Introduction

Whole Systems Approach to Ecological Design

Appropriate Technology: Water

Organic Agriculture and Local Food

Appropriate Technology: Energy

Green Building & Retrofitting

Ecological Engineering for Water

For wastewater treatment, the “tool box” is typically plants, microorganisms, filtering animals and fungi.  The process is a breakdown process with a minor secondary uptake process.  The bacteria break down the long-chain organic molecules into simple non-polluting substances.  A small amount of nutrients – nitrogen and phosphorus – is taken up by the plants, which is typically less than 5% of the treatment.  It is the root mass of the plants that is important. Biofilms grow on the roots so enabling “attached growth treatment”.  Free-swimming bacteria are also present, which provide “suspended growth treatment”.

Attached growth on a live substrate significantly increases the efficiency and stability of the biofilm. The biofilms are grased by the microanimals shown in the chart in the next page (see Constructed Wetlands Treatment).  By maximising attached growth treatment, the amount of dead bacteria or “sludge” in the system is minimised.

Sketch from Constructed Wetlands in the Sustainable Landscape, by Ogden and Campbell.
Click on image to enlarge

• The Hydrological Cycle
• Ecological Engineering for Water

Biofilms grow on the roots

Biofilm under an electron microscope.