Introduction

Whole Systems Approach to Ecological Design

Appropriate Technology: Water

Organic Agriculture and Local Food

Appropriate Technology: Energy

Green Building & Retrofitting

Building Constructed Wetlands

Horizontal flow constructed wetlands for treating wastewater need a pre-treatment stage to lower influent BOD (Biochemical Oxygen Demand) and TSS (Total Suspended Solids), otherwise the wetland can get overloaded at the front end, which can cause clogging.  Correct dimensions are also essential, with the length to breadth ratio no greater than 2:1.

Click on image to enlarge

For small to medium sized systems (<2,000 pe (person equivalents)) septic tanks can be cost effective.  For large system pre-treatment can be with a primary clarifier of roughing filter.

Sketch of Roughing Filter by Natural Systems International

It is essential to size constructed wetlands correctly.  The determining factors are flows, influent loadings, water temperature and effluent quality required.

Septic tanks need to be emptied when they become two-thirds full of settled sludge.  A cost effective treatment technology is a Vertical Flow Reed Bed.

• Biological Processes in Wastewater
• Building Constructed Wetlands
  • Septic Tanks
  • Sub-Surface Flow Constructed Wetlands
  • Sizing of Wetlands
  • Vertical Flow Reed Bed