Designing Ecological Habitats - Gaia Education

164 Designing ecological Habitats
in this process and provide some of the endogenous sources of carbon
that support microbial life. Hollow stemmed plants, such as bulrushes and
cattails, transport oxygen to their roots, providing an aerobic environment on
the root hairs for aerobic bacteria. Plants also provide a mechanical function
by constantly forming new routes for water to flow through the wetlands.
Constructed wetlands rely on the complex ecologies of the pond, marsh,
and meadow to convert carbon and nitrogen to gaseous forms (CO 2 , CH 4 ,
N 2 ) and to redistribute the C, H, O, N, and P into more publicly acceptable
forms such as plant biomass (e.g. planted landscape and woodlands) or
animals (e.g. micro-animals and fish) rather than sludge.
Sewage contains ammonia, which is toxic to plants and is treated by
processes called nitrification and denitrification. The nitrifying bacteria,
Nitrosomonas and Nitrobacter, are responsible for the microbial conversion of
ammonia to nitrite and nitrite to nitrate. These bacteria will occur naturally
in the wetland once it reaches a steady state condition. The final step in
removing nitrogen is denitrification, which is the biological conversion of
nitrate to nitrogen gas.
Constructed wetlands have a large number of pathways, which is selforganising,
self-repairing, self-reproducing and with a great ability to adapt
to changes in influent conditions. Their benefits make constructed wetlands
an excellent sewage treatment system for ecovillages.
Michael Shaw is a founding member of The Ecovillage Institute at Findhorn and is a
resident trustee of the Findhorn Foundation. He pioneered the Ten Stones ecovillage and
cohousing community with others in Vermont, USA. An engineer by training, he has been
involved in all phases of the development and implementation of natural wastewater
treatment and bioremediation systems, including Restorers since 1989 with Ocean Arks
International (OAI). With Dr. John Todd, founder of OAI, he is the author of two wastewater
treatment patents.