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[permaculture] Living Technologies website (John Todd of New Alchemy Institute)
Thanks for the URL, Helen,
John Todd et al have indeed done some interesting work with water
purification (including removal of heavy metals) using algae and water
plants. They've to some extent focused on treatment of seriously polluted
water, as opposed to normal, household black and grey water streams. To me,
what this means is that 1) the systems are technical and
materials-intensive as compared to what a pc'er might contemplate for a
home 'waste' system, and )2 the nutrients are disposed of instead of used
most efficiently with an eye toward productivity.
The very idea of 'waste', in fact, leads to 'treatment of wastes' instead
of 'use of resources'. In practical terms, this means that the value of the
wastes (ie, as fertilizers) is purposely dissipated and 'disposed of'
instead of being taken advantage of. This is how we treat rural waste
streams, with septic tanks and leach fields that dispose of the effluent
without regard for its value. This is also true of constructed wetlands,
where most of the nutrient value of a waste stream is absorbed and
dissipated by bacteria in gravel beds, as opposed to being used for
production. Better than a leach field (nitrates are better kept out of
groundwater), but not using the nutrients to best advantage.
I think it makes better sense, on a practical home-based level, to consider
systems which treat dissolved nutrients as resources and use them
productively instead of dissipating them. These would include: hydroponic
systems which use septic tank effluent to fertilize plants growing in
gravel beds (kind of high-tech); systems which use septic tank effluent as
sprays or sub-surface irrigation to grow trees or mulches (mid-tech); and
composting toilets (nice, low-tech -- yea!).
Todd et al do use the nutrients in their systems for feeding fish and other
aquatic organisms of value, and a similar setup exists in hybrid aquaponics
systems where fish in intensive cultivation have their water cleaned by
being run through growing beds of veggies/herbs in gravel growing media (at
about 3:1 growing beds:fish tank, measured as surface areas -- see
http://www.townsqr.com/snsaqua/ for an overview of commercial systems).
Lots of possibilities, all probably best guided by remembering that septic
wastes are agriculturally very valuable -- human waste treatment streams,
in fact, pose one of the largest gaps between what we take and what we
return from our ecosystems, and are a major waste of valuable phosphorous.
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