Updated: Oct 3
We are now building an experimental vermifilter septic system
You read that right: a vermifilter, vermicomposting septic tank, wastewater greenfilter... a worm septic system! The septic tank is filled with wood chips topped with worm compost. You run the sewage into the top of the tank. The solids are caught on top while the liquid filters through the wood chips. Worms eat the solids, and their microbial community eats the pathogens.
Worm septic systems work
According to peer-reviewed research in scientific journals across the globe, by the time the water has filtered through the top half of the bed it is far cleaner than effluent coming out of a conventional septic tank, and the water that comes out of the bottom valve into the infiltration bed runs clear, has had more than 95% of pathogens, 80% of the nitrogen, and 90% of the suspended solids removed, and has a pH closer to neutral than the original wastewater. Not too shabby, for septic effluent!
It's been years now so I'm a little foggy, but I must have first heard of worm septic systems on permies.com, which quickly led me to Anna Edey's Solviva website. Anna innovated this system in the 1990s, and Wendy Howard picked up this work and developed it into a fantastic open-source website, vermicompostingtoilets.net complete with documentation on design, construction, and maintenance. I was completely intrigued! Wastewater is processed through a septic system built around worm compost, transforming toilet and kitchen blackwater to effluent cleaner than greywater, which can then infiltrate into a green planting area. On-site, distributed sewage recycling!
Why hasn't this become the norm?? This type of septic system is being used in many countries around the world including Australia and New Zealand, but as far as we can figure out, it hasn't been permitted in any jurisdiction that we know of in the United States, except that the Hawaiian government has sanctioned some experiments with vermifiltration as a solution for their cesspool problems. Anna Edey's small household system was designed in Massachusetts decades ago... the U.S. should be at the forefront of this technology rather than waiting for a crisis to force our hand. And by the way, with all of the water issues across the Southwest, the crisis is already here, no?
Getting our conditional permit
After some research, toward the end of 2020 I made my first calls to the NM environment department to inquire about the permitting process for alternative septic systems. To make a long story short, after much more research, I submitted our ~100 page initial application in November 2021, then spent a year working with the good people in the Liquid Waste Program to figure out how to fit this highly unusual system into the permitting process. In November 2022 we had a site visit, and in December we got our conditional permit to construct! As a conditional system, we won't get our final system approval until and unless we have a year of data showing positive results. We are pleased to have that opportunity!
Our application required us to write a user manuaI -- huge thanks and kudos to Wendy Howard for her amazingly generous and thorough open-source work, which we tailored to New Mexico requirements for our application.
I will be posting separately with photos of our system build, but here's a sneak peek:
...I had originally promised Chip that if we didn't have a permit by spring 2022, I would capitulate and we could go ahead and build a conventional septic system. As it turns out the house still isn't plumbed even now, so we just kept going...
So what do you think? Do you know more about the septic situation in Hawai'i? Are they permitting vermifilter septic systems there yet? Do you know of any other permitted systems in the U.S. anywhere? Do you have any questions about worm septic? Would you consider a system like this if you were on septic? Please comment below!
...the upside of building delays...?