of carbonaeceous material, called humus. Anyone who has composted anything knows that the bulk reduces significantly but does not disappear. To explain, lets use the concept of half-life. A unit of carbon reduces by half over a unit of time. Over another unit of time it reduces by half again. Then over another unit of time it reduces by half again. It never disappears. Then, because each day you are adding more carbon, that carbon does the same. It is fantasy so imagine that the carbon all ends up oxidising to CO2, even under fully aerobic conditions. Even if you diligently turned a pile of turds regularly for rapid decomposition, whatever oxidising organisms you use, whether worms or micro-organisms, you end up with humus. Humus is stable carbon and does not decompose further in human time frames, it is the stable soil fraction that originates from plant carbon, as a result of photosynthesis. There are other factors that influence the time it takes for humus to build up... e.g. Washers or wipers? Worms digest toilet paper much more slowly than poo and more humus is produced per person. Also, suspended solids may be high in wastewater exiting the primary vermidigester. Claiming that the solids never build up only suggests to me that your soakage fields will have a limited life due to siltation.

Of course, vermifiltration does a remarkable job of decomposing the solids if the system is set up correctly. Compare this with pits, an extraordinarily primitive method for disposing of fecal matter, where solids usually do not reduce until removed from the pit. Quite ridiculous, yet still practiced in the 21st century! Primary vermifilters (e.g. vermifilter toilets) are also a big improvement on septic tanks (humus instead of sludge) and should be promoted more widely. What people often don't realise is that, like septic tanks, you can also put greywater and blackwater though them, provided the soakage fields are appropriate.

Next, the key to setting up the system correctly is that you need a flush toilet feeding into it. It might even be micro-flush, but this is essential to dilute the urine. A  250 gallon IBC tank "composting toilet" at events would likely not be a flush system, because for flush you also need soakage fields, which tend to only be set up for a permanent system.

Wendy's system clearly works but is it optimised? The idea with the one cubic meter IBC tank is great for temporary setups where cost must be low... but those cheap tanks tend to become brittle after a while. Why it works is not because of the 1m3 capacity, but the 1m2 surface area. In times where biological activity is low (e.g. winter), solids will build up on the surface. The digester must have sufficient surface area for those contents to spread out unimpeded... a 1 m2 surface area is sufficient for most households. Where I have some reservations in terms of overall efficiency is that ventilation of the substrate is limited in a tank with ventilation only at the top - and not at the bottom of the substrate where oxygen is needed the most. A well designed system allows for ventilation around and underneath the substrate, which I have shown how to achieve in other posts. However, I accept that a deep substrate and lots of coarse material may provide sufficient ventilation through the top layer of media for a domestic system. But I will say that a GOOD system requires NO monitoring, care or maintenance beyond removing the humus every x years.

I will also be clear that a well designed system must provide twin digesters, because eventually a single digester will fill up, which might take five years, ten years or even twenty years depending on capacity and average number of users. The fresh stuff will be on top and nobody likes cleaning that out from a hatch. In contrast, removing humus from the rested side is a pleasure. There must also be a means for the worms to migrate from one digester to the other.

Next, the "greenfield" or "leachate distribution system" is essential for a vermifilter toilet because it flushes... and therefore generates a quantity of primary-treated wastewater. This is not different from wastewater effluent from a septic tank. The simple rule of thumb is to design and construct soakage fields so that the water is dispersed (rather than concentrated) so it does not enter water tables. Lots of novel ideas abound, but in my view to really take advantage of the nutrient rich water discharged form the primary vermidigester, a secondary vermifilter should be installed so that surface irrigation can be used. This means you can take the water directly to the plants you want to feed using drippers, with suspended solids removed, a low BOD and low pathogen levels.
Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
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  • WendyHoward
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  • Biologist/ecologist/educator running a permaculture centre in Central Portugal. Came across vermicomposting/vermifiltration in waste management in 2013 and developed an open-source DIY system based on one pioneered by Anna Edey in the 1990s and using conventional flush toilets. Passionate about restoring life and health to the planet's ecosystems.
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Re: History of vermifilter toilet and wikipedia article

Humus is stable carbon and does not decompose further in human time frames, it is the stable soil fraction that originates from plant carbon, as a result of photosynthesis. There are other factors that influence the time it takes for humus to build up... e.g. Washers or wipers? Worms digest toilet paper much more slowly than poo and more humus is produced per person. Also, suspended solids may be high in wastewater exiting the primary vermidigester. Claiming that the solids never build up only suggests to me that your soakage fields will have a limited life due to siltation.


For sure the contents of the tank will convert to humus over a period of time, but for as long as the losses to the system (CO₂ + wash out of the finer fraction of vermicompost) are close to the final accumulation rate, then build-up will be extremely slow. Possibly why Anna Edey claims her system never needed emptying in 20 years?

There is no detectable siltation in the soakage field because you also have the same vermicomposting ecosystem in that which ensures adequate movement and aeration of layers. There can be build-up of silt in perforated distribution pipes if the diameters of both pipes and perforations are too small.

Wendy's system clearly works but is it optimised?


No! That's the whole point of the open source community that exists around it. Currently I'm experimenting with a vertical perforated pipe for improved drainage/aeration.

The whole point in developing the system was to have a low-cost DIY open source solution for ecological waste management that's rooted in a real-world situation and is a bit more user-friendly than dry composting systems. Many people are not prepared to give up their flush toilets. Many people couldn't even dream of affording any of the proprietary systems I've seen. Most cost tens of thousands. And with ever-growing wealth inequality in our societies, I think it's important to have an accessible solution.

In rural Portugal, many people rely on ancient septic tanks. Most are DIY installations. Most don't work properly and in this mountainous region, there's no possibility of effective leach fields as the slopes are too steep and the soils are too thin. Consequently all the surface waters carry a background level of coliform pollution. My aim was to devise a system which would be an improvement on these septic tanks and which local people could afford to install.

The trade-off with low cost DIY is that you exchange your time for the up-front cost of a maintenance-free proprietary system. You acknowledge that the system is still experimental, and you join and contribute to the community working on optimising it.

Lots of novel ideas abound, but in my view to really take advantage of the nutrient rich water discharged form the primary vermidigester, a secondary vermifilter should be installed so that surface irrigation can be used. This means you can take the water directly to the plants you want to feed using drippers, with suspended solids removed, a low BOD and low pathogen levels.


That's exactly what Anna Edey's system (and hence mine also) features. However, in my experience, the water exiting the primary system is not particularly nutrient rich. Certainly not in its early years of operation. It may change once the entire tank contains humus but after 7 years, I'm not there yet. I deliberately planted a lemon tree as an indicator species as they are demanding feeders. The lemon does not thrive on the water leaving the tank. There's not enough nutrient in it. I have to supplement with compost additions.
Quinta do Vale - Permaculturing in Portugal
Facebook - www.facebook.com/QtadoVale/
Websites - www.permaculturinginportugal.net/
www.vermicompostingtoilets.net/
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  • KaiMikkel
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Re: Which composting toilet to choose - recommendations, please?

"A pathogen which can produce a fatal outcome in one context can be benign in another."

OK, so how's this for context? Water from your so-called sanitation system which is contaminated with Shigella bacillus, Vibrio cholerae serogroup O1 and e.Coli O157:H7 percolates into a community's drinking water supply. Children and elderly people then drink the contaminated water which results in everyone involved contracting either dysentery and/or cholera and/or experiencing severe abdominal distress with most people infected thereafter dying a few hours or days later owing to a lack of resources, poor availability of healthcare and/or owing to already compromised immune systems, etc.
Kai Mikkel Førlie

Founding Member of Water-Wise Vermont (formerly Vermonters Against Toxic Sludge)
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  • goeco
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Re: Which composting toilet to choose - recommendations, please?

KaiMikkel, Wendy's system is no different from a septic tank feeding a soakage field. Except that humus is produced rather than sludge, which is a significant improvement. Now, we all know that soakage fields work when well constructed, but can fail miserably when poorly designed. Please keep the debate in context, it is fine for you to criticise soakage fields in general but there will be those who disagree and note that well designed soakage fields can be a component of good practice, safe onsite sanitation.
Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
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  • joeturner
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Re: Which composting toilet to choose - recommendations, please?

There is a difference when claims are being made about effective pathogen destruction which cannot be proved without rigorous microbial testing. And from our existing knowledge cannot possibly be true.

Systems exist. Yes. That doesn't mean they are safe.

I remain perplexed about how engineering solutions are prioritised over and above basic microbiology. Unless you kill the pathogens (with heat, acid, alkalinity, etc) if there is no testing of the output then there is an unknown risk of spreading them.

It surely isn't good enough to just assert things that a) are not tested and b) seem highly unlikely to be true.
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  • joeturner
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Re: Which composting toilet to choose - recommendations, please?

Furthermore there is quite a difference between a constructed soakaway and an openly draining pipe. Again, I am not an engineer and I don't really like either solution - however there must be a difference between installing a reasonably large engineering unit and telling unskilled and uneducated users that a pipe outflow is safe.
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  • goeco
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Re: History of vermifilter toilet and wikipedia article

Hi Wendy,
It doesn't matter how many holes there are and their size, once silt builds up inside the soakage lines, the system will fail, even with earthworms present. For longevity, perforated soakage lines require free flow of water to the holes, along with coarse media surrounding the line, with geotextile on top of the media and this covered with soil.

Please appreciate that percolation trenches are not secondary vermifiltration. Secondary treatment is a process to remove the suspended sediment, reduce BOD and pathogens, suitable for surface application. The thing about surface irrigation is that it can be moved to where you want it, to plants where nutrient-rich water is required. Because the nitrogen is retained using vermifiltration (unlike some treatment systems), and the phosphorous and potassium (along with other plant nutrients) are also leached into the water as the worms digest the solids, the wastewater exiting your system will actually be very rich in nutrients. Indeed all vermifilter toilet systems that I have set up using surface irrigation generate excellent plant growth. You may find that your lemon tree has not responded because of excessive water resulting from high subsurface water table (i.e. soakage field). Citrus require free drainage.

The vermifilter toilet "wheel" seems to get reinvented at regular intervals, but it is always good having different people looking at ways to improve it and open source their ideas. I started this thread because of frustration that people seem to be attempting to be claiming this simple, low cost technology as their own, clearly for pecuniary gain. For example "Walter Gibson, MA PhD, talks about his invention call "Tiger Toilet" The inventor of "Tiger Toilet" project, Walter Gibson, a microbiologist by Profession ..."  https://thewaternetwork.com/article-FfV/tiger-toilet-will-change-sanitation-thoughts-0KNfE2HCzVOMVSRVimsr3g

cheers
Dean
Dean Satchell, M For. Sc.
Vermifilter.com
www.vermifilter.com
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  • WendyHoward
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  • Biologist/ecologist/educator running a permaculture centre in Central Portugal. Came across vermicomposting/vermifiltration in waste management in 2013 and developed an open-source DIY system based on one pioneered by Anna Edey in the 1990s and using conventional flush toilets. Passionate about restoring life and health to the planet's ecosystems.
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Re: History of vermifilter toilet and wikipedia article

Please appreciate that percolation trenches are not secondary vermifiltration.


Mine are. They replicate the ecosystem contained in the primary processing unit. ie. organic (mainly woody) substrate which is colonised by the worms and their associated ecosystem.

Because the nitrogen is retained using vermifiltration (unlike some treatment systems), and the phosphorous and potassium (along with other plant nutrients) are also leached into the water as the worms digest the solids, the wastewater exiting your system will actually be very rich in nutrients. Indeed all vermifilter toilet systems that I have set up using surface irrigation generate excellent plant growth. You may find that your lemon tree has not responded because of excessive water resulting from high subsurface water table (i.e. soakage field). Citrus require free drainage.


With the greatest of respect for your experience and expertise, you do NOT know the details of my installation. I deliberately designed the soakage area to show up any nutrient release from the tank. There is no detectable amount. And neither would I expect any based on the lab results from Anna Edey's vermicomposting systems which show between 71-96% of nitrates removed by the ecosystem in the primary processing unit (see below).

I live on a terraced mountainside. There is no subsurface water table anywhere close. There is sloping bedrock around 1m below the surface, which conveniently channels any water reaching it forwards to appear half way up the wall of the terrace below. Thus I can monitor any seepage and its effect on the vegetation at the foot of the terrace wall. The vegetation there has not changed in 7 years. It's typical of an impoverished soil. When I say there's no detectable nutrient coming out of that tank, then I mean no detectable nutrient is coming out of that tank.

I don't know whether the systems you've worked with are based on largely inorganic substrates? Most of the published papers which I studied prior to designing this system were. This system is not. It uses organic material as a substrate and this is what makes the difference. That's why I refer to it as vermicomposting, not vermifiltration, because what is going on in that tank is far more than mere filtration. There is an entire ecosystem in there - essentially it's a replication of a large part of the soil microbiome - which has a major role in the bioremediation of wastes.

Further, the secondary metabolites of that microbiome have notable antifungal/antibiotic activity, meaning that faecal pathogens are also being dealt with.

I'm looking forward to working with my local municipality and the university department they select to monitor and evaluate the system. When we have some test results, I'll come back and post them here.

Quinta do Vale - Permaculturing in Portugal
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www.vermicompostingtoilets.net/
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