The first vermicomposting flush toilet system to be installed by the Câmara Municipal of Arganil was commissioned in July 2016. It was installed to replace a failing septic tank for a 2-person household in the village of Pai das Donas in the freguesia of Benfeita.
The system was closely modelled on the original system at Quinta do Vale which is close by. The container is built from concrete blockwork. As a retrofitted system, this one also has to deal with greywater, so the drainage pipework was installed with an option to divert water to additional ‘greenfilter’ soakaways if they were found to be needed.
As with the site at Quinta do Vale, the nature of this mountainous region with its steep slopes (averaging 30-45°) and thin soils makes it a particularly challenging environment for conventional septic tanks which rely on soil biota to treat tank effluent. Slopes are too steep and soils too thin to fall within recommended ranges for successful treatment. On top of that, the absence of any significant rainfall during the summer months combined with soils lacking in organic matter (and hence a dearth of soil life) frequently make for dysfunctional leachfields.
Not surprisingly then, the nearest stream evidenced septic tank pollution. The freguesia suspect the principal cause of the pollution in this stream is due to the failing septic tank of this household. It will be interesting to see how measures of bacterial contamination change over time once the vermicomposting ecosystem in the treatment tank has had a chance to fully develop. The water will be retested at this point. The initial readings were …
After 4 months, there was clearly a problem with the quality of the organic material. Most of what was initially added was hay, straw and leaves and this didn’t really provide enough substance to make a suitable substrate for the ecosystem to start to develop, or to act as a proper filter. When we inspected the tank at the end of November, we could see it wasn’t functioning properly. The hay round the edges was still fresh and hadn’t been incorporated with the material in the centre, and we couldn’t see much evidence of faecal material or worms. The tank was refilled, using a good proportion of partially decayed wood chippings plus autumn leaves, and more worms were added.
The good news was that the tank enclosure had finally acquired its roof.
We inspected the tank again after another 4 months. This time all was as it should be and functioning well. There was no hint of odour and faecal material was clearly being consumed at a satisfactory rate by the worms. No additional organic material was required at this stage.
We noticed the grass at the base of the wall on the terrace below the greenfilter was growing much more vigorously than the grass further out on the terrace. We suspect this was at least in part because the tank wasn’t functioning properly to begin with and fertility in the form of nitrates was finding its way past the greenfilter. To some extent, this is to be expected initially since the vermicomposting ecosystems, both in the tank and in the greenfilter, take time to develop. But this is something to be monitored, because this tank processes grey water as well as black water and it’s possible the one greenfilter alone isn’t sufficient. It does show how easy it is to spot when something isn’t working quite right though. If we notice a continuing lushness in the vegetation at this spot, a second greenfilter will be dug here to process what is escaping the first.
Hi, thank you for all the wonderful information I look forward to helping add to that in the future. Have a question about the second Greenway. Are you going to build the greenway beds so that the contents from the first one overflow into the second, or are they separately plumbed greenways?
Do you think that the excess nitrogen escaping is due to lack of filter space in the one box, or do you think it’s caused by not enough square footage in the Greenway?
Either reason will require additional capacity to except the gray water as well as black water.
Sooooo we either need to build additional worm bin and add to the same green way, or just one worm bin and add additional greenways that flow into each other or are separate beds.
If you had to do this already would you mind showing pictures or Instructions on how you set it up and how well it worked out.
Thanks so much. I start contruction of our vermiculture septic this week. Ill document with pics and submit when complete. I look forward to contributing to this knowledge base.
Hi Paul. Thanks for your comment and really happy you’re going to be building one of these systems. Look forward to the project details!
The second greenfilter (if we need one) will be separately plumbed so it shares the outflow from the worm bin equally with the first greenfilter. The greenfilters aren’t lined or contained in any way so there’s no way we can collect the water from the first to pipe it to a second. We had a very dry winter, so it’s debatable at this stage whether the lushness in the grass on the next terrace is because the worm bin wasn’t functioning properly initially (which is what I suspect) or whether the first greenfilter isn’t adequate. We will need to monitor it for a while to determine this now that the worm bin is working as it should be. It’s possible we can expect to see better growth in the vegetation on the next terrace purely because there’s water becoming available where previously there was none. Soils here are shallow and the slopes are steep. We can expect the water to work it’s way downhill regardless. The crucial question is whether or not it’s being properly cleaned. If any nutrient is making its way through the system, then I would expect to see changes in not just plant growth, but also in the plant species growing in this location reflecting the higher nutrient availability. So far there isn’t. Time will tell …
The excess nitrogen escaping was purely down to an inappropriate mix of organic material in the worm bin (as stated in the project report). It just wasn’t providing the right substrate on which the ecosystem could develop. Not enough slow carbon – wood chips primarily: things that take more time to decompose. Too much fast carbon – straw, hay, leaves. My experience with my own system tells me that if it’s working properly, then next to no nitrates pass through the worm bin. Certainly not enough to impact the vegetation. So with the Pai das Donas installation, I will be expecting to see effects consistent only with the provision of a degree of irrigation. If this is all we see (ie. no change in species distribution) then I would consider a second greenfilter unnecessary. In other words, if all we’re getting is clean water working its way downhill, then there’s no necessity to clean it further.
Does that all make sense to you?
…absolutely makes sense. Now if we can get the county to agree on that we’ll be able to get these permited in the US. I have found human waste to be one of the larger challenges of living off grid. We live on ten acres in the mountains of Santa Barbara and have very similar geographical limitations that you’re up against. We also have very dry summers in the soil tends to harden up. The VCS system seems to be beneficial all the way around, i just want to get on a soapbox for telling everybody about it. It is such a game changer for us.
One thing that I am cautious about, is the proximity we are to a seasonal Creek. Do you have any thoughts on that or setback distances etc.
Additionally I would like to run gray water from showers sinks but also washing machine, which may amount to quite a bit of water. At the risk of asking a redundant question, do you think there would be a need or benifit for two separate systems? One thought is that of the system were to be overloaded, at least the bathroom side of it would still be operational.
I was also wondering if you Have you ever had the toilet stick on and keep running and flood the system?
Thanks so very much for your time, we appreciate it immensely.
Ha! I think getting the system permitted and promoted at the moment is more likely to run up against the fact that it’s not a big money-spinner for some corporation than that the science is suspect. Thankfully that’s changing. Or will be soon.
Running grey water through the system isn’t a problem, but it’s possibly a bit of a waste in your situation. Grey water is too useful for irrigation! Check out Art Ludwig’s Branched Drain and Laundry to Landscape greywater systems. He runs Oasis Design and has done a lot to get these systems code-approved in California. He’s also your neighbour as he lives in the mountains behind Santa Barbara!
Being next to a creek isn’t a problem. Once the ecosystem in the tank is up and running, the water exiting the system is cleaned of upwards of 90% of all pollutants. Anna Edey, who’s system I based this one on, devised a similar setup to process all grey and black water from the Black Dog Tavern, right on the harbourside in Martha’s Vineyard, MA. That was handling 15-19,000 litres a day! Details of her project here. Test results here.
As for flooding the system, the only way that’s possible is if the exit to the tank blocks. Otherwise the water just runs straight through.
PS. If you want to help promote the system, The Regeneration Hub are presently looking for 5 projects to receive a micro-grant of US$1000 and support from leading regeneration experts. This project meets all their criteria, but they are also looking for evidence of public support. You need to register on the site to access the comments section at the bottom of my project, but if you comment using the hashtag #RegenerationInnovations and say why you think the project should be selected, it will be a great help!
We are just starting to build in Sobral near to Gois copying what we have learnt from these sites and permaculture mags ,the people helping me will also be building them too .taken me 3 years to persuade my husband.will take pictures and report back .or contact if we have problem . We also wanting to use for grey water as we suffer from lack of it high up in sunny Portugal .we had got separate tank to use for it as did at realise we could use the same tank , so that gives us another tank to build with for our second out door bathroom .we all buzzing from creating this form of waste management .having lived with dry compost loos for too long .
Hi Jane. You’re not so far across the mountains so you’re welcome to come to Benfeita and see the system here if you want. It’s not necessary to take grey water through the worm tank. Here you can take it straight to irrigation. It’s advisable for the output from the washing machine at least – the fats in laundry detergents can sometimes cause problems.
First of all, thanks for this super website and complete information! Much helpful!
The size of the tank we are building here is only 0.77 m3.
Will it be enough? This is for a small family house.
What are the dimensions of the tank? And how many people are in the household?
Ive found this a teally useful website, thank you!
Two questions please!
1) whay size of mesh is used?
2) would the use of a black ibc tank ( which i can obtain) have any benefits over the usual clear / transluscent ibc tank?
Please use the forums for questions like this. That’s what they’re for!
Mesh details are on the Design and Construction page. A black tank, so long as it’s food grade plastic, would be fine. There are no benefits to it over the normal ones. It would work just the same.
Hi Wendy! Thank you so much for creating this site, and sharing all of this wonderful knowledge! Here in Texas, the waste water treatment department for the state has a sub department, where you can submit ideas for on site sewage facilities (OSSF). It has been over a year since I submitted your plans and info, along with my other research. It is helpful that several national parks already have composting toilet systems, just not with the flush toilet model. I have been in contact with the director of the tecq department and she seems to think this system might be able to get a provisional license! I’ll keep y’all posted!
April that’s great news! Yes – please keep us informed!
I want to build a similar system like yours. Do you think it’s possible to visit you in Benfeita?
Thanks. Have a nice week 🙂
Sorry I only just saw this comment. You can arrange to visit, yes. Details are here – https://www.permaculturinginportugal.net/learn-with-us/visit/