Comments on: DIY Reedbed for Treating Our Household Grey Water for Under $500

By: Craig

Craig — Thu, 03 Nov 2016 17:11:44 +0000

I can't remember where I first saw the idea but it's similar to the ECO design aerobic grease filter that's filled with compost and starter worms at the bottom of the page here: https://damnthematrix.wordpress.com/2015/03/04/sustainable-greywater/
The design I remember fed the outflow into a bioretention system like yours rather than straight to the lawn via what they call pots that distribute the water.

By: Morag Gamble : Our Permaculture Life

Morag Gamble : Our Permaculture Life — Wed, 26 Oct 2016 05:54:25 +0000

Thanks – so many interesting questions. Lots more to explore – as always!
Just wondering where the lead comes from in the worm farms.

By: Morag Gamble : Our Permaculture Life

Morag Gamble : Our Permaculture Life — Wed, 26 Oct 2016 05:50:52 +0000

Hi Michelle, Lovely to hear from you! The overflow currently goes to a banana circle. There are designs for it to have underground piping but to be honest, because we are conservative in our use, that seems to cope extremely well.

By: Michelle Maher

Michelle Maher — Sat, 22 Oct 2016 09:05:45 +0000

Hi Morag. Previous PDC graduate of yours (1999) here, and a past designer of sustainable on-site wastewater systems. Great reedbed. Did you incorporate an overflow at the end?

By: Craig

Craig — Fri, 21 Oct 2016 23:05:45 +0000

Bioretention systems are great, I was only reading about their standardisation and use for storm water management the other day after watching a few of Ideanthro's videos on YouTube.
I do question monocultures in these systems however, and as I suggested to him, diversity in the plant species and rhizosphere would aid in hosting more biological diversity needed to recycle all kinds of compounds and keep the soil, soil community and human pathogens in check.
And while they have a lot of positives, after a lot of reading I still have niggling concerns about any closed/lined biofiltration system that concentrates material in the one place, and worry some of these systems are building up toxins over the longer term if they aren't designed well, managed, harvested and distributed, then refreshed like you would changing a used drinking water filter. Especially rain gardens fed from roofing and the build up of heavy metals in those soils.
After a question on Twitter and lots of Google scholar and calculations later, I also learned that even repeated vermicomposting can increase lead levels in some species of worms and castings that are borderline when compared with Australian recommendations for safe physical handling of soil lead levels, let alone feeding of the worms to chooks. I've also seen vermicompost systems used for bioretention of household greywater that periodically get harvested, spread and replenished, just like replacing a filter, and that may be an alternative approach.
I also learned last week that during wind events and soils watered with wastewaters that up to 15% of viruses in one study were aerosolized and 89% of that can happen in 30 mins, so wastewater irrigation of soils exposed to wind is a bad idea, and reeds or other kinds of wind breaks in bioretention systems are a great idea. It'd be interesting to know if fans like used in your humanure compost system also have the potential to aerosolize any pathogens. I doubt that's ever been studied.