Wastewater Worm Composting

Collecting different types of greywater for my Backyard Vermi-Filtration System in recent weeks has been an eye-opening experience. It has made me realize not only just HOW MUCH water we use for rinsing dishes etc, but also how much potential worm nutrition has been ending up down the drain over the years!

During the colder months of the year, without any sort of legitimate greywater system installed, there’s not a whole lot we can do other than making an effort to be more mindful about various forms of water-use. But from spring through fall there’s really no excuse for not taking advantage of this resource (and I am kicking myself for not really thinking of it before).

Initially, the idea was simply to pour all this wastewater into the vermi-filtration system, but I realized fairly quickly that it would likely be overkill – especially early on, before a rich microbial bio-film and worm population was established. Aside from this, constantly carrying buckets out to the system is a bit of a hassle.

Surprisingly enough (given my years of experience with decomposition) I thought I might be able to store the wastewater in an empty plastic garbage can before use (the way I do with extra rain water). Didn’t take me long to realize that was a dumb idea – all those nutrients in water with zero aeration led to a foul, anaerobic situation very quickly.

Then it hit me…

Why do I need to add it all to the vermi-filtration system when I have 8 or 9 decent sized active outdoor vermicomposting systems on the go in my yard? The funny irony is these outdoor systems can start to get a bit unwatered (and even underfed) during the summer months!

The “rules” for what type of wastewater is acceptable are susprisingly similar to those for adding solid wastes to a worm bin – maybe even a bit more relaxed given how much water is diluting certain potentially-harmful components.

Here are some of the common examples:

– Rinse water from cups, bowls, plates, cutting boards, beverage/food containers cookware and cutlery.
– Vegetable/salad cleaning water
– Basic hand rinse water (NO soap)
– Leftover water in re-usable water bottles
– “Syrup” from salt-free canned legumes (even diluted I’ve decided it’s best not to use the salted version)
– Some leftover coffee (am a bit careful about this one)
– Vegetable cooking water (cooled off of course)

In terms of quantity, I would estimate that I am ending up with at least 3 or 4 small buckets (~ 3 gal pail) of this water a day. I like to put at least one bucket through the vermi-filter each day, but most of it is now ending up in my various outdoor systems. Might not sound like all that much, but over time it can add up to a LOT of extra moisture/nutrition – especially versus not doing it at all.

An approach like this works especially well when you are a bit heavy-handed with the paper waste bedding materials like shredded cardboard/paper/newsprint, particularly when you have concentrations of bedding down in the lower reaches of your systems. They soak up (and hold) liquids, becoming a fantastic long-term food source – more and more nutritious over time.

I’ve really only just gotten started, but I’m very optimistic that this will have a major positive impact on my outdoor systems and the success of my “worm herd” as a whole.
Will keep everyone posted!

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    • Devin Dekoekkoek
    • October 21, 2020

    Iā€™d love to know how this turns out! Also, what method are you using to collect the waste water?

    And, what specifically do you mean by your vermi filtration system?

    Thank you, very much!

    • Bentley
    • October 23, 2020

    Hi Devin – I am hoping to take the system down (and provide an update) fairly soon. Water collection was pretty basic – I had a bowl I would keep in my sink and basically just rinse plates etc into.
    Vermi-filtration involves the passage of nutrient-rich liquids through an active (although somewhat modified) vermicomposting system – a lot of the nutrients etc are removed and you end up with cleaner – potentially “enhanced” (for plant growing) water coming out from the bottom.

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