Designing Ecological Habitats - Gaia Education

wetlanDs for tHe ecovillage 161
at a density of around 5 plants per square metre. Cattails (Typha), reeds
(Phragmites), bulrush (Scirpus), rushes (Juncus), and sedges (Carex) are usually
the preferred species. Use locally grown and adapted plants whenever
possible. Look for wetland perennials with deep, dense, fibrous root systems
and winter tolerance. It is often possible to collect the plants from local
rivers, ponds and ditches. Otherwise they can be grown in pots while the
wetland is being constructed. Flowering plants, such as Cana Lilies, can be
installed round the edge of the wetland to add colour while harvesting cut
flowers is an added bonus. As the plants grow, it is generally good to lower
the water level in the wetland gradually using the level adjust sump. This will
encourage the plant roots to chase the water and grow deeply into the cell.
Slowly introduce the sewage so that it replaces the river water over a
week or two. It will take up to three months in summer for the system to
reach steady state at full load and longer in winter. However, the technology
will give many years’ treatment at a low operating cost. If species not planted
take over the wetland, weeding may be necessary; however, wetland species
are quite dominant, especially phragmites. If trees self seed, take them out
because the roots of large trees can penetrate the liner.
Treated effluent can be recycled for landscape irrigation, particularly
trees. Using treated effluent on vegetables is not recommended. Drip
irrigation systems are economical and can be installed without disinfecting
the treated effluent. If disinfection is required for recycling to toilets for
example, ultra-violet equipment provides a chemical-free and relatively low
impact solution.
It is good to monitor the performance of the system on a regular basis.
At a basic level this can be by testing the influent and effluent with pH and
ammonia strip testers. If a dissolved oxygen meter is available, measurements
can be taken in the level-adjust sump and the manifold cleanouts. Constructed
Gravel being installed
over geotextile and
rocks of manifold.