Introduction

Whole Systems Approach to Ecological Design

Appropriate Technology: Water

Organic Agriculture and Local Food

Appropriate Technology: Energy

Green Building & Retrofitting

Plant Rhizospheres

All of the processes described above are microbial.  In order for the necessary microbes to thrive appropriate habitats must be created within the treatment systems.  Plants and artificial media (gravel and sand) are used in natural treatment systems to create the media necessary to support rich microbial communities.  Nitrification of ammonia to nitrates occurs in the biofilms, which attach to the media.  The root zones of the higher plants play a central role in this process and provide some of the endogenous sources of carbon that support the biological systems.

The extensive root network or rhizosphere in the planted ecologies provides the structure and nutrient support for diverse microbial communities.  Materials from the plant roots are exuded into the surrounding rhizosphere.  These materials include hormones, antibiotics, metal chelators, nutrients, humic compounds and polysaccharide glues (Todd et al, 1996).

Plants also provide a mechanical function by constantly forming new pathways in the SSFCWs, through which water can filter.  This keeps the wetlands open to the flow of water.  Some plants also possess the ability to transfer oxygen from their aerial stems to their roots.  This continuous exposure of organic matter to air promotes the decomposition and oxidation of the organic matter and enhances nitrification.

• Anaerobic Digestion
• Aerobic digestion
• Nitrification
• Denitrification
• Plant Rhizospheres

Carbon Cycle in Constructed Wetlands
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