We set up a simple biofilter for our greywater setup several months ago, and today took things apart to clean and look at how it was going. Our system is fairly simple, we have a kitchen sink that drains to a wicking bed that overflows to mulch pits outside. We found over several years that gunk was building up in the distribution pipes and gravel of the wicking bed and causing backup of water.
So, we made a filter. We started with mesh filters, and the regular cleaning and maintenance didn't do what we wanted, so we tried a biofilter. The biofilter is basically woodchips and earthworms, the idea being that the worms will eat food particles and junk before it gets to the wicking bed. It's a 2 stage filter, with stage one being right under the sink, and stage 2 being at the inlet of the wicking bed.
Overall, it was really successful, and today we cleaned out part of the vermicompost in the filters and added new woodchips. I think we may do this every 2-3 months for stage 1 filter and every 6 months for stage 2. When we clean it, we only remove part of the old wood chips, really just the bottom part which are mostly rotted and turned to vermicompost.
I recently installed a "dark grey water" system for my kitchen sink. Right now, there seems to be two schools of thought on biofilter/no biofilter. My system bypassed the biofilter (although there's still room to add one if necessary). I opted out because of reported smells. And I'm careful about putting grease down the system. My system is VERY NEW so no problems yet. Time will tell.
Very interested in hearing updates on how this works out for you over time.
Subtropical desert (Köppen: BWh)
Elevation: 1090 ft Annual rainfall: 7"
Location: Chihuahua Desert
posted 6 years ago
We haven't had any smells with this one. We last opened it up about 3 months ago. It's been running for almost 5 months.
We try and strain out big stuff, but inevitably, there is stuff that gets by, and that's really why we have the biofilter. Our wicking bed system eventually backed up and we had to clean it out, which was nasty as hell! So, I know what years of little bits of stuff getting by can eventually do. But, this seems to work great. The second stage had no noticeable grease, and I opened up the wicking bed inspection, and everything looked great and water flowed through the system beautifully.
There weren't any other critters in there, just earthworms. And while we were inspecting it and taking photos, we had hens that really wanted to get in there and get to the worms. But, we didn't let that happen, and the spent filter material went to our flow-through worm bin to save any eggs or worms that might still be in there.
We will certainly post updates about it as it goes. If I had to change anything, it would be to make things a bit easier to get in and out, but generally, it works great.
Wondering if you would send an update on your biofilter, including how often you've had to clean it out? Also, can you describe the design in a bit more detail? I see the screens and the box of woodchips/worms, but am unclear about where the screens go (does water filter through the screens before hitting the woodchip box?). How big is the woodchip box? Does it drain into a pipe? How many folks are using the sink (i.e. 2 adults, full time, etc.). Anything you can provide would be helpful - I'm trying to design something for my off-grid yurt... because of high water table, we can't go directly from sink into an in-ground mulch basin, so will go through biofilter, then container-wetland, then into mulch basin.
Thanks for any tips/design info you can provide!
Location: Chihuahua Desert
posted 5 years ago
The biofilter works good, we clean it out every 4 months or so. The design is fairly simple, it's a rubbermade box with a vegetable crate inside. We line the sides of the crate with some vinyl, and then fill it with wood chips and worms. The rubbermade box has a drain going to the greywater pipe, and the sink drains to the top of the box. The screens are under the woodchips to keep them from draining away.
The wood chip box is about 18" by 12" by 12" deep. If we had more space, I'd go with a bigger box, more surface area is better, probably twice this size. I think if you get the surface area right, you won't ever have to clean it.
This sink is in our kitchen, 2 adults, 2 kids. We do dishes every day, wash hands, things like that.
Abe! thanks for your post/blog. i'm also in the chihuahuan desert. gonna try this bio-filter. a few questions if you don't mind. what do you use for filter material? (looks like straw) what would happen if they were exposed to cold weather? i'm off grid and my trailer isn't heated, was actually thinking about doing this outside. on your blog there are pictures of a steel sink with a filter in it, is that above the biofilter? cheers,
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