Frequently Asked Questions

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Vermicomposting is composting using worms, and a vermifilter is a filter using composting worms and their bedding. A vermifilter septic system is, therefore, a septic system that uses a filter of worm compost and bedding to process household sewage.

Our system will use a living ecosystem featuring composting worms to process our household wastewater, in lieu of a conventional septic tank. Our raw sewage will run through a vermifilter made up of carbon-rich organic materials (e.g., wood chips, straw) and vermicompost. The solids will be caught on the top of the mulch pile, while the liquids flow through the wood chip filter for processing. The worms consume the solids, and host a rich community of beneficial microbes. The worms work through the wood chip bedding creating voids that retain water for thorough processing by the microbes. The entire ecosystem processes waste by consuming the waste, consuming pathogens, and filtering the water through the organisms’ bodies, thereby improving water quality. Resulting effluent flows from the vermifilter septic tank to a vermifilter drainfield. The drainfield is a trench the same size as a conventional drainfield, but filled with wood chips on top of a gravel base. Pipes will distribute the effluent throughout the drainfield which will thereby populate the drainfield with a beneficial microbe community similar to that within the tank, and plantings in the drainfield will further process the water, taking up remaining nutrients and transpiring moisture. Our system is based on the open-source system found at vermicompostingtoilets.net. We modified it to better fit with New Mexico requirements when possible, and to tailor the design to our location and application.

We will be testing our filtered effluent throughout the year and sharing the results with the New Mexico Environment Department. We are required to test for Total Suspended Solids (TSS), Biological Oxygen Demand (BOD), and Nitrogen. For our own purposes, we will also test for Coliform Bacteria, e. Coli, and pH. We will start testing quarterly, and requirements for testing beyond that will depend upon the results. If results are worse than those expected from primary treatment in a conventional septic system we will have to remediate and retest. If we are unable to get results that are at least as good as those required for a conventional septic system we could be required to remove our vermifilter system and replace it with a conventional septic tank and drainfield.

According to the peer-reviewed scientific research articles from around the world that we submitted with our application, our system should easily outperform primary treatment by conventional septic systems. Conventional septic tanks expect a 20-50% reduction in Nitrogen, BOD and TSS. Research shows reductions of 90% in BOD and TSS, and 70-80% reduction in Nitrogen with vermifilter systems.

The original design on which ours was based was pioneered in Massachusetts decades ago, but is not approved there, to our knowledge. The design evolved into that described at vermicompostingtoilets.net, which is legally implemented in several jurisdictions in Portugal. The research papers we found and included in our application describe systems in use in India, Iran, Australia, and New Zealand. Commercially manufactured systems are available in Australia and New Zealand. Large-scale vermicomposting systems are used to process dairy and winery wastewater in the United States. Vermicomposting is used in at least one local jurisdiction in Pennsylvania to process sludge remaining from conventional wastewater processing. People have installed non-permitted vermifilter septic systems similar to ours in the United States, in areas without local oversight, or “under the table” at vacation properties and the like (as found through YouTube videos or in off-grid forums). After receiving our permit we learned that there have been at least two pilot vermifilter sites sanctioned by the Hawaiian government, which is working to get rid of all cesspools in Hawai’i. We are not aware of any other state-sanctioned vermifilter septic systems in the United States, and applaud New Mexico for taking this forward step. If you are aware of any other permitted vermifilter septic systems in the U.S., we would love to hear about them! Update: Another system has since been permitted in Wyoming! They will eventually be posting about it at https://www.peacefulvalleyfold.com/

Conventional wastewater treatment results in noxious sludge that must be removed. This system does not produce any sludge. The solids are completely consumed by the worms and the rest of the ecosystem. Conventional wastewater effluent has pathogens in it that are usually treated with chemicals in municipal systems, or further treated in drainfields in conventional septic systems. The vermifilter septic tank produces wastewater with 99% of the pathogens removed, according to research. In our system this effluent will be sent to a drainfield with conventional sizing, but the quality of the water reaching the drainfield should be much better than that from a conventional septic tank. In some other countries the effluent is even used for irrigation, since it is so clean. To be clear, we will not use the effluent for agricultural production, and will not collect any effluent (except for required test samples). All emitters will be under the surface, in mulch. We will be planting grasses, flowers, and shrubs to support pollinators and other wildlife. From an economic standpoint, our system will be much less expensive to build than a conventional system. The tank will not need to be buried, and will be a simple recycled water tank. This is a low-tech solution with advanced potential. It is a great option for on-site wastewater processing and is therefore ideal for New Mexico which has many low-income rural and remote residents.

The system requires management. You can argue that it is lower-maintenance than a conventional system, since there is no sludge to pump and its natural processes are more effective at treating wastewater than conventional solutions. But it is also a living ecosystem. A householder needs to be aware of the living worms and take steps to protect them in extreme weather situations or during vacation absences, and to add carbon-rich organic materials every few months to balance the high-nitrogen wastewater. You need to monitor for any plumbing issues, to make sure the system doesn’t back up, drowning the worms. It is no more difficult than monitoring your home’s plumbing and heating systems, but there is no infrastructure of vermiseptic maintenance companies out there to call upon. For this reason, it may not be the ideal system for homeowners whose idea of home maintenance is to call the local handyman. Since it is a living system, it is also not ideal for vacation properties that are rarely visited or used.

The process we went through is not for the faint-of-heart. It is such an unusual request, outside of the norm of the permitting process. The permitting process took over a year from the date of our first application until the permit was in hand. Before we submitted the permit, we had been researching alternative septic options and planning (in the background of other house-building tasks) for an additional couple of years. Our system will be installed on a 140-acre property. The closest full-time neighbor is more than a mile from the experimental system. The closest property line is more than 100’ from the system. All neighbors are supportive of this work. The remoteness of our installation likely made it easier for the state to approve this experiment. We initially applied through the process for getting an experimental design approved. Our application was over 100 pages long and included a design document, user manual, research papers, site plan, and several bureaucratic forms including a complicated checklist of requirements. We went through months of waiting, phone calls, emails, meetings, and two reviews. We then needed to re-couch the application through the Variance process. This required many of the same materials, but a different set of bureaucratic forms, a notice letter to our neighbors, proof of notification to our neighbors, and a different set of checklists. This application was sent as 19 PDF files, and was followed by more months of phone calls, emails, waiting, and finally, a site visit. And then… an invoice, the payment process, a few more days, and then we received our Permit to Construct!

Of course! Here are some of the lucky aspects in our process: As a Virgo, I was born with an unreasonable affinity for filling out forms, investigating complex parameters, and trying to figure out unconventional workarounds. The several New Mexico Environment Department staff members that we worked with were each encouraging and positive about our goals, even though they were also extremely busy and our unconventional application surely posed a puzzle that was difficult to fit into place within their mandate. I am a retired teacher and my husband Chip is a retired state regulator, and we are both intimately familiar with bureaucracies. That kept us from getting as flustered as we might have otherwise been, and definitely helped us stay polite and “patient” throughout (even though we might have expressed some impolite impatience in private!) Our backgrounds also taught us to be persistent and tenacious. It helped hugely that Chip is a hands-on hard worker and was very supportive of me spending countless hours on the computer while he was out in all kinds of weather keeping our camp running and building our house, without making me feel guilty. And I hate to say it, but one “lucky” thing for the experimental septic effort was that our house build kept taking longer and longer than we expected. At the end of 2021 I promised Chip that if we didn’t have a worm septic permit in hand by May 2022, we could throw in the towel and install conventional septic. But we weren’t anywhere near ready for septic by then, so kept pushing ahead, and finally started building our conditionally approved system in April, 2023!

All things being equal, we generally prefer to follow the law. We do realize that, given the complex hoops needed to follow the law combined with the minimal regulation and oversight in our rural county, some people would not consider all things to be equal; so I will go into our other motivations as well: The main reason is that we believe in this technology and were willing to jump through the hoops. We do care about having this technology available to us (which we could arguably do illegally), but we care equally about promoting this technology so that it might become more available to others, and more accepted within the United States. This should provide better wastewater treatment, in a more sustainable way, and at a lower cost than conventional wastewater processing. This technology has been around for decades and is being implemented around the world. Why should the United States (where our type of system was innovated in 1995) be stuck in the past with outdated chemically-dependent, sludge-producing methods of wastewater treatment? We also have a permit for our house (the first Tire Bale house to receive a permit in New Mexico), and we need a permitted septic system for that. We for sure don’t want to install a conventional system if we don’t have to, so we wanted a permit for our experimental system. [To answer the obvious follow-up question, we wanted the house permit (even though we probably could have gotten away without one in our remote area) for the normal reasons – to make it easier to insure, easier for our heirs to sell to someone needing a mortgage, and to comply with the law. We also wanted the house permit for similar reasons to the vermifilter septic permit – to promote the use of tire bales in construction (which is a whole ‘nother story). And beyond those reasons, we would be unable to get the tire bales without a building permit, since tire disposal is highly regulated.]

Our application forms would not be useful for other applications since they are so specific to our site and to New Mexico requirements. It is also premature to share our as-yet unproven system: we haven’t yet built it, and even once we’ve built it we will still have to test it for at least a year to make sure it works as promised. I do look forward to getting our (hopefully positive) data out there along with build photos and any other information that is helpful once our system has been fully approved. At this time, I am very happy to share the resources that we found – those were extremely valuable in putting together our application. The most useful portion of our application is likely the user manual, derived directly from vermicompostingtoilets.net which is probably a more relevant reference than our specifically tailored version. We also pored over many scientific research papers and whittled down to #1-5 below which were included with our application. The abstracts or full papers are all available online without subscriptions. The key backbone of our application was Wendy Howard’s great work, #7, which she generously shares open-source. We found it helpful to annotate the key points and non-applicable points in our application to help focus reviewers’ reading, so I share that below as well. 1. Sinha et al, Griffith University, Queensland, Australia (2008) Sewage treatment by vermifiltration with synchronous treatment of sludge by earthworms: a low-cost sustainable technology over conventional systems with potential for decentralization. The Environmentalist This primary research paper is referenced by many other papers on the topic, indicating its wide acceptance. It describes a controlled experiment and discusses the results in a wider environmental and economical context. Key applicable points: This gives an excellent overview of the many benefits of earthworms as applied to biofiltration of wastewater, detailing the many mechanisms in this odor-free process resulting in clean water disinfected enough for reuse in agriculture, parks, and gardens. The paper notes the lack of sludge using vermifiltration, and quantifies the level of treatment attained. Suspended solids were removed by over 90%, resulting in no sludge. Turbidity was removed by over 98%, pH was almost neutralized, BOD loads were removed by over 98%, and COD was removed by 80-90%, through enzymatic action. The paper also explains the earthworm life cycle and interaction with its environment, emphasizing that the population can adjust to the variable wastewater environment due to worms’ ecological adaptation abilities. Aspects not applicable to our design: The researchers also discuss processing of toxic wastes which is far beyond the expectations of our small household septic application, and we do not aim to use the water in agriculture, parks or gardens (other than our drainfield wildlife garden). 2. Arora et al, Indian Institute of Technology, Roorkee, India (2014). Pathogen removal during wastewater treatment by Vermifiltration. Environmental Technology This primary research paper quantifies pathogen removal from wastewater in a vermifiltration system and explores the mechanisms behind pathogen removal. Key applicable points: The study found that BOD was reduced by 84.8% and COD was reduced by 73.9%. They go on to quantify the impressive removal rate for various pathogenic indicator organisms, and explored further to identify and analyze antibacterial microorganisms symbiotic with earthworms found within the vermifilter bed. They conclude that vermifiltration removes over 99% of coliforms from wastewater and therefore provides primary, secondary, and tertiary treatment (disinfection) in one. Aspects not applicable to our design: The experimental treatment bed in this study used almost 50% inorganic filtration materials (gravel and sand) and 50% vermicompost. Our design uses a smaller layer of gravel, and the vermicompost includes a deep layer of organic filtration material such as wood chips. Our system is only aiming for primary treatment at this point, although impressive results like this would certainly not hurt our system. 3. Gupta, ABES Engineering College, Ghaziabad, India (2015). A Review on Effectiveness of Earthworms for Treatment of Wastewater. International Journal of Engineering Development and Research This paper provides a literature review of several studies from 1991-2014 of vermifiltration of wastewater from various applications. Key applicable points: Domestic wastewater study showed BOD reduction of 85-93% and COD reduction of 74-80%. A different study on rural domestic waste water showed COD reduction of 81.3%. The paper also gives a succinct overview of earthworm ecology, biology, economic significance, earthworm mechanism in wastewater treatment, and the synergistic action of enzymes, microorganisms, and earthworms, based on the literature review. Aspects not applicable to our design: The paper also summarizes results in the gelatine industry, palm oil mill effluent, dairy industry, and treatment of sludge, all irrelevant to our household septic system application. 4. Taylor et al, University of Queensland, Australia (2004). Characterizing The Physical And Chemical Properties of a Vermicompost Filter Bed. Compost Science & Utilization This primary research paper focuses on analyzing the composition and properties of the vermifilter bed. Key applicable points: The study found that the vermifilter bed naturally develops unique filtration properties such as high wastewater retention time and complex flow characteristics due to the action of earthworms, far greater field capacity than is possible with inorganic filter systems. Aspects not applicable to our design: The system described diverges from our design in some key ways. The tank is fully submerged underground requiring a wind ventilator, while ours is above ground and vented directly to ambient air. There is no aeration and drainage tube within the vermifilter bed in the Australian tank as there is with ours. The described tank is designed to take all household organic waste including kitchen scraps, newspaper, and cardboard, while ours is designed for household sewage only. The described tank therefore has a buildup of compost and requires an auger to remove compost through the top of the tank (where unprocessed waste is deposited). The system described is commercially available in Australia but not in the United States. 5. Yadav, K.D. et al (2011). Vermicomposting of source-separated human faeces by Eisenia fetida: effect of stocking density on feed consumption rate, growth characteristics and vermicompost production. Waste Management. This abstract simply describes the optimum stocking density of worms for processing wastewater. Key applicable points: .5 kg is appropriate for bin startup, as the worm population grows rapidly. 3 kg of worms is optimum for full production in processing sewage. In this study the worms ate a maximum of 40-45% of their body weight in human feces per day. Aspects not applicable to our design: We did not have access to this full article but included it as justification for the .5 kg initial stocking minimum described in our manual (which is also the amount used in Reference 7). 6. “Happy Worms All Winter Long!” article by Sam McCarthy from NM Healthy Soils website. This article describes how to maintain earthworms through winter. The author raises earthworms in the Santa Fe, New Mexico area. Key applicable points: With enough bedding volume, food, and water (conditions similar to our design), the author finds that earthworms maintain their activity throughout the winter. Aspects not applicable to our design: Our design has additional supports for the worms, since the bin is housed in an insulated shed which would protect it further from the elements (both heat and cold). 7. Vermicomposting Toilets Design and Construction, and Function and Maintenance manuals from http://www.vermicompostingtoilets.net. Finally, this critical, thoughtfully developed and referenced website provides the open-source design and use documents on which our design is based. Other sections of the website discuss the history and various aspects of vermifiltration. This website is maintained by Wendy Howard, who brought the technology to Portugal and worked for its acceptance by building departments in communities there. Key applicable points: There are strong parallels between our highly derivative manual and this site’s design and construction and function and maintenance web pages, both of which form the basis for our manual. The whole website provides context for our efforts. Aspects not applicable to our design: Our document was modified to meet New Mexico requirements and to focus on the combined greywater/blackwater portions of the website, since New Mexico requires our system to handle all of the liquid waste on our site (even though our house is also plumbed for greywater diversion).

We will for sure have layer chickens, which we also had in Wisconsin. We hope to have honeybees, but that probably won't be until our second year. By then we should have enough citrus growing to keep them well-fed! We are considering having meat chickens, and maybe rabbits... we did help out with chicken slaughter at a local farm to see if we were up for that. Our conclusion was that we are able to do it, but do not want to do it for a business. If we did that it would just be to feed ourselves and our guests. We don't have any plans to go beyond that. We aren't planning on goats or sheep or pigs or a horse or donkey, but we've toyed with each of those ideas and haven't ruled them out. Maybe eventually if we have more neighbors or like-minded neighbors we could get some community animals so we'd have a share in the work and bounty but could still go on trips now and then! We definitely wouldn't get cattle.

We'll have a number of growing areas... In the greenhouse we'll have tropical fruits [https://www.brownkawa.com/post/planting-plans https://www.brownkawa.com/post/wrap-up] We'll also grow cool-weather annuals in the greenhouse in winter (brassicas & greens) and warm-weather annuals in summer (melons, peppers, tomatoes, cukes). We plan have an outdoor garden with more traditional local plants (regional squashes, melons) and also general hardy shorter-season plants like radishes, greens, brassica). We hope to have an outdoor orchard on a slope, bermed to capture water but also irrigated when necessary (sour cherries, apricot), and some drought-tolerant trees in other areas (jujube). ...and we could go on and on about various plans in our head, but I'd better stop here before I move into the areas that we likely won't be doing for the first few years!

We do have surges and stops. Recently we've had lots of stops due to weather or holidays or contractor schedules, etc. Then when that slow-down is over, we're eager to jump in! But for example, once we were done filling the trenches, I had a definite feeling of "OK, now it's on us -- nothing stopping us from finishing quickly; no more excuses!" I figured we could get an early start the next day (yesterday) and just whip out the frame. The result of that is that I was compelled to stay up until 1:30, sleep in, then "needed" to do dishes and bathe (at least a monthly requirement, hah!) before heading over. So all we did was move the frame over and try that one end piece out for size. So for us it doesn't feel like we are able to "keep going" -- more like we go in fits and starts. For me the challenge is to be kind to myself when I have one of those Kimi-induced (rather than weather/contractor/etc-induced) slowdowns... and to be kind to Chip when it's a Chip-induced slowdown! We are retired, after all! :D

We will capture rain off of the greenhouse "roof"(/walls). It's not designed perfectly for that (no eaves) so we'll probably have to do something goofy like screw a gutter toward the bottom using the same screws that affix the lexan, and then silicone-seal it to the lexan face... On the back it will be easier because the siding has bump-outs, so we can at least put the gutter below a lower bump-out. On the other hand, the siding is installed horizontally instead of vertically so I'm not sure how nicely the water will flow. We'll also be capturing and reusing graywater. And eventually we hope to have a small aquaponics system inside for some of the growing (greens and such), and that will recirculate water. It might be too much for this first year, though -- not sure when we will get to that. This year we plan to put a bathtub in! Then we could use that for fish after we have a bath in the house... and yes, the bath water can water the trees! Outside, we will chip wood to create on-contour berms to slow down runoff and incourage infilteration, and we will plant fruit trees above each berm (well, we might berm in other places without planting as well. We don't plan to capture water after irrigating -- hopefully we'll mostly be watering just enough that the plants will take up and use what we give them!