Subject: (fwd) Re: Grey Water

From: [email-masked]
Date: Thu, 15 Feb 2001 19:34:55 -0500

On Thu, 15 Feb 2001 23:21:07 GMT, in alt.permaculture "Reedbed"
<[email-masked]> wrote:

Haig <[email-masked]> wrote in message
news:[email-masked]...
> Mark,
>
> my understanding is that any biological nutrient system is dependent on
the
> food requirements of the species chosen. Apart from the micro nutrients
> (trace elements), living organisms need a balance of their major nutrients
> (N, P, K, C, etc) to grow and reproduce. This introduces the concept of a
> "limiting nutrient",

Thanks for that - obvious really, when you explain it that way - but I
think
I misread your original post, thinking that you meant that N and P are
_chemically_ dependant on each other.
From my own reading of the situation, reed bed systems themselves are
not
great at removing P over long periods. However, the removal mechanisms
are
not _all_ biological. (Biological P removal can be in the range of 30
to
50%). Gravel-based beds are better than soil, but P removal depends on
the
iron content of the substrate, and eventually reaches saturation.
Most of the long term P removal is best carried out after the
treatment
system in a soil-based leachfield or a wet woodland, where adsorption,
complexation and precipitation are enhanced by a high clay content -
using a
mixture of plant/grass species, P removal can reach 99%.

Low-P and no-P washing powders, cleaners etc are fairly common
nowadays, and
are a Good Thing - whatever the eventual method of wastewater
treatment.

Mark