Vermifiltration mantainance

[Dahlia]

Hello everyone, im doing my phd and also have a small company all about nature based solutions and very focused on vermifiltration systems in Mexico. I have found different information about the maintenance and I’m unsure if 1) one should completely empty and refill the organic matter or wood chips from time to time, 2) how often the vermicastings should be recovered 3) what is the best method to do so and. 3) what type of wood shavings are you using ? I have read that pine shavings could contain phenols and resins which are not very good for earthworms and can decrease the pH, but I have use them with no problem so far but I would like to know which type of wood shavings are you using.. and finally 4) how often do you refiill the system.

Thank you so much for your help, I’m looking forward to rad from your expertises. 

[Kimi Ishikawa]

We have a pretty new system in the style of vermicompostingtoilets.net so I don’t have a track record yet, but my understanding is that it should never need emptying and you don’t harvest the vermicompost. You only add browns periodically to help balance the C:N ratio. The good stuff heads out to the drain field. That website has lots of good info on maintenance. My website BrownKawa.com also lists some other peer reviewed research papers in the FAQ and Resources sections. (My site is much more broad and does not hold a candle to Wendy Howard’s vermicompostingtoilets.net, but does have a little info on our system & those research papers that we used to get our permit.)

It does seem odd, because the water that comes out should be pretty clear, I think, so I don’t know what happens to the vermicompost. Maybe the microbes fully break it down into soluble stuff??

In any case, I hope that is how it works, because it would be a big mess and would disturb the whole ecosystem to dig down to the bottom of the IBC tote to access the vermicompost with fresh wastewater being added all the time? I suppose if you had a 2-tank system you could leave the unused tank to process for a while and then harvest… we have only had the need so far for one tank, and that’s all we anticipate needing.

My understanding is that some commercial systems in Australia had an auger-type system that would bring vermicompost to the surface, but I have also heard that some of their systems had problems with contamination and fell out of favor. I don’t want to risk any of that type of situation.

Re: materials… I live in a very dry piñon/juniper woodland, so only have those woods to work with. They work great. We used big branches, small branches, and filled in with chipper-shredded chips. So far we have topped off with straw or shredded cardboard, just because that’s what we have available. I supposed if you live in a place with lots of hardwoods, leaves, etc. you might have the luxury of being picky, but where I live everyone composts with pine and juniper and you should just use what is abundant in your area.

Good luck, and it would be great if you could keep us posted on what you learn!!

On Sun, Nov 30, 2025 at 6:52 PM Dahlia <dahlia.del...@gmail.com> wrote:

Hello everyone, im doing my phd and also have a small company all about nature based solutions and very focused on vermifiltration systems in Mexico. I have found different information about the maintenance and I’m unsure if 1) one should completely empty and refill the organic matter or wood chips from time to time, 2) how often the vermicastings should be recovered 3) what is the best method to do so and. 3) what type of wood shavings are you using ? I have read that pine shavings could contain phenols and resins which are not very good for earthworms and can decrease the pH, but I have use them with no problem so far but I would like to know which type of wood shavings are you using.. and finally 4) how often do you refiill the system.

Thank you so much for your help, I’m looking forward to rad from your expertises. 

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[Dean Satchell]

Hi Dahlia, welcome to the group.

Pine bark is the absolute best media, because it resists decay and you want a permanent substrate for the worms to live in that doesn't rot away. In contrast wood chips of the same size as pine bark decay very fast and wood shavings decay even faster. Once the humus builds up enough (from many years of use) this becomes the media, but until that happens your substrate needs to last the distance. I've found 20cm of pine bark does last the distance, whereas pretty much any other form of organic matter decays too fast and you risk not having sufficient substrate to filter properly, and it would be pretty messy to try and add to the substrate with a pile of fresh poos on top. Pine bark is usually available in different grades, for the primary vermifilter I use a fairly course grade.

Keep in mind that the primary vermifilter doesn't need to (and won't) remove all the solids. Suspended solids do make it through. This doesn't matter because if you have a soakage trench then the suspended solids decompose in that. Septic tanks usually discharge less suspended solids to the soakage trench than primary vermifilters, because septic tanks settle the solids rather than filter them. I settle the solids coming from the primary vermifilter and recirculate them back into the primary vermifilter, and follow with a secondary-treatment vermifilter so that I can discharge my treated effluent to the soil surface.

Always build twin primary vermifilters. This is important because you only want to remove humus from a well rested digester. Roundworm eggs take years to die, and composted faecal matter (lets call it humus) should not be put anywhere near gardens unless it is rested for a number of years. You shouldn't ever remove the bark/humus substrate, and I've found it unnecessary to remove any humus for at least a couple of decades. You can remove humus if you want to use it though... but again twin primary vermifilters are a must if you want to harvest humus, so you don't need to go near fresh poo. Eventually the single primary vermifilter will become a problem, even if that is someone else's.

Kind regards

Dean

[Dahlia]

Thank you so much Kimi for your great answer. 

So, I have a pilot wwtp first stage are vermifilters (3 in plastic 1100l containers) and the second stage are constructed wetlands. They treat institutional wastewater (95% blackwastewater) from two small buildings in where I do my PhD… 

(By the way I do not recommend having them in this plastic containers because of the difficult mantainance, definitely the two chambers vermifilters are the best) 

I’m evaluating different two substrates: first vermifilter has coconut shell nuggets, second has pine bark and the third one a mix of both. We have available this substrates in the region so we wanted to evaluate them. I just had a problem at the beginning because of the tannins and for couple weeks the water was very very dark but after it washed and was very clean. 

 

Honestly I didn’t till the vermifilters in 6 months I think that’s why they clogged (of course). And I used sawdust because the pieces of coconut and bark were quite big (3- 5 cm) so the HRT was small, this do helped increasing the HRT but then it clogged the system. 

 

However I have find that some never empty the vermifilters, others say if you don’t so, the vermicompost or castings will become so small that they sink to the inorganic layer and clog from the bottom, some just remove the first cm every 6-12 months. Of course if you plan to sell or to use the castings it makes sense. So far we remove a little bit of mud and system is working apparently normal. So I will wait unitll january to make the second laboratory analysis and as far as we have the one year analysis i will be very happy to share the insights with all of you. 

Its very intersting that you never remove the vermicompost... and how old have been your previous systems that have opperated under this non-removal of vermicastings? just to know if you have experienced this issue of clogging the inorganic layer?

Thank you again Kimi for taking the time to answer. 

[Kimi Ishikawa]

Thank you for your kind words, Dahlia! Your setup sounds impressive.

Our system is brand new, so I don’t have a track record to share, but if you look on vermicompostingtoilets.net, that type of system has been in use for decades without removing compost. I know I would not want to use compost on my garden taken from the top of a septic tank…!

Most folks on this forum use a completely  different type of technology, so you can take it with a grain of salt if they comment on how they think mine will or won’t work… 

I’m al all for everyone working to move vermiculture septic forward like you, like everyone on this forum, like Wendy Howard and her vermicompostingtoilets.net, and like the many researchers around the world. But I know I am not qualified to evaluate technologies I am less familiar with. I only know what we are doing, and we will be doing effluent testing quarterly so in a year I should have some data to share on our system, and in ten years I will be able to tell you whether mine can really work for ten years without removing compost ;D until then, I am trusting in Wendy Howard’s work that it will.

What do you have in the bottom of your tank? How does water drain? I am puzzled by the maintenance and clogging.

We have a layer of gravel at the bottom. I don’t remember offhand how thick, but maybe about 10”. Our water flow is through a 4” (~10 cm) perforated PVC pipe that downsizes to 2” (~5pm) at the bottom. This whole outflow pipe is wrapped in nylon screen. The pipe protrudes from the top of the medium, but the perforation doesn’t come up to the top, so the water is flowing out from the~30cm or so below the solid wastes. The smaller part of the pipe at the bottom is completely embedded in the gravel layer. I hope it doesn’t clog! Sorry you had to deal with with that.

Good luck with your work!

[Burton & Cherstin Sparks]

Dahlia,

Some thoughts from someone who has studied but not implemented yet. Designs like those at vermicompostingtoilets.net rely on treatment from the primary vermifilter (higher HRT from finer biodegradable media) and a shallow absorption field (same vermifilter media in the absorption field).  Designs like Dean's at vermifilter.com rely on the primary vermifilter mainly for filtering (non-suspended) solids (lower HRT from media that is more coarse and slower to degrade), and use the secondary vermifilters for treatment (higher HRT achieved by recirculation).  I've heard of a group that is moving toward entirely non-biodegradable media.  Whether you need to empty a bin will depend on the rate the media degrades, the temperature (how fast the worms can work), the size of the bin for the number of users, and whether toilet paper is used.  The impression I get is that fast biodegrading media without toilet paper can probably have the smallest primary vermifilter bin without needing to be emptied, and even non-biodegradable media with coarse media would not need emptying if the bin is large enough, but most everywhere in between those you'll need to empty sooner or later.

What did you mean by "do not recommend having them in this plastic containers because of the difficult mantainance"?  Are you saying there is poor access, or something else?

Burton

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[Dean Satchell]

Hi Dahlia,

A good primary vermifilter is a geotextile cloth-lined basket held within the container, with a cavity right around the outside of the basket and underneath it. A vermifilter must be failsafe - the last thing anybody should have to do is unclog it. The cavity is essential not only for keeping the vermifilter aerobic and ventilated, but also to avoid what you describe as "clogging". I'll define clogging as where HRT is greater than HLR (i.e. too many users for that VF). You require a substrate coarse enough to drain well, but also understand that the mix of toilet paper and poo sitting on top of it won't drain very well, and if you keep adding more (with lots of water), this will create a dense layer that will impede drainage, i.e. "clog" and the water will sit on top and the worms will run out of air and die. If this occurs in a textile-lined basket, the surplus water can exit out the sides and drain away, and the cloth will keep the solids inside the basket. A primary vermifilter basket should have lots of width (surface area). 

You'll need research results that are not confounded by what is going on above your substrates. There should not be any "mud", which suggests anaerobic. Remember that your worms live in the substrate (which must be aerobic) and they eat the solids from underneath, that are deposited from above. If you are studying the coconut and bark substrate, and if it is too chunky, then screen it to remove the larger chunks, and if necessary grind it up a bit. You want an average piece size of 1-2cm, 20-30cm thick. You could experiment with these variables, they are likely more important than pine vs coconut. The substrate must drain well, but it also shouldn't be too coarse, which would not filter. There is a sweet spot that your study should target... Sawdust is too fine for the substrate.

Yes, over time the substrate ends up becoming humus, but that will be long after your PhD is finished. The worms live in this humus and it is free draining and provides the same function as the bark that was put in place to get things going.

Cheers

Dean